JP6727047B2 - Display device - Google Patents

Description

The present invention relates to a display device, and more particularly to a technique for controlling brightness correction of an image displayed by the display device.

2. Description of the Related Art Display devices configured using LEDs as pixels are widely used for outdoor and indoor advertisement display and the like due to technological development of LEDs (Light Emitting Diodes) and cost reduction. Until now, these LED display devices have mainly been used for displaying moving images such as natural images or animations. In recent years, as the pixel pitch has become narrower, LED display devices have been used for indoor displays with a short viewing distance, such as conference room displays and monitoring video display displays. Among such display devices for indoor use, LED display devices for monitoring often display a moving image in a part of the display area like a personal computer image and a still image in most of the other display areas.

Patent Document 1 discloses a display device that realizes power saving by suppressing an increase in power supply capacity. The display device described in Patent Document 1 predicts the current value flowing through the display panel based on the input video signal. Then, when the sum of current values in frame units becomes equal to or greater than a predetermined threshold value, the display device corrects the video signal processing, that is, the contrast and brightness of the image, and the current value flowing in the display panel reaches a predetermined maximum value. Control not to exceed.

Japanese Patent No. 4808913

In the power control performed by the display device described in Patent Document 1, when the image displayed on the display panel is a moving image, the image quality deterioration due to correction is not noticeable, but like a personal computer image, a part is a moving image and most is a still image. When a certain image is corrected, there is a problem that the gradation of the image is lowered depending on the degree of the correction, and the deterioration of the image quality is noticeable.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a display device that performs power saving control such that deterioration of image quality of a still image is not noticeable.

In the display device according to the present invention, an image based on a video signal is sequentially displayed for each frame, a display unit including a video display area and a correction area provided in a part of the video display area, and a display area is displayed in the correction area. The brightness correction control unit includes a brightness correction control unit that corrects the brightness of an image for each frame, and the brightness correction control unit calculates a brightness information from a video signal for displaying an image in the correction area, and a brightness information calculation unit based on the brightness information. A correction coefficient calculation unit that calculates a correction coefficient, a correction calculation unit that corrects a video signal that displays an image in the correction area with a brightness correction coefficient, and brightness information in each correction area that is calculated for each frame by the brightness information calculation unit. And a moving image determination unit that determines whether or not the difference is greater than or equal to a predetermined difference. The correction calculation unit corrects the video signal for displaying the image in the correction area when the moving image determination unit determines that the difference is equal to or more than the predetermined difference. When displaying an image in the video display area, the display unit displays in the correction area an image based on the video signal corrected by the brightness correction control unit for each frame.

According to the display device of the present invention, it is possible to provide a display device that performs power saving control such that deterioration of image quality of a still image is not noticeable.

FIG. 3 is a functional block diagram showing the configuration of the LED display device in the first embodiment. FIG. 3 is a diagram showing a video display area and a correction area in the first embodiment. FIG. 3 is a diagram showing a configuration of a processing circuit according to the first embodiment. 3 is a timing chart showing an example of PWM driving in the first embodiment. 6 is a flowchart showing a brightness correction control operation in the first embodiment. FIG. 6 is a diagram showing a relationship between a brightness correction coefficient and an average pixel value in the first embodiment. FIG. 6 is a schematic diagram showing luminance of a frame and a correction area in the first embodiment. FIG. 7 is a functional block diagram showing a configuration of an LED display device according to a second embodiment. 9 is a flowchart showing a brightness correction control operation in the second embodiment. 9 is a flowchart showing a brightness correction control operation in the second embodiment.

An embodiment of a display device according to the present invention will be described. In the following first and second embodiments, as an example of the display device according to the present invention, an LED display device in which a plurality of LEDs are arranged in a matrix and each LED is controlled to blink to display video information. An embodiment will be described.

<Embodiment 1>
(Configuration of LED display device)
FIG. 1 is a functional block diagram showing the internal configuration of the LED display device according to the first embodiment. As shown in FIG. 1, the LED display device according to the first embodiment includes an input terminal 1 for inputting a video signal from the outside and an effective area required for display from the input video signal, and a gamma of an image to be displayed. A video signal processing circuit 2 that performs processing such as correction, a brightness correction control circuit 10 that corrects the brightness of an image based on the video signal, a display unit 20 that displays an image or a video, and a drive circuit that drives the display unit 20. 3 and 3.

In the first embodiment, the display unit 20 has a plurality of pixels arranged in a matrix in the video display area, and one set of pixels has different emission colors of red (R), green (G), and It is composed of three blue (B) LEDs. The display unit 20 shown in FIG. 1 illustrates a display unit including 4 pixels×4 pixels=16 pixels. Each pixel included in the display unit 20 has each pixel value, and these pixel values correspond to the gradation of the brightness of the image based on the video signal. In the first embodiment, each LED that constitutes each pixel also has a pixel value.

FIG. 2 is an example of the display unit 20 having an input resolution of 1920 pixels×1080 pixels, and the display unit 20 is composed of 1920 sets×1080 sets of LEDs. In FIG. 2, the display unit 20 has a video display area 21 of 1920 pixels×1080 pixels, and an image based on a video signal is sequentially displayed in the video display area 21 for each frame. The display unit 20 also includes a correction area 22 provided in a part of the video display area 21. In the coordinates representing the position in the image display area 21 of FIG. 2, the area having diagonal lines from (640, 360) to (1920, 1080) is the correction area 22. In the first embodiment, the correction area 22 can be designated by the user. The user designates a desired area in the image display area 21 from the area input section 4 provided in the LED display device.

Next, a configuration for realizing the function of the LED display device for correcting the brightness or the dynamic range of the image displayed in the correction area 22 for each frame will be described. As shown in FIG. 1, the LED display device includes a brightness correction control circuit 10. The brightness correction control circuit 10 includes an area setting unit 11 that sets the area designated by the area input unit 4 as the correction area 22. Further, the brightness correction control circuit 10 determines whether the video signal input from the video signal processing circuit 2 is a video signal for displaying an image in the correction area 22 based on the position information of the correction area 22 output from the area setting unit 11. It further includes an area determination unit that determines whether or not the brightness correction control circuit 10 in the first embodiment includes a first area determination circuit 12 as one of the area determination units. The correction area 22 may be a predetermined area, and in that case, the LED display device does not need to include the area input unit 4 and the area setting unit 11. In that case, the first area determination circuit 12 reads the position information of a predetermined correction area stored in advance in a memory or the like and uses it for the determination operation.

Further, the brightness correction control circuit 10 determines the brightness information from the video signal displaying the image in the correction area 22 among the video signals input from the video signal processing circuit 2, based on the determination result output from the first area determination circuit 12. The brightness correction control circuit 10 further includes a brightness information calculation unit for calculating, and in the first embodiment, the brightness correction control circuit 10 includes a brightness information calculation circuit 13 as the brightness information calculation unit. The brightness information calculated by the brightness information calculation circuit 13 is, for example, the sum of the pixel values of the pixels included in the correction area 22 or the average pixel value in the correction area 22. Further, the brightness correction control circuit 10 further includes a correction coefficient calculation unit that calculates a brightness correction coefficient based on the brightness information output from the brightness information calculation circuit 13. In the first embodiment, the brightness correction control circuit 10 includes: and a correction coefficient calculating unit including a correction coefficient calculation circuit 14.

In addition, the brightness correction control circuit 10 further includes a frame memory 15 that temporarily stores the video signal output from the video signal processing circuit 2 and is controlled so as to be read at a timing required by the display unit 20. .. The brightness correction control circuit 10 further includes an area determination unit that determines whether the video signal read from the frame memory 15 is a video signal for displaying an image in the correction area 22. In the first embodiment, the brightness correction control circuit 10 includes a second area determination circuit 16 as an area determination unit, in addition to the first area determination circuit 12. Further, the brightness correction control circuit 10 causes the correction coefficient calculation circuit 14 to determine a video signal for displaying an image in the correction area 22 among the video signals input from the frame memory 15 based on the determination result of the second area determination circuit 16. It further includes a correction calculation unit that performs correction according to the output brightness correction coefficient. In the first embodiment, the brightness correction control circuit 10 includes a correction calculation circuit 17 as a correction calculation unit. The correction calculation circuit 17 multiplies the brightness signal included in the video signal by the brightness correction coefficient, for example. The brightness signal is, for example, each pixel value included in each pixel included in the correction area 22. The corrected video signal is output to the drive circuit 3. When the display unit 20 displays an image in the video display area 21, the drive circuit 3 causes the display unit 20 to display an image based on the video signal corrected for each frame by the brightness correction control circuit 10 in the correction area 22. To drive.

(Brightness correction controller)
As described above, the brightness correction control circuit 10 shown in FIG. 1 individually includes each circuit for correcting the video signal for displaying the image in the correction area 22 by the brightness correction coefficient. If each circuit is dedicated hardware, then each circuit is, for example, a programmed processor or a parallel programmed processor. In addition, the brightness correction control circuit 10 may realize each function of each circuit by including dedicated hardware in which each circuit is integrated.

Further, the LED display device may realize each function of each circuit included in the brightness correction control circuit 10 by software. In that case, the LED display device includes a processing circuit 19 as illustrated in FIG. 3A, and the processing circuit 19 includes, for example, a processor 19a and a memory 19b that are connected to each other as illustrated in FIG. 3B. including. The processing circuit 19 has an input side connected to the video signal processing circuit 2 and an output side connected to the drive circuit 3. The processor 19a has a function of executing a program stored in the memory 19b. The pro gram stored in the memory 19b, the following brightness correction control function is described. The processing circuit 19 sets the area designated by the area input unit 4 as the correction area 22. The processing circuit 19 inputs the video signal output from the video signal processing circuit 2 and determines whether the video signal is a video signal for displaying an image in the correction area 22. Based on the determination result, the processing circuit 19 calculates the luminance information from the video signal that displays the image in the correction area 22 among the video signals input from the video signal processing circuit 2. The processing circuit 19 calculates the brightness correction coefficient based on the calculated brightness information. The processing circuit 19 determines whether the video signal read from the frame memory 15 is a video signal for displaying an image in the correction area 22. Based on the determination result, the processing circuit 19 corrects the brightness of the video signal for displaying an image in the correction area 22 among the video signals input from the frame memory 15 with the brightness correction coefficient calculated previously. The processing circuit 19 reads the program in which the above-described brightness correction control function is described from the memory 19b and executes it by the processor 19a. As described above, the LED display device realizes the brightness correction control function by software. The function of the frame memory 15 may be replaced by the memory 19b. Further, in the LED display device, as for each function and each operation included in the brightness correction control circuit 10, a part thereof may be realized by dedicated hardware and a part thereof may be realized by software.

(Brightness control method by PWM)
A method for adjusting the brightness when the LED display device displays an image on the display unit 20 will be described. The drive circuit 3 of the LED display device according to the first embodiment adjusts the brightness by driving the display unit 20 by the PWM (Pulse Width Modulation) method. FIG. 4 is a timing chart showing an example of PWM driving. FIG. 4A shows one frame of a video signal which is the basic cycle of PWM. FIG. 4B shows an example in which the duty ratio of the current pulse width with which the drive circuit 3 conducts the LED is 100%, and the current pulse width is one frame period or less of the video signal. FIG. 4C shows an example in which the duty ratio of the current pulse width is 75%. In the PWM drive of FIG. 4C, the duty ratio is smaller than that of FIG. 4B, and the brightness is dark because the LED energization time is short in one frame. The LED display device adjusts the brightness of each LED by changing the duty ratio of the current pulse width within one frame. In addition, the PWM drive in FIG. 4C consumes less power because the LED energization time is shorter than that in FIG. 4B. As described above, the magnitude of the PWM duty ratio is related to the brightness and the power consumption. Therefore, the smaller the brightness value of the video signal, the smaller the duty ratio, and the smaller the power consumption consumed by the LED. On the other hand, the larger the brightness value of the video signal, the larger the duty ratio and the consumption consumed by the LED. The electric power becomes large. The power consumption in the PWM drive with the duty ratio of 75% shown in FIG. 4C is 75% of the power consumption in the PWM drive with the duty ratio of 100% shown in FIG. 4B.

(Brightness correction control operation)
The brightness correction control operation for power saving control of the LED display device according to the first embodiment will be described with reference to the block diagram of FIG. 1 and the flowchart of FIG. From the area input unit 4 shown in FIG. 1, the user specifies an area for which image correction is desired. The area input unit 4 outputs the position information of the designated area to the area setting unit 11, and the area setting unit 11 sets the designated area in the correction area 22 (step S1). The position information of the correction area 22 set by the area setting unit 11 is output to the first area determination circuit 12 and the second area determination circuit 16.

The first area determination circuit 12 and the frame memory 15 receive the video signal from the video signal processing circuit 2 (step S2).

The first area determination circuit 12 determines whether the input video signal is a video signal for displaying an image in the correction area 22 based on the position information of the correction area 22 output from the area setting unit 11 ( Step S3). If NO in step S3, that is, if the video signal is a video signal for displaying an image in the video display area 21 different from the correction area 22, the LED display device performs the brightness correction control according to the first embodiment. The operation is not performed, and the process proceeds to step S9. If YES in step S3, that is, if the video signal is a video signal for displaying an image in the correction area 22, the first area determination circuit 12 sends the determination result to the luminance information calculation circuit 13 together with the video signal. Output.

The brightness information calculation circuit 13 calculates the brightness information in the correction area 22 for each frame from each pixel value included in each pixel included in the video signal (step S4). In the first embodiment, the brightness information is an average pixel value per LED included in the correction area 22. When the total number of pixels included in the correction area 22 is num, and the pixel values of the R, G, and B LEDs included in the correction area 22 are Ri, Gi, and Bi, respectively, the average pixel value AveRGB is given by Equation 1 Is calculated by In the first embodiment, each of the R, G, and B LEDs of the LED display device has a pixel value of 8 bits, that is, a pixel value of 256 gradations. Therefore, the maximum value that the average pixel value can take is 255. The brightness information calculation circuit 13 outputs the calculated average pixel value to the correction coefficient calculation circuit 14 as brightness information.

The correction coefficient calculation circuit 14 determines whether the average pixel value calculated by the brightness information calculation circuit 13 is equal to or larger than a predetermined threshold value (step S6). A threshold average pixel value 192 is set as a predetermined threshold in the correction coefficient calculation circuit 14 of the first embodiment.

When the average pixel value is less than the predetermined threshold value, that is, when NO in step S6, the correction coefficient calculation circuit 14 assigns a brightness correction coefficient whose brightness does not change even after the correction of the video signal (step S7). FIG. 6 is an example of the brightness correction coefficient calculated and output by the correction coefficient calculation circuit 14 in the first embodiment, and the horizontal axis represents the average pixel value calculated by the brightness information calculation circuit 13. In the first embodiment, the threshold value of the average pixel value is set to 192 as an example, and when the average pixel value is less than 192, the correction coefficient calculation circuit 14 sets the brightness correction coefficient to 1 as shown in FIG. Assign This is because the brightness correction performed by the correction calculation circuit 17, which will be described later, is a correction for multiplying the video signal by the brightness correction coefficient. Therefore, if the brightness correction coefficient is 1, the corrected brightness does not change even if the multiplication is performed. ..

On the other hand, when the average pixel value is equal to or larger than the predetermined threshold value, that is, when YES in step S6, the correction coefficient calculation circuit 14 calculates and assigns the brightness correction coefficient (step S8). That is, in the first embodiment, the correction coefficient calculation circuit 14 calculates the brightness correction coefficient when the average pixel value is 192 or more.

In the first embodiment, as shown in FIG. 6, when the average pixel value is 192 or more, the correction coefficient calculation circuit 14 corrects the brightness of the image displayed in the correction area 22 after correction by the correction calculation circuit 17. A brightness correction coefficient that reduces the brightness of the image based on the previous video signal is calculated. In the brightness correction by the correction calculation circuit 17, which will be described later, the brightness correction coefficient is multiplied by the video signal to correct the brightness. Therefore, the correction coefficient calculation circuit 14 calculates the brightness correction coefficient to be 1 or less.

Further, in the first embodiment, the correction coefficient calculation circuit 14 calculates the brightness correction coefficient according to the size of the average pixel value such that the brightness correction coefficient decreases as the average pixel value increases. That is, as shown in FIG. 6, as the average pixel value increases from 192 to 255, the calculated brightness correction coefficient gradually decreases.

Further, the correction coefficient calculation circuit 14 adjusts the value of each brightness information before correction so that each brightness information of each image based on the video signal corrected for each frame by the correction calculation circuit 17 has a predetermined value. Then, the brightness correction coefficient is calculated. In the first embodiment, the correction coefficient calculation circuit 14 calculates the brightness correction coefficient such that each average pixel value of each image in the correction area 22 based on the video signal corrected by the correction calculation circuit 17 becomes 192. To do. For example, when the average pixel value of the image before correction is 255, the correction coefficient calculation circuit 14 calculates the brightness correction coefficient 0.75, and when the average pixel value of the image before correction is 200, for example, the correction is performed. The coefficient calculation circuit 14 calculates a brightness correction coefficient 0.96. Note that these calculations are executed by, for example, the correction coefficient calculation circuit 14 reading a predetermined calculation formula or a predetermined table stored in advance in a memory or the like.

For example, when the brightness correction coefficient is Mul, Mul is calculated by Expression 2.

In step S2, the video signal output from the video signal processing circuit 2 is also stored in the frame memory 15 in accordance with the horizontal and vertical synchronizing signals of the video signal, and is read out one frame later at the timing required by the drive circuit 3. In the first embodiment, data is read one frame after the video is written in the frame memory 15, and the second area determination circuit 16 inputs the video signal from the frame memory 15 (step S9).

Subsequently, the second area determination circuit 16 determines whether the video signal is a video signal for displaying an image in the correction area 22 (step S10). The position information of the correction area 22 is a value output by the area setting unit 11 in step S1. If the video signal is a video signal for displaying an image in the video display area 21 different from the correction area 22, that is, if NO in step S10, the LED display device does not perform the brightness correction control operation, and thus step S12 is performed. Move to. If the video signal is a video signal for displaying an image in the correction area 22, that is, if YES in step S10, the second area determination circuit 16 outputs the video signal to the correction calculation circuit 17 together with the determination result. To do.

The correction calculation circuit 17 is a video signal for displaying an image in the correction area 22 among the video signals output from the frame memory 15 and input through the second area determination circuit 16 based on the determination result of the second area determination circuit 16. The brightness is corrected by the brightness correction coefficient output from the correction coefficient calculation circuit 14 (step S11). More specifically, the correction calculation circuit 17 multiplies the video signal for displaying an image in the correction area 22 by the brightness correction coefficient calculated by the correction coefficient calculation circuit 14. In the first embodiment, the video signal multiplied by the brightness correction coefficient by the correction calculation circuit 17 is a brightness signal included in the video signal, or image data related to brightness for displaying an image. That is. As an example, in the first embodiment, the correction calculation circuit 17 multiplies each pixel value by the brightness correction coefficient.

The correction arithmetic circuit 17 outputs a control signal for displaying the corrected image in the correction area 22 and the image without correction in the video display area 21 outside the correction area 22 to the drive circuit 3, and the drive circuit 3 The display unit 20 is driven based on the control signal. That is, the drive circuit 3 PWM-controls each LED of the display unit 20 based on the control signal, and displays a corrected image in the correction area 22 and an uncorrected image in the video display area 21 outside the correction area 22. Yes (step S12).

As described above, in the first embodiment, the correction coefficient calculation circuit 14 calculates the brightness correction coefficient so that each average pixel value of each image displayed in the correction area 22 after the correction of the video signal becomes 192. doing. For example, when the average pixel value included in the video signal before correction is the maximum of 255, that is, when all the LEDs in the correction area 22 are turned on at the duty ratio of 100%, the correction coefficient calculation circuit 14 calculates The brightness correction coefficient to be assigned is 0.75 as shown in FIG. After correction by the correction calculation circuit 17, the average pixel value in the correction area 22 becomes 192. That is, all the LEDs in the correction area 22 are turned on with a duty ratio of 75%. As a result, the consumption current consumed by the LEDs in the correction area 22 is limited to 75% as compared with that before the correction, and the LED display device can reduce the power consumption.

(effect)
As described above, the LED display device monitors the video signal in the correction area 22 designated by the user, and if the average pixel value in the correction area 22 is larger than the preset threshold value, the power consumption increases. It is possible to judge and control so that the power consumption does not exceed a certain value. Therefore, when the power consumption of the correction area 22 increases, the LED display device can instantaneously reduce the brightness of the image to a predetermined brightness for each frame. FIG. 7 is a schematic diagram in which a video composed of nine frames including the video display area 21 and the correction area 22 of FIG. 2 is separated into images for each frame and arranged in time order. For example, when the correction areas 22 of the three frames shown in the center are too bright or the power consumption is equal to or higher than a predetermined value, the LED display device according to the first embodiment can reduce the brightness by the power over. As a result, the LED display device can suppress the peak power without causing the user to feel a decrease in brightness, and a greater power saving effect than before can be exhibited in an operational application in which the operating time of one day is long.

Further, when operating the LED display device for monitoring purposes, most of the displayed video is a still image, and a moving image is often displayed in a part of the still image. When the image displayed by the LED display device is a still image, the LED display device performs power control for correcting the brightness of the entire image display area based on the average pixel value of the image signal for displaying the image in the entire image display area. In this case, the power consumption of the LED display device can be reduced. However, since the dynamic range is narrowed, the output gradation of the luminance of the video display area is collapsed, which causes a visual problem when displaying a still image. On the other hand, when the image displayed in the video display area is a moving image, even if the luminance of the entire video display area changes instantaneously or the dynamic range narrows, the problem is not easily visible. Therefore, the user designates the area for displaying the moving image as the correction area 22 in advance, and the LED display device performs the power control by the brightness correction control operation in the designated correction area 22. It is possible to perform power control while maintaining the image quality of.

Further, when a moving image is displayed on a part of the still image of the video display area, the user does not specify the correction area, and the LED display device performs power control with an average pixel value based on the image data of the entire video display area. When the average pixel value of the still image area is small, the average pixel value of the entire video display area also becomes small. Therefore, power saving control is not performed even if the average pixel value of the moving image area becomes large. On the other hand, by setting the correction area 22 as in the first embodiment, the LED display device can efficiently perform power saving control regardless of the average pixel value of the still image portion outside the correction area 22. Power saving control can be performed. In the first embodiment, the LED display device corrects the brightness of the image displayed in the correction area 22 for each frame, but the LED display device displays the brightness in the correction area 22 by the similar brightness correction control operation. The power may be controlled by correcting the dynamic range of the image to be displayed.

To summarize the above, the LED display device according to the first embodiment includes a video display area 21 in which images based on video signals are sequentially displayed for each frame, and a correction area 22 provided in a part of the video display area 21. The brightness correction control circuit 10 includes a display unit 20 including the display unit 20 and a brightness correction control circuit 10 that corrects the brightness of the image displayed in the correction area 22 for each frame. A brightness information calculation circuit 13 that calculates information, a correction coefficient calculation circuit 14 that calculates a brightness correction coefficient based on the brightness information, and a correction calculation circuit 17 that corrects a video signal displaying an image in the correction area 22 with the brightness correction coefficient. In addition, when displaying an image in the video display area 21, the display unit 20 displays in the correction area 22 an image based on the video signal corrected by the brightness correction control circuit 10 for each frame. With the above-described configuration, the LED display device can perform the power saving control in which the image quality deterioration due to the gradation reduction of the still image video is not noticeable. For the power saving control, the LED display device performs the brightness correction control of the correction area 22 in units of frames included in the video signal, so that even if the video is close to a still image such as a PC image, the image quality deteriorates after the correction. Is not noticeable.

Further, the correction coefficient calculation circuit 14 of the LED display device of the first embodiment makes the brightness correction of the image displayed in the correction area 22 after correction by the correction calculation circuit 17 smaller than the brightness of the image before correction. Calculate the coefficient. With the above-described configuration, the LED display device can reduce the brightness of the image displayed in the correction area 22 while suppressing the deterioration of the image quality of the video display area 21, and can save power.

Further, the correction coefficient calculation circuit 14 of the LED display device according to the first embodiment calculates the brightness correction coefficient according to the magnitude of the value of the brightness information such that the brightness correction coefficient decreases as the value of the brightness information increases. .. With the above-described configuration, the LED display device can correct the darkness by the correction calculation circuit 17 as the brightness of the image in the correction area 22 is brighter, and thus suppresses the image quality deterioration of the image displayed in the video display area 21. However, power can be saved.

Further, the correction coefficient calculation circuit 14 of the LED display device according to the first embodiment performs pre-correction so that each brightness information of each image based on the video signal corrected for each frame by the correction calculation circuit 17 becomes a predetermined value. The brightness correction coefficient is calculated according to the magnitude of the value of each brightness information. With the above-described configuration, the LED display device can correct the brightness to be darker by the correction calculation circuit 17 as the brightness of the image in the correction area 22 is brighter, while suppressing the image quality deterioration of the image displayed in the video display area 21. Power saving is possible. The LED display device can also reduce the maximum value of power consumption to a constant value.

Further, the brightness correction control circuit 10 of the LED display device according to the first embodiment corrects the brightness of the image displayed in the correction area 22 when the brightness information is equal to or higher than the predetermined threshold value. With the above configuration, the LED display device can reduce the brightness in the correction area 22 by an amount corresponding to the power over, when the brightness of the correction area 22 is too bright or the power consumption is equal to or higher than a predetermined value. As a result, the LED display device can suppress the peak power without the user feeling the decrease in the brightness of the entire image display area 21.

In addition, the brightness correction control circuit 10 of the LED display device according to the first embodiment displays the area setting unit 11 that sets the correction area 22 and the input video signal in the correction area 22 set by the area setting unit 11. And a first area determination circuit 12 for determining whether or not the image signal is a video signal of an image to be displayed. The brightness information calculation circuit 13 is configured to correct the correction area set by the area setting unit 11 based on the determination by the first area determination circuit 12. Luminance information is calculated from the video signal of the image displayed on 22. With the above configuration, the LED display device can correct the brightness of the moving image portion and perform power saving control while maintaining the image quality of the still image portion. Although only one correction area 22 is set in the first embodiment as shown in FIG. 2, the number of correction areas 22 is not necessarily one. The area setting unit 11 may specify a plurality of correction areas, and the LED display device may perform the above-described brightness correction operation on the plurality of correction areas. This increases the power saving effect of the LED display device.

In addition, the display unit 20 of the LED display device of the first embodiment is arranged in the video display area 21 and includes a plurality of pixels having a pixel value corresponding to the brightness of the image based on the video signal, and the brightness information. The brightness information calculated by the calculation circuit 13 is the average pixel value in the correction area 22, and the correction calculation circuit 17 corrects the pixel value of the pixel included in the correction area 22 with the brightness correction coefficient. With the above configuration, the LED display device can easily calculate the luminance information and the luminance correction coefficient using the pixel value without adding a device for measuring the luminance. Further, since the LED display device can accurately set the corrected pixel value for each pixel, it is possible to save power without degrading image quality. In the first embodiment, the brightness information calculation circuit 13 calculates the average pixel value corresponding to the average brightness in the correction area 22 as the brightness information. The total sum may be calculated as the brightness information. In that case, the display unit 20 of the LED display device is arranged in the video display area 21 and includes a plurality of pixels having a pixel value corresponding to the brightness of the image based on the video signal, and the brightness information calculation circuit 13 performs the calculation. The brightness information is the sum of the pixel values of the pixels included in the correction area 22, and the correction calculation circuit 17 corrects the pixel values of the pixels included in the correction area 22 with the brightness correction coefficient. Further, the brightness information calculation circuit 13 may calculate the sum of pixel values of the LEDs of each color included in each pixel. Even if the LED display device performs the brightness correction control operation by using the sum of the pixel values, the same effect as described above can be obtained.

Further, each pixel of the display unit 20 of the LED display device of the first embodiment is made up of a group of a plurality of LEDs having different emission colors, each LED has a pixel value, and the correction calculation circuit 17 is The duty ratio for lighting control is corrected based on the brightness correction coefficient. With the above configuration, even if the LED display device is a full-color display device that performs PWM control, it is possible to correct the brightness of the moving image portion and perform power saving control while maintaining the image quality of the still image portion. Is.

(Modification of Embodiment 1)
The modification of the first embodiment shows a modification of the brightness correction coefficient calculated by the correction coefficient calculation circuit 14. The brightness correction control circuit 10 does not necessarily have to perform the threshold value judgment of the brightness information, and in any case of taking the average pixel value, the brightness correction control circuit 10 corrects the video signal for displaying the image in the correction area 22. Good. In that case, step S6 is omitted in the flowchart of FIG. For example, in FIG. 6, the correction coefficient calculation circuit 14 assigns a brightness correction coefficient that gradually decreases from the average pixel value 0 to 255, and the correction calculation circuit 17 corrects the video signal by the brightness correction coefficient. Even with the LED display device having such a configuration, the brightness of the image in the correction area 22 can be reduced and the power consumption can be reduced.

Further, as another modification, the correction coefficient calculation circuit 14 assigns a constant brightness correction coefficient to the size of the average pixel value, and the correction calculation circuit 17 corrects the video signal with the brightness correction coefficient. Is also good. For example, the correction coefficient calculation circuit 14 may calculate a constant brightness correction coefficient 0.75 when the average pixel value is 192 or more. Even with such a configuration, the LED display device can save power.

Further, in the above-described first embodiment, the correction coefficient calculation circuit 14 sets the brightness correction coefficient so that each average pixel value of each image in the correction area 22 based on the video signal corrected by the correction calculation circuit 17 becomes 192. However, it is not always necessary to correct each average pixel value after correction to a constant value. For example, in FIG. 6, the correction coefficient calculation circuit 14 calculates the brightness correction coefficient 1 when the average pixel value 192, calculates the brightness correction coefficient 0.9 when the average pixel value 255, and interpolates the brightness correction coefficient between them. It may be calculated as follows. Even with such a configuration, the LED display device can save power.

<Second Embodiment>
The LED display device according to the second embodiment will be described. Note that the description of the same configuration and operation as those in the first embodiment will be omitted. The LED display device according to the first embodiment calculates the brightness correction coefficient based on the average pixel value of the image displayed in the correction area 22, and corrects the video signal using the brightness correction coefficient. The LED display device according to the second embodiment further has a function of correcting the video signal when the video displayed in the correction area 22 is determined to be a moving image.

FIG. 8 is a functional block diagram showing the configuration of the LED display device according to the second embodiment. The brightness correction control circuit 10 further includes a moving image determination unit, and in the second embodiment, the brightness correction control circuit 10 includes a moving image determination circuit 18 as the moving image determination unit. The moving image determination circuit 18 inputs each brightness information calculated by the brightness information calculation circuit 13 for each frame, and determines whether or not the difference between the brightness information is a predetermined difference or more. The moving image determination circuit 18 temporally observes the average pixel value of the correction area 22 calculated for each frame by the luminance information calculation circuit 13. For example, the moving image determination circuit 18 calculates the difference between the average pixel value AveRGB(t) at the frame timing t and the average pixel value AveRGB(t-1) at the immediately preceding frame timing (t-1). The moving image determination circuit 18 determines that a moving image is input as a video signal for displaying an image in the correction area 22 when the difference is equal to or larger than a predetermined difference, and when the difference is less than the predetermined difference, the still image is determined. Is determined to have been input. When the moving image determination circuit 18 determines that the image is a moving image, the correction coefficient calculation circuit 14 calculates the brightness correction coefficient and the correction calculation circuit 17 performs the brightness correction control in the same manner as in the first embodiment.

The moving image determination circuit 18 is, for example, a programmed processor or a parallel programmed processor, like the other circuits described in the first embodiment. Further, in the LED display device of the second embodiment, the function of the moving image determination circuit 18 may be realized by software as in the first embodiment. In that case, the function of determining whether or not the difference between the brightness information calculated for each frame is equal to or more than a predetermined difference is described in the program. Its pro gram is stored in the memory 19b of the processing circuit 19 is executed by the processor 19a.

The brightness correction control operation for power saving control of the LED display device according to the second embodiment will be described with reference to the block diagram of FIG. 8 and the flowcharts of FIGS. 9 and 10. The steps up to step S4 in which the luminance information calculation circuit 13 calculates the average pixel value are the same as in the first embodiment. In the second embodiment, the moving image determination circuit 18 determines whether the difference between the average pixel values calculated for each frame by the brightness information calculation circuit 13 is equal to or more than a predetermined difference (step S5). The predetermined difference is stored in advance in a memory or the like, for example, and is read by the moving image determination circuit 18 as needed. In the second embodiment, when the predetermined difference is D, and the average pixel value AveRGB(t) and the average pixel value AveRGB(t-1) satisfy the following Expression 3, the moving image determination circuit 18 It is determined that the image in the correction area 22 is a moving image.

If NO is determined in step S5, that is, if the image is not a moving image, the LED display device does not perform the brightness correction control operation, and thus the process proceeds to step S9. If YES is determined in step S5, that is, if the image is a moving image, the moving image determination circuit 18 outputs the average pixel value to the correction coefficient calculation circuit 14. The correction coefficient calculation circuit 14 determines whether or not the average pixel value is equal to or larger than a predetermined threshold value (step S6). The subsequent steps are the same as the brightness correction control operation performed by the LED display device described in the first embodiment.

(effect)
In summary, the brightness correction control circuit 10 of the LED display device according to the second embodiment determines whether the difference between the brightness information calculated by the brightness information calculation circuit 13 for each frame is equal to or more than a predetermined difference. The moving image determination circuit 18 is further provided, and when the moving image determination circuit 18 determines that the difference is equal to or more than a predetermined difference, the correction calculation circuit 17 corrects the video signal for displaying the image in the correction area 22. With the above configuration, the LED display device can perform power control by the above-described brightness correction control operation when the video displayed in the correction area 22 is determined to be a moving image. In the LED display device described in the first embodiment, the brightness correction control operation is performed when the average pixel value is large even if the image displayed in the correction area 22 is a still image. In such a case, the LED display device does not perform the brightness correction control operation because the moving image determination circuit 18 does not determine that it is a moving image. Therefore, the LED display device of the second embodiment can perform power control while maintaining the image quality of the still image portion.

The moving image determination circuit 18 of the LED display device according to the second embodiment determines the determination of a moving image or a still image at the average pixel value AveRGB(t) at the frame timing t and at the frame timing (t-1) immediately before that. Although the determination is made based on the difference between the average pixel value AveRGB(t−1) and the two frames, the moving image determination circuit 18 determines the determination of the moving image or the still image by comparing the average pixel values of three or more frames. May be. Also in that case, the LED display device has the same effect as that of the second embodiment.

The display device according to the first or second embodiment of the present invention has been described above by taking the LED display device in which the pixel of the display unit 20 is made up of a set of a plurality of LEDs as an example. However, the pixel has an OLED (Organic Light). Even in a display device including other light emitting elements such as an emitting diode, the display device has the same effect as that of the first or second embodiment.

It should be noted that, in the present invention, the respective embodiments can be freely combined, or the respective embodiments can be appropriately modified or omitted within the scope of the invention. Although the present invention has been described in detail, the above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that innumerable variants not illustrated can be envisaged without departing from the scope of the invention.

10 brightness correction control circuit, 11 area setting unit, 12 first area determination circuit, 13 brightness information calculation circuit, 14 correction coefficient calculation circuit, 15 frame memory, 16 second area determination circuit, 17 correction calculation circuit, 18 moving image determination circuit , 20 display area, 21 video display area, 22 correction area.

Claims (8)

A display unit including a video display area in which images based on the video signal are sequentially displayed for each frame, and a correction area provided in a part of the video display area,
A brightness correction control unit that corrects the brightness of the image displayed in the correction area for each frame,
The brightness correction control unit,
A brightness information calculation unit that calculates brightness information from the video signal for displaying an image in the correction area;
A correction coefficient calculator that calculates a brightness correction coefficient based on the brightness information;
A correction calculation unit that corrects the video signal for displaying an image in the correction area with the brightness correction coefficient;
And a moving image determination unit that determines whether or not the difference in the luminance information in each correction area calculated for each frame by the luminance information calculation unit is equal to or more than a predetermined difference,
The correction calculation unit corrects the video signal for displaying an image in the correction area when the moving image determination unit determines that the difference is equal to or more than the predetermined difference,
The display device displays an image based on the video signal corrected by the brightness correction control unit for each frame in the correction area when displaying an image in the video display area. The correction coefficient calculation unit calculates the brightness correction coefficient that makes the brightness of an image displayed in the correction area after correction by the correction calculation unit smaller than the brightness of an image based on a video signal before correction. Display device according to. The display device according to claim 2, wherein the correction coefficient calculation unit calculates the brightness correction coefficient according to the magnitude of the value of the brightness information such that the brightness correction coefficient decreases as the value of the brightness information increases. .. The correction coefficient calculation unit determines a value of each of the brightness information before correction so that each brightness information of each image based on the video signal corrected for each frame by the correction calculation unit has a predetermined value. The display device according to claim 3, wherein the brightness correction coefficient is calculated according to the following formula. The display device according to claim 1, wherein the brightness correction control unit corrects the brightness of an image displayed in the correction area when the brightness information is equal to or more than a predetermined threshold value. .. The brightness correction control unit,
An area setting unit for setting the correction area,
The input video signal further includes an area determination unit that determines whether or not the video signal of the image displayed in the correction area set by the area setting unit,
The brightness information calculation unit calculates the brightness information from the video signal of the image displayed in the correction area set by the area setting unit based on the determination of the area determination unit. The display device according to any one of claims. The display unit includes a plurality of pixels arranged in the video display area and having a pixel value corresponding to the brightness of an image based on the video signal,
The brightness information calculated by the brightness information calculation unit is a sum of the pixel values of the pixels included in the correction area or an average pixel value in the correction area,
The display device according to claim 1, wherein the correction calculation unit corrects the pixel value included in the pixel included in the correction area with the brightness correction coefficient. Each of the pixels of the display unit is composed of a set of a plurality of light emitting elements having different emission colors,
Each said light emitting element has each pixel value,
The display device according to claim 7, wherein the correction calculation unit corrects a duty ratio related to lighting control of the light emitting element based on the brightness correction coefficient.

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