JP2018010060A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of performing power saving control, so as to make the degradation of image quality of a still video inconspicuous.SOLUTION: The display device includes a display part which includes a video display area where an image based on a video signal is sequentially displayed for each frame and a correction area provided in a part of the video display area and a luminance correction control part which corrects the luminance of the image displayed on the correction area for each frame. The luminance correction control part includes a luminance information arithmetic part which arithmetically calculates luminance information from the video signal for displaying the image on the correction area, a correction coefficient arithmetic part which calculates a luminance correction coefficient on the basis of the luminance information, and a correction arithmetic part which corrects the video signal for displaying the image on the correction area by using the luminance correction coefficient. When displaying the image on the video display area, the display part displays the image based on the video signal corrected by the luminance correction control part for each frame on the correction area.SELECTED DRAWING: Figure 1

Description

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

  Display devices that use LEDs as pixels are often used for outdoor and indoor advertising displays and the like due to technological development of LED (Light Emitting Diode) and cost reduction. These LED display devices have been mainly used for displaying moving images such as natural images or animations. In recent years, with the narrowing of the pixel pitch, LED display devices are also used in displays for indoor use that have a short viewing distance, such as conference room displays and monitor video display displays. Among such indoor display devices, the LED display device for monitoring often displays a moving image on a part of the display area like a personal computer image and a still image on most of the other.

  Patent Document 1 discloses a display device that realizes power saving while suppressing an increase in power supply capacity. The display device described in Patent Document 1 predicts a current value flowing through the display panel based on an input video signal. When the sum of current values in units of frames is equal to or greater than a predetermined threshold, the display device corrects video signal processing, that is, image contrast and brightness, and the current value flowing through the display panel is 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 video displayed on the display panel is a moving image, image quality degradation due to correction is not noticeable, but a part of the moving image is a moving image and most of the image is a still image like a personal computer image. When a certain video is corrected, there is a problem that the gradation of the image is lowered depending on the degree of correction, and the image quality is noticeable.

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

  The display device according to the present invention displays a video display area in which an image based on a video signal is sequentially displayed for each frame, a display unit including a correction area provided in a part of the video display area, and the correction area. A luminance correction control unit that corrects the luminance of the image for each frame, and the luminance correction control unit calculates a luminance information from a video signal for displaying the image in the correction area, and a luminance information calculation unit based on the luminance information. A correction coefficient calculation unit that calculates a correction coefficient, and a correction calculation unit that corrects a video signal for displaying an image in the correction area with a luminance correction coefficient, and the display unit displays the image in the video display area for each frame. An image based on the video signal corrected by the luminance correction control unit is displayed in the correction area.

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

3 is a functional block diagram illustrating a configuration of an LED display device in Embodiment 1. FIG. FIG. 6 is a diagram showing a video display area and a correction area in the first embodiment. 2 is a diagram illustrating a configuration of a processing circuit according to Embodiment 1. FIG. 3 is a timing chart showing an example of PWM drive in the first embodiment. 3 is a flowchart showing a luminance correction control operation in the first embodiment. 6 is a diagram illustrating a relationship between a luminance correction coefficient and an average pixel value in the first embodiment. FIG. 6 is a schematic diagram showing the luminance of a frame and a correction area in the first embodiment. FIG. FIG. 6 is a functional block diagram illustrating a configuration of an LED display device in a second embodiment. 10 is a flowchart showing a luminance correction control operation in the second embodiment. 10 is a flowchart showing a luminance correction control operation in the second embodiment.

  Embodiments of a display device according to the present invention will be described. In Embodiment 1 and Embodiment 2 shown below, as an example of a display device according to the present invention, an LED display device that displays a video information by arranging a plurality of LEDs in a matrix and controlling each LED to blink. The embodiment will be described.

<Embodiment 1>
(Configuration of LED display device)
FIG. 1 is a functional block diagram showing an 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 extracts an input terminal 1 for inputting a video signal from the outside, an effective area necessary 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 luminance correction control circuit 10 that corrects the luminance of an image based on the video signal, a display unit 20 that displays an image or video, and a drive circuit that drives the display unit 20 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 red (R), green (G), It is composed of three blue (B) LEDs. The display unit 20 illustrated 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 the pixel value corresponds to the luminance gradation of the image based on the video signal. In the first embodiment, each LED constituting 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 includes 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 images based on the video signal are sequentially displayed for each frame in the video display area 21. The display unit 20 includes a correction area 22 provided in a part of the video display area 21. In the coordinates representing the position in the video display area 21 in FIG. 2, an 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 specified by the user. The user designates a desired area in the video display area 21 from the area input unit 4 provided in the LED display device.

  Next, a configuration for realizing a function in which the LED display device corrects the luminance or 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 luminance correction control circuit 10. The luminance correction control circuit 10 includes an area setting unit 11 that sets an area designated by the area input unit 4 as a correction area 22. The luminance 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. In the first embodiment, the luminance correction control circuit 10 includes a first area determination circuit 12 as one of the area determination units. The correction area 22 may be a predetermined area. In this case, the LED display device does not need to be provided with the area input unit 4 and the area setting unit 11. In this case, the first area determination circuit 12 reads position information of a predetermined correction area previously stored in a memory or the like and uses it for the determination operation.

  The luminance correction control circuit 10 also obtains luminance information from the video signal that displays an 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. A luminance information calculation unit is further included. In the first embodiment, the luminance correction control circuit 10 includes a luminance information calculation circuit 13 as the luminance information calculation unit. The luminance information calculated by the luminance 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. The luminance correction control circuit 10 further includes a correction coefficient calculation unit that calculates a luminance correction coefficient based on the luminance information output from the luminance information calculation circuit 13. In the first embodiment, the luminance correction control circuit 10 includes: A correction coefficient calculation circuit 14 is included as the correction coefficient calculation unit.

  The luminance 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 luminance 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 luminance correction control circuit 10 includes a second area determination circuit 16 as an area determination unit separately from the first area determination circuit 12. In addition, the luminance correction control circuit 10 uses the correction coefficient calculation circuit 14 to generate 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 corrects the luminance correction coefficient to be output. In the first embodiment, the luminance correction control circuit 10 includes a correction calculation circuit 17 as a correction calculation unit. For example, the correction arithmetic circuit 17 multiplies the luminance signal included in the video signal by a luminance correction coefficient. The luminance signal is, for example, each pixel value that each pixel included in the correction area 22 has. 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 luminance correction control circuit 10 in the correction area 22. To drive.

(Brightness correction controller)
The luminance correction control circuit 10 shown in FIG. 1 individually includes circuits for correcting a video signal for displaying an image in the correction area 22 using a luminance correction coefficient as described above. When each circuit is dedicated hardware, each circuit is, for example, a programmed processor or a parallel programmed processor. Further, the luminance correction control circuit 10 may be provided with dedicated hardware that integrates each circuit into one, thereby realizing each function of each circuit.

  Further, the LED display device may realize each function of each circuit included in the luminance correction control circuit 10 by software. In that case, the LED display device includes a processing circuit 19 as shown in FIG. 3A, and the processing circuit 19 includes, for example, a processor 19a and a memory 19b connected to each other as shown in FIG. 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 program stored in the memory 19b describes the following brightness correction control function. The processing circuit 19 sets the area designated by the area input unit 4 as the correction area 22. The processing circuit 19 receives the video signal output from the video signal processing circuit 2 and determines whether the video signal is for displaying an image in the correction area 22. Based on the determination result, the processing circuit 19 calculates luminance information from a video signal that displays an image in the correction area 22 among the video signals input from the video signal processing circuit 2. The processing circuit 19 calculates a luminance correction coefficient based on the calculated luminance information. The processing circuit 19 determines whether or not 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 luminance of a video signal for displaying an image in the correction area 22 among the video signals input from the frame memory 15 using the previously calculated luminance correction coefficient. The processing circuit 19 reads the program describing the brightness correction control function 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. In addition, the LED display device may realize part of each function and each operation included in the luminance correction control circuit 10 with dedicated hardware and part of them with software.

(Brightness control method by PWM)
A luminance adjustment method 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 luminance by driving the display unit 20 by a 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 that is a basic period of PWM. FIG. 4B shows an example in which the duty ratio of the current pulse width for energizing the LED by the drive circuit 3 is 100%, and the current pulse width is equal to or less than one frame period of the video signal. FIG. 4C shows an example in which the duty ratio of the current pulse width is 75%. The PWM drive in FIG. 4C has a smaller duty ratio than that in FIG. 4B, and the luminance becomes dark because the LED energization time in one frame is short. The LED display device adjusts the luminance of each LED by changing the duty ratio of the current pulse width in one frame. Further, the PWM driving in FIG. 4C has a shorter power consumption because the energization time to the LED is shorter than that in FIG. 4B. Thus, the magnitude of the PWM duty ratio is related to the luminance and the power consumption. Therefore, the smaller the luminance value of the video signal, the smaller the duty ratio and the lower the power consumption consumed by the LED. On the other hand, the higher the luminance value of the video signal, the larger the duty ratio and the consumption consumed by the LED. Electric power is increased. The power consumption at the time of PWM driving with a duty ratio of 75% shown in FIG. 4C is 75% of the power consumption at the time of PWM driving with a duty ratio of 100% shown in FIG.

(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 designates an area where 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 as 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 or not 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 a video display area 21 different from the correction area 22, the LED display device performs the brightness correction control described in the first embodiment. The operation proceeds to step S9 without performing the operation. 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 together with the video signal to the luminance information calculation circuit 13. Output.

  The luminance information calculation circuit 13 calculates the luminance 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 luminance information is an average pixel value per LED included in the correction area 22. Assuming that 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 expressed by Equation 1 Is calculated by In the first embodiment, the R, G, and B LEDs of the LED display device have 8-bit pixel values, that is, 256 pixel values. Therefore, the maximum value that the average pixel value can take is 255. The luminance information calculation circuit 13 outputs the calculated average pixel value to the correction coefficient calculation circuit 14 as luminance information.

  The correction coefficient calculation circuit 14 determines whether or not the average pixel value calculated by the luminance information calculation circuit 13 is greater than or equal to a predetermined threshold value (step S6). In the correction coefficient calculation circuit 14 according to the first embodiment, a threshold average pixel value 192 is set as a predetermined threshold.

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

  On the other hand, when the average pixel value is equal to or greater than the predetermined threshold value, that is, when YES in step S6, the correction coefficient calculation circuit 14 calculates and assigns the luminance correction coefficient (step S8). That is, in the first embodiment, the correction coefficient calculation circuit 14 calculates the luminance 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 luminance of the image displayed in the correction area 22 after correction by the correction calculation circuit 17. A luminance correction coefficient that is smaller than the luminance of the image based on the previous video signal is calculated. In luminance correction by the correction calculation circuit 17 to be described later, the luminance correction coefficient is multiplied by the video signal to correct the luminance. Therefore, the correction coefficient calculation circuit 14 calculates the luminance correction coefficient to be 1 or less.

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

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

  For example, if the luminance correction coefficient is Mul, Mul is calculated by Equation 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 synchronization signals of the video signal, and is read out at a timing requested by the drive circuit 3 one frame later. In the first embodiment, data is read out 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 or not 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 the value output by the area setting unit 11 in step S1. If the video signal is a video signal for displaying an image in a 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, so step S12 is performed. Migrate 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 together with the determination result to the correction arithmetic circuit 17. To do.

  Based on the determination result of the second area determination circuit 16, the correction calculation circuit 17 displays a video signal for displaying an image in the correction area 22 among the video signals output from the frame memory 15 and input via the second area determination circuit 16. Is corrected with the luminance 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 luminance correction coefficient calculated by the correction coefficient calculation circuit 14. In the first embodiment, the video signal multiplied by the luminance correction coefficient by the correction arithmetic circuit 17 is a luminance signal included in the video signal, or image data related to luminance for displaying an image. That is. As an example, in the first embodiment, the correction arithmetic circuit 17 multiplies each pixel value by a luminance correction coefficient.

  The correction calculation circuit 17 outputs a control signal for displaying a corrected image in the correction area 22 and an uncorrected image in the video display area 21 outside the correction area 22 to the drive circuit 3. The display unit 20 is driven based on the control signal. That is, the drive circuit 3 performs PWM control on 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. (Step S12).

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

(effect)
As described above, the LED display device monitors the video signal in the correction area 22 designated by the user. When the average pixel value in the correction area 22 is larger than a preset threshold value, the power consumption increases. It can be determined and controlled 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 luminance 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, if the correction area 22 of the three frames shown in the center is too bright or if the power consumption is greater than or equal to a predetermined value, the LED display device according to the first embodiment can reduce the brightness by the amount of power over. Thus, the LED display device can suppress the peak power without causing the user to feel a decrease in brightness, and the power saving effect is greater than that in the conventional case in an operation application in which the operation time is long for one day.

  When operating an LED display device for monitoring purposes, most of the displayed video is a still image, and a moving image is often displayed on 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 luminance of the entire video display area based on the average pixel value of the video signal for displaying the image in the entire video display area. In this case, the power consumption of the LED display device can be reduced. However, when the dynamic range is narrowed, the luminance output gradation of the video display area is crushed, and a visual problem arises 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 is changed instantaneously or the dynamic range is narrowed, the problem is hardly recognized. For this reason, the user designates in advance the area for displaying the moving image as the correction area 22, and the LED display device performs power control by the brightness correction control operation in the designated correction area 22. It is possible to perform power control while maintaining the video quality.

  Further, when a moving image is displayed on a part of a still image in the video display area, the user does not specify a correction area, and the LED display device performs power control with an average pixel value based on 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 is also small. Therefore, power saving control is not performed even if the average pixel value in the moving image area increases. 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 luminance of the image displayed in the correction area 22 for each frame. However, the LED display device displays the image in the correction area 22 by the same luminance correction control operation. The dynamic range of the image to be corrected may be corrected to perform power control.

  In summary, 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. And a luminance correction control circuit 10 that corrects the luminance of the image displayed in the correction area 22 for each frame. The luminance correction control circuit 10 determines luminance from a video signal that displays an image in the correction area 22. A luminance information calculation circuit 13 for calculating information, a correction coefficient calculation circuit 14 for calculating a luminance correction coefficient based on the luminance information, and a correction calculation circuit 17 for correcting a video signal for displaying an image in the correction area 22 with the luminance correction coefficient. When the image is displayed in the video display area 21, the display unit 20 is based on the video signal corrected by the luminance correction control circuit 10 for each frame. To display the Ku image in the correction area 22. With the configuration as described above, the LED display device can perform power saving control such that image quality deterioration due to a decrease in gradation of a still image is not noticeable. For power saving control, the LED display device performs brightness correction control of the correction area 22 in units of frames included in the video signal. Therefore, even if the image is close to a still image such as a personal computer image, the image quality is deteriorated after correction. Is inconspicuous.

  Further, the correction coefficient calculation circuit 14 of the LED display device according to the first embodiment corrects the luminance of the image displayed in the correction area 22 after correction by the correction calculation circuit 17 to be lower than the luminance of the image before correction. Calculate the coefficient. With the configuration as described above, the LED display device can darken the luminance 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 luminance correction coefficient according to the value of the luminance information so that the luminance correction coefficient decreases as the luminance information value increases. . With the configuration as described above, the LED display device can correct the brightness to be darker by the correction arithmetic circuit 17 as the brightness of the image in the correction area 22 becomes brighter, and thus suppress deterioration in the image quality of the image displayed in the video display area 21. However, power saving is possible.

  Further, the correction coefficient calculation circuit 14 of the LED display device according to the first embodiment is configured so that the luminance information of each image based on the video signal corrected for each frame by the correction calculation circuit 17 has a predetermined value. A luminance correction coefficient is calculated according to the magnitude of each luminance information value. With the configuration as described above, the LED display device can correct the brightness to be darker by the correction arithmetic circuit 17 as the brightness of the image in the correction area 22 becomes brighter, while suppressing deterioration in the image quality 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 luminance correction control circuit 10 of the LED display device according to the first embodiment corrects the luminance of the image displayed in the correction area 22 when the luminance information is greater than or equal to a predetermined threshold value. With the configuration described above, the LED display device can reduce the brightness in the correction area 22 by the amount of power over when the brightness of the correction area 22 is too bright or when the power consumption is a predetermined value or more. As a result, the LED display device can suppress peak power without causing the user to feel a decrease in brightness of the entire video display area 21.

  Further, the luminance correction control circuit 10 of the LED display device according to the first embodiment displays the area setting unit 11 for setting 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 the image signal is an image signal to be processed. The luminance information calculation circuit 13 is a 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 perform power saving control by correcting the luminance of the moving image portion while maintaining the video quality of the still image portion. In the first embodiment, only one correction area 22 is set as shown in FIG. 2, but it is not always necessary to have one correction area 22. The area setting unit 11 may designate a plurality of correction areas, and the LED display device may perform the above-described luminance correction operation on the plurality of correction areas. Thereby, the power saving effect of the LED display device is increased.

  The display unit 20 of the LED display device according to the first embodiment includes a plurality of pixels that are arranged in the video display area 21 and have pixel values corresponding to the luminance of the image based on the video signal. The luminance information calculated by the arithmetic circuit 13 is an average pixel value in the correction area 22, and the correction arithmetic circuit 17 corrects the pixel value included in the pixels included in the correction area 22 with the luminance 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 the image quality. In the first embodiment, the luminance information calculation circuit 13 calculates the average pixel value corresponding to the average luminance in the correction area 22 as the luminance information, but the pixel value of the pixel in the correction area 22 The sum may be calculated as luminance 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 pixel values corresponding to the luminance of the image based on the video signal. The luminance information to be performed is the sum of the pixel values included in the pixels included in the correction area 22, and the correction calculation circuit 17 corrects the pixel values included in the pixels included in the correction area 22 with the luminance correction coefficient. In addition, the luminance information calculation circuit 13 may calculate the sum of the pixel values of the LEDs of each color that each pixel has. Even if the LED display device performs the brightness correction control operation using the sum of the pixel values, the same effect as described above is obtained.

  In addition, each pixel of the display unit 20 of the LED display device according to the first embodiment includes a group of a plurality of LEDs having different emission colors, each LED has a pixel value, and the correction arithmetic circuit 17 The duty ratio related to the lighting control is corrected based on the luminance 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 perform power-saving control by correcting the luminance of the moving image portion while maintaining the video quality of the still image portion. It is.

(Modification of Embodiment 1)
The modification of the first embodiment shows a modification of the luminance correction coefficient calculated and calculated by the correction coefficient calculation circuit 14. The luminance correction control circuit 10 does not necessarily have to perform threshold determination of luminance information. Even when taking any average pixel value, luminance correction control for correcting a video signal for displaying an image in the correction area 22 may be performed. 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 luminance correction coefficient that gradually decreases from the average pixel value 0 to 255, and the correction calculation circuit 17 corrects the video signal using the luminance correction coefficient. Even in 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.

  As another modification, the correction coefficient calculation circuit 14 assigns a fixed luminance correction coefficient to the average pixel value, and the correction calculation circuit 17 corrects the video signal by using the luminance correction coefficient. Also good. For example, the correction coefficient calculation circuit 14 may calculate a constant luminance 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.

  In the first embodiment, the correction coefficient calculation circuit 14 has the luminance correction coefficient so that the average pixel value of each image in the correction area 22 based on the video signal corrected by the correction calculation circuit 17 is 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 luminance correction coefficient 1 when the average pixel value is 192, calculates the luminance correction coefficient 0.9 when the average pixel value is 255, and interpolates the luminance correction coefficient therebetween. It may be calculated as follows. Even with such a configuration, the LED display device can save power.

<Embodiment 2>
The LED display device according to the second embodiment will be described. Note that the description of the same configuration and operation as in the first embodiment will be omitted. The LED display device according to the first embodiment calculates the luminance correction coefficient based on the average pixel value of the image displayed in the correction area 22, and corrects the video signal using the luminance 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 luminance correction control circuit 10 further includes a moving image determination unit. In the second embodiment, the luminance 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 piece of luminance information calculated for each frame by the luminance information calculation circuit 13 and determines whether or not the difference between the pieces of luminance information is equal to or greater than a predetermined difference. 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 previous 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 greater than or equal to a predetermined difference, and when the difference is less than the predetermined difference, Is determined to be input. When the moving image determination circuit 18 determines that the image is a moving image, the correction coefficient calculation circuit 14 calculates a luminance correction coefficient and the correction calculation circuit 17 performs luminance 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, similarly to the other circuits shown in the first embodiment. Further, in the LED display device according to the second embodiment, the function of the moving image determination circuit 18 may be realized by software as in the first embodiment. In this case, a function for determining whether or not the difference between the luminance information calculated for each frame is equal to or greater than a predetermined difference is described in the program. The program is stored in the memory 19b of the processing circuit 19 and 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 or not the difference between the average pixel values calculated for each frame by the luminance information calculation circuit 13 is greater than or equal to a predetermined difference (step S5). For example, the predetermined difference is stored in advance in a memory or the like, and is read by the moving image determination circuit 18 as necessary. 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 video in the correction area 22 is a moving image.

  If it is determined NO in step S5, that is, if it is determined that the video 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 S <b> 5, that is, if it is determined that the video 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 greater than or equal to a predetermined threshold value (step S6). The subsequent steps are the same as the luminance correction control operation performed by the LED display device described in the first embodiment.

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

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

  As described above, the display device according to the first or second embodiment of the present invention has been described by taking the LED display device in which the pixel of the display unit 20 is composed of a plurality of LEDs as an example, but the pixel is an OLED (Organic Light). Even in the case of a display device including other light emitting elements such as Emitting Diode), the display device has the same effects as those of the first embodiment or the second embodiment.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted. 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 countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 Brightness correction control circuit, 11 Area setting part, 12 1st area determination circuit, 13 Luminance information calculation circuit, 14 Correction coefficient calculation circuit, 15 Frame memory, 16 2nd area determination circuit, 17 Correction calculation circuit, 18 Movie determination circuit , 20 Display section, 21 Video display area, 22 Correction area.

Claims (9)

A display unit including a video display area in which an image based on the video signal is sequentially displayed for each frame, and a correction area provided in a part of the video display area;
A luminance correction control unit that corrects the luminance of the image displayed in the correction area for each frame;
The brightness correction control unit
A luminance information calculation unit for calculating luminance information from the video signal for displaying an image in the correction area;
A correction coefficient calculator that calculates a luminance correction coefficient based on the luminance information;
A correction calculation unit that corrects the video signal for displaying an image in the correction area with the luminance correction coefficient,
The display device, when displaying an image in the video display area, displays an image based on the video signal corrected by the luminance correction control unit for each frame in the correction area.   The correction coefficient calculation unit calculates the luminance correction coefficient that makes the luminance of an image displayed in the correction area after correction by the correction calculation unit smaller than the luminance of an image based on a video signal before correction. The display device described in 1.   The display device according to claim 2, wherein the correction coefficient calculation unit calculates the luminance correction coefficient in accordance with a value of the luminance information so that the luminance correction coefficient becomes smaller as the value of the luminance information becomes larger. .   The correction coefficient calculation unit is responsive to the magnitude of each luminance information value before correction so that each luminance 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 luminance correction coefficient is calculated.   The display device according to claim 1, wherein the luminance correction control unit corrects the luminance of an image displayed in the correction area when the luminance information is equal to or greater than a predetermined threshold. . The brightness correction control unit
An area setting unit for setting the correction area;
An area determination unit that determines whether the video signal to be input is the video signal of an image to be displayed in the correction area set by the area setting unit;
6. The luminance information calculating unit calculates the luminance information from the video signal of an image displayed in the correction area set by the area setting unit based on the determination of the area determining unit. The display device according to any one of the above. The luminance correction control unit further includes a video determination unit that determines whether or not a difference between the luminance information calculated for each frame by the luminance information calculation unit is equal to or greater than a predetermined difference.
The said correction calculating part correct | amends the said video signal which displays an image in the said correction area, when the said moving image determination part determines with it being more than a predetermined difference. The display device described in 1. The display unit includes a plurality of pixels that are arranged in the video display area and have pixel values corresponding to luminance of an image based on the video signal,
The luminance information calculated by the luminance 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 of the pixel included in the correction area with the luminance correction coefficient. Each pixel of the display unit is composed of a set of a plurality of light emitting elements having different emission colors,
Each light emitting element has a respective pixel value;
The display device according to claim 8, wherein the correction calculation unit corrects a duty ratio related to lighting control of the light emitting element based on the luminance correction coefficient.

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