KR102225161B1 - An apparatus and method to high quality image implementation technology for improving outdoor visibility of LED display Board - Google Patents

Abstract

The present invention relates to a high-quality image realization system for improving the outdoor visibility of an LED electronic display board, wherein a human eye perceives that the luminance of the LED electronic display board is low in daytime when daylight illuminance rises relative to a change in ambient brightness, that is, the daylight illuminance of the external environment. The present invention focuses on the fact that the luminance of the LED electronic display board is perceived as high at night when the daylight illuminance falls, and at night, the brightness, saturation, and gamma correction are adaptively processed to improve visibility by increasing a contrast ratio while lowering the brightness of images with bright grayscale values as well as dark grayscale values.

Description

An apparatus and method to high quality image implementation technology for improving outdoor visibility of LED display Board}

The present invention relates to a high-quality image realization system for improving the outdoor visibility of an LED sign, and more particularly, a main light control device using a dimming control device to adaptively respond to the luminance and gamma correction of the LED sign. In accordance with the change in degree, the brightness and contrast ratio are increased while processing the brightness of images with dark and bright gradation values during the day, and lowering the brightness of images with bright gradation values as well as dark gradations at night, while reducing the luminance and contrast ratio. It is possible to improve the visibility by increasing it. Also, it is possible to see high-quality images at all times by adaptively processing brightness, contrast, saturation, and gamma correction so that the information of the input image is transmitted without distortion to the output image information. It relates to a high-quality image realization system for improving visibility.

Conventional LED display boards use a digital image playback device such as a computer or DVD player to improve the quality of images such as brightness, contrast, saturation, and gamma correction. The standard of LPM (LED Pixel Module) module by transmitting control signals to the LED signboard and performing functions such as bit conversion, gamma correction, and dimming control by the brightness and color control device mounted on the LED signboard using these signals. It converts the video data and control signal to fit and transmits it to the LPM module to reproduce the video.

In addition, in a conventional LED display board, brightness, contrast, gamma correction, etc. built into a digital image reproducing apparatus are performed using Equation (1) in order to improve the quality of an image. Equation (1) is as follows.

f(x) = gain× X ^gamma ± offset equation (1)

gain=contrast control constant

offset=brightness adjustment constant

gamma = Gamma value adjustment constant

At this time, when the input red, green, and blue 8-bit digital image data value is X , the 8-bit digital image data is displayed in 256 steps with a gray scale of 0 to 255 in order to increase the brightness (luminance) of the LED billboard. If 30 is added as a brightness control constant to the 256-step grayscale, the grayscale value increases by 30 as shown in FIG. 1, so that the dark part becomes bright, but the grayscale value of the bright part, which is 225 or more, is saturated to 255. .

In order to reduce the brightness, if 30 is subtracted by the brightness control constant, as shown in Fig. 2, all grayscales from 0 to 30 become 0, 255 becomes 225, and all grayscales are lowered to the same level, and dark grayscales are reduced to 0. Become saturated.

In addition, in order to increase the contrast, when the contrast control constant is set to 1.3, since the contrast is a multiply function, there is no significant difference in dark gradations, but the response increases as the contrast increases as shown in FIG. 3, and increasing the contrast increases the contrast ratio, but the bright color part. Becomes saturated at

In order to reduce the contrast, when the contrast control constant is set to 0.8, as shown in FIG. 4, the response increases in the bright gradation and the image becomes dark as the ratio of darkening increases.

LED billboards installed outdoors have a luminance of 6,000~10,000Cd/㎡ or more during the day, and at night, according to the light emission allowance standard, keep below 1,500Cd/㎡ from 60 minutes to 24:00 after sunset, and 24:00~ Since it must be kept below 1,000Cd/m2 until 60 minutes before sunrise, the luminance change becomes very severe, and if the brightness and contrast described above are adjusted, there is a problem that high-quality images cannot be displayed.

Human vision responds nonlinearly to brightness according to Weber's law. For this reason, for example, if the brightness of light is displayed linearly within a bit depth limited to 8 bits for each of red, green, and blue, the brightness of a dark part where the human eye reacts sensitively is reduced. When it changes, it does not feel smooth, but a phenomenon that looks disconnected (posterization) occurs, so it is necessary to display non-linearly dark areas in more detail in order to show optimal image quality within the limits of a given amount of information expression.

Therefore, in order to improve the image quality by improving the edge sharpness of the image, the gamma correction value rather than the brightness and contrast is adjusted within the range of 2.0 to 2.5 and used.

Conventional LED display boards convert 8-bit digital image data for red, green, and blue transmitted from a digital image reproducing device into signals conforming to the standard of the LPM module and play them back on the screen, resulting in very low luminance and 8-bit image data. The image is reproduced by performing bit conversion from 12 bits to within 16 bits and correcting the gamma value to 2.0 or 2.5.

However, the luminance of the LED signboard is maintained above 10,000Cd/㎡ during the day and below 1,000Cd/㎡ at night, so the luminance change is very severe. The peripheral illumination of the LED display board is also about 80,000Lux or more during the day, and at night. It can be seen that the change in the daylight illuminance is very severe as it approaches 0Lux. As shown in FIG. 5, the human eye is relatively perceived according to the change in the daylight illuminance, so during the day when the daylight illuminance increases, the brightness of the LED signboard is 10,000. Even if it is Cd/m2 or more, it is perceived as low, and at night when the daylight illuminance is lowered, it is perceived as high even if the luminance is maintained at 1,000 Cd/m2 or less.

As such, outdoors with high daylight illuminance, the amount of light emitted from the LED display becomes relatively small, making it difficult to accurately recognize the image, and the display device composed of LCD, PDP, and OLED is not visible because the luminance is less than 1,000Cd/m². . Such a phenomenon causes a problem in that if the brightness of light reflected on the screen is brighter than the image displayed on the display, the image appears dark, making it difficult to recognize.

In addition, as UHD broadcasting is commercialized, the interest of those who want to receive realistic video services is not only limited to one-dimensional elements such as resolution expansion, but the resolution, number of bits, frame rate, and color gamut of video for high-definition implementation. , In order to improve the visibility of the outdoor LED signboards installed outdoors by reaching a complex factor that considers the brightness (dynamic range), the image is brightly processed while maintaining a high contrast ratio during the day according to the change of the surrounding daylight illumination, and a high contrast ratio is achieved at night. It is necessary to adjust the brightness and gamma correction values so that the brightness of the image is lowered while maintaining it so that the high-quality image can be displayed at all times. The conventional LED signboard uses a dimming control device to control the brightness. As described above, the image is saturated. There is a problem in reproducing a high-quality image because it is disconnected or disconnected, and the high contrast ratio cannot be maintained.

The preceding patent is divided into ITS and ATS within the MCU of the billboard, and through ATS automatic switching operation in both directions, gamma correction, automatic dimming, brightness value of the billboard, module defects of the billboard can be checked from a distance, and the image contrast ratio of night and day can be checked. A configuration is described to check the status of the electronic signboard at 2WAY high speed from a long distance, configured to enable automatic control, temperature control, and linkage control of electronic signage required for image display calibration.

However, since the prior patent automatically checks the state of the electronic signboard or adjusts only the contrast through dimming control, there is a problem that it cannot be prevented from improper color deterioration, and accordingly, there is a problem that the visibility of the LED signboard at night decreases.

Prior patent: Korean Patent Publication No. 10-2015644 (2019.08.22.)

The present invention focuses on the fact that the human eye perceives low luminance of the LED signboard during the daytime when the daylight illuminance increases relative to the change in the ambient brightness, that is, the daylight illuminance, which is an external environment, and is perceived as high at night when the daylight illuminance decreases. In order to improve the visibility of the outdoor by matching the brightness and contrast of the LED display to the change of the daylight illuminance, the image with dark and bright gradations during the day is processed brightly, increasing the contrast ratio, and not only the dark gradations at night, but also the bright gradation values. Implement high-quality images to improve the outdoor visibility of LED display boards that can always watch high-quality images by adaptively processing brightness, saturation, and gamma correction to improve visibility by increasing the contrast ratio while lowering the brightness of the image. Its purpose is to provide a system.

The present invention relates to an LED display comprising a computer, a digital video playback device such as a DVD player, a video signal distribution device, a brightness and color control device, and a screen combining LPM modules, wherein the screen to be displayed on the LED sign is converted into a digital video signal. And converts the digital video signal into a DVI/HDMI transmission signal, TMDS signal, and transmits it to the video signal distribution device. A digital image reproducing apparatus that performs an image schedule function such as determining a display order, and functions such as contrast, gamma correction, brightness, and saturation adjustment; A DVI/HDMI receiver receiving the DVI/HDMI transmission signal TMDS signal, a dimming controller, an image and dimming data processing device, a timing and video control signal generator, and converting the dimming data and image data into a DVI/HDMI signal TMDS signal. A digital video signal distribution device comprising a repeater for transmitting to a brightness and color control device of a plurality of LED display boards using a DVI, HDMI, UTP cable, or the like; A repeater capable of receiving TMDS signals, which are DVI/HDMI signals transmitted using cables such as DVI, HDMI, UTP, etc., and transmitting the signals to other brightness and color control devices connected to the next stage, and clock signals and video signals. Timing and LPM module signal generator for converting data signals, image control signals, and dimming data signals, R, G, B memory devices in one FPGA, and perform operations to convert 8-bit image data from 12 bits to 20 bits A color enhancement device that performs functions of brightness control, saturation enhancement, and gamma correction to improve image quality, and a bit conversion and color enhancement processing unit that generates a control signal to control these devices. Brightness and color control device and shift clock signal, output enable signal, strobe that meet the standard of the LPM module so that the 12-bit to 20-bit image data generated by performing the brightness increase, decrease, and color enhancement can be transmitted to the LPM module. It characterized in that it comprises a control signal, such as a signal, a scan line selection signal and the role of transmitting to the LPM module, and the control signal is synchronized with the control signal to generate and transmit R, G, B image data to be displayed and transmits.

The brightness and color control device automatically selects the gamma correction constant value and the luminance control constant using the dimming data value so as to respond to the change in the main light illuminance in the LED billboard, so that it is always irrespective of the surrounding main light illuminance and the brightness of the LED billboard. Input image data having a value of 0 to 255, which is 8 bits, to improve outdoor visibility by selecting one of several gamma correction values according to the dimming data and having a high contrast maintenance module that controls to maintain a high contrast ratio. As an exemplary embodiment, bit conversion is performed into 16 bits so that the brightness of the LED display board has a value of 10,000 Cd/m 2, and the gamma correction constant value of the gamma correction value is 1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25, 3.5, If the dimming data that generates the image data by dividing it into 3.75, etc. is composed of 3-bit 0~7 values, that is, 8 steps, and the dimming data value is 7, the daylight illuminance value is very high. If the dimming data value that appears dark is increased and the dimming data value of which the daylight illuminance is lower by one level is 6, the gamma value is selected as 2.0 to lower the brightness of the grayscale that appears dark by one step, and the daylight illuminance is gradually lowered and the dimming data value at night. When this is 0, if the gamma value is set to 3.5 to make the dark part darker, the image with dark and bright gradation values during the day is displayed so that outdoor visibility can be improved by matching the brightness and contrast of the LED display board described above to the change in the main light illuminance. Brightness, saturation, and gamma correction are adaptively processed to improve visibility by increasing the contrast ratio while processing the brightness of images with bright gradation values as well as dark gradations low at night. It is characterized by being able to watch video.

The brightness and color control device automatically selects the gamma correction constant value and the brightness control constant using dimming data by matching the brightness and contrast of the LED display board to the change in the main light illuminance. High-quality images can be viewed at all times by enhancing the contrast ratio while processing images with gradation values brightly, and by increasing the contrast ratio while lowering the brightness of images with bright gradations as well as dark gradations at night. It is characterized by that.

The present invention enhances the contrast ratio while brightly processing images having dark and bright grayscale values during the day so that outdoor visibility can be improved by matching the brightness and contrast of the LED signboard with the change of the main light illuminance, and at night, not only the dark grayscale but also the bright grayscale. By reducing the brightness of an image having a value and increasing the contrast ratio, the visibility can be improved, so that a high-quality image can be viewed at all times.

In addition, since the information of the input image is transmitted without distortion to the output image information, there is an effect of always displaying a high-quality image.

In addition, the gamma correction constant value and the luminance control constant are automatically selected using the dimming data value to respond to the change in the main light illuminance in the LED billboard, so that the high contrast ratio can always be maintained regardless of the surrounding daylight illuminance and the luminance of the LED billboard. There is an effect.

1 is a curve for explaining an increase in brightness (offset=30, gamma=1) in a conventional LED display.
2 is a curve for explaining a reduction in brightness (offset=-30, gamma=1) in a conventional LED display.
3 is a curve for explaining an increase in contrast (gain = 1.3, gamma = 1) in a conventional LED display.
4 is a curve for explaining the reduction in contrast (gain = 0.8, gamma = 1) in a conventional LED display.
5 is a curve for explaining perceived brightness prediction image data for a change in daylight illuminance.
6 is a block diagram schematically showing the configuration of an LED billboard according to an embodiment of the present invention.
7 is a block diagram schematically showing the configuration of a video signal divider according to an embodiment of the present invention.
8 is a block diagram schematically showing the configuration of a brightness and color control apparatus according to an embodiment of the present invention.
9 is a curve for explaining an output image data value (luminance 10,000 [Cd/m2]) with respect to an input image data value according to an embodiment of the present invention.
10 is a curve for explaining an output image data value (luminance 1,500 [Cd/m2]) with respect to an input image data value according to an embodiment of the present invention.
11 is a curve for explaining a method of improving outdoor visibility (luminance 10,000 [Cd/m2]) by changing a gamma correction value according to an embodiment of the present invention.
12 is a curve illustrating a relationship between brightness (luminance) and a gamma curve due to a change in ambient daylight illuminance according to an embodiment of the present invention.

The present invention is an LED display consisting of a computer, a digital video playback device 100 such as a DVD player, a video signal distribution device, a brightness and color control device 311, and a screen in which LPM modules are combined, which can be displayed on the LED display board. Converts the screen into a digital video signal, converts the digital video signal into a DVI/HDMI transmission signal, TMDS signal, and transmits it to the video signal distribution device, setting the screen size and position of the LED billboard, controlling the screen division, ON/Off, A digital image reproducing apparatus 100 for performing an image schedule function such as scheduling an operating time and determining a display order of an image, and a function such as contrast, gamma correction, brightness, and saturation control; A DVI/HDMI receiving unit 211, a dimming controller 220, an image and dimming data processing device 212, a timing and video control signal generator 214, and a dimming data and image receiving the TMDS signal, which is the DVI/HDMI transmission signal. A digital video signal comprising a repeater that converts data into a DVI/HDMI signal TMDS signal and transmits it to the brightness and color control device 300 of multiple LED billboards using DVI, HDMI, UTP cables, etc. Distribution device 200; A repeater capable of receiving the TMDS signal, which is a DVI/HDMI signal transmitted using a cable such as DVI, HDMI, UTP, etc., and transmitting the signal to another brightness and color control device 300 connected to the next stage, and clocking the signal A timing and LPM module signal generator 320 for converting signals, video data signals, video control signals, and dimming data signals, and R, G, B memory devices 312, and 8-bit video data to 12 bits in one FPGA A computing device 313 that performs an operation to convert from to 20 bits, a color enhancement device that performs functions of brightness control, saturation enhancement, and gamma correction to improve image quality, and a control signal to control these devices. The brightness and color control device 300 including the bit conversion and color enhancement processing unit 310 that generates and transmits the 12-bit to 20-bit image data generated by performing the brightness increase, decrease, and color enhancement to the LPM module. The role of generating control signals such as shift clock signals, output enable signals, strobe signals, scan line selection signals, etc. that meet the specifications of the LPM module and transmitting them to the LPM module, and the R, G, B to be displayed in synchronization with this control signal. It characterized in that it comprises an LED display control unit for generating and transmitting image data.

The brightness and color control device 311 automatically selects the gamma correction constant value and the luminance control constant using dimming data values so as to respond to the change in the main light illuminance in the LED billboard to adjust the surrounding daylight illuminance and the brightness of the LED billboard. It is equipped with a high-contrast maintenance module that controls to always maintain a high contrast ratio, and has a value of 0 to 255, which is 8 bits, to improve outdoor visibility by selecting one of several gamma correction values according to the dimming data. As an embodiment of the input image data, bit conversion is performed into 16 bits so that the brightness of the LED display board has a value of 10,000 Cd/m 2, and the gamma correction constant value of the gamma correction value is 1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25. , 3.5, 3.75, etc., if the dimming data that generates the image data is composed of 3 bits 0~7 values, that is, 8 steps, and the dimming data value is 7, the gamma value is 1.75 at this time if the daylight illuminance value is very high. Select to increase the luminance of dark gradations, and if the dimming data value of which the daylight illuminance is lower by one level is 6, the gamma value is set to 2.0 to lower the luminance of the dark gradations by one step. When the dimming data value is 0, if the gamma value is set to 3.5 to make the dark part darker, the brightness and contrast of the LED billboard described above are adjusted to the change in the daylight illuminance to improve the outdoor visibility. Brightness, saturation, and gamma correction are adaptively processed to improve the visibility by increasing the contrast ratio while processing the brightness of images with bright gradation values as well as dark gradations low at night. It is characterized by being able to watch high-quality images at all times.

The brightness and color control device 311 automatically selects the gamma correction constant value and the brightness control constant using dimming data in accordance with the change of the main light illuminance by matching the brightness and contrast of the LED display board to the dark during the day so that outdoor visibility can be improved. The contrast ratio is increased by processing images with gradation and bright gradation values brightly, and by increasing the contrast ratio while lowering the brightness of images with bright gradation values as well as dark gradations at night, high-quality images are always produced. It is characterized by being able to watch.

6 is a block diagram schematically showing the configuration of an LED billboard according to an embodiment of the present invention, a digital image reproducing apparatus 100 such as a computer and a DVD player, a video signal distribution apparatus, and a brightness and color control apparatus 311 ) And in the LED signboard consisting of a screen combining LPM modules, the screen to be displayed on the LED signboard is converted into a digital video signal, and the digital video signal is converted into a TMDS signal, which is a DVI/HDMI transmission signal, and a video signal distribution device. It transmits to and performs video schedule functions such as setting the screen size and position of the LED display board, screen division control, ON/OFF, scheduling of operating hours, and determining the display order of images, and functions such as contrast, gamma correction, brightness, and saturation control. A digital image reproducing apparatus 100; A DVI/HDMI receiving unit 211, a dimming controller 220, an image and dimming data processing device 212, a timing and video control signal generator 214, and a dimming data and image receiving the TMDS signal, which is the DVI/HDMI transmission signal. A digital video signal comprising a repeater that converts data into a DVI/HDMI signal TMDS signal and transmits it to the brightness and color control device 300 of multiple LED billboards using DVI, HDMI, UTP cables, etc. Distribution device 200; A repeater capable of receiving the TMDS signal, which is a DVI/HDMI signal transmitted using a cable such as DVI, HDMI, UTP, etc., and transmitting the signal to another brightness and color control device 300 connected to the next stage, and clocking the signal A timing and LPM module signal generator 320 for converting signals, video data signals, video control signals, and dimming data signals, and R, G, B memory devices 312, and 8-bit video data to 12 bits in one FPGA A computing device 313 that performs an operation to convert from to 20 bits, a color enhancement device that performs functions of brightness control, saturation enhancement, and gamma correction to improve image quality, and a control signal to control these devices. The brightness and color control device 300 including the bit conversion and color enhancement processing unit 310 that generates and transmits the 12-bit to 20-bit image data generated by performing the brightness increase, decrease, and color enhancement to the LPM module. The role of generating control signals such as shift clock signals, output enable signals, strobe signals, scan line selection signals, etc. that meet the specifications of the LPM module and transmitting them to the LPM module, and the R, G, B to be displayed in synchronization with this control signal. It includes an LED display control unit that generates and transmits image data.

At this time, the LED display board is composed of a digital image reproducing device 100, an image signal distribution device 200, a brightness and color control device 300, and an LED screen 400 in which an LPM module is combined, see Figs. 6 to 12. It will be described as follows.

The digital image reproducing device 100 is composed of digital image reproducing devices such as a computer and a DVD player 110, which converts a screen to be displayed on an LED billboard into a digital image signal, and converts the image signal to DVI/HDMI. It converts the signal into a TMDS signal and transmits it to the image signal distribution device 200.

The digital image reproducing apparatus 100 is mainly composed of a computer, and its roles include image scheduling functions such as setting the screen size and position of the LED billboard, controlling the screen division, ON/Off, scheduling operating hours, and determining the display order of images, and contrast. , Gamma correction, brightness, saturation control 120, etc. are performed.

As shown in FIG. 7, the video signal distribution device 200 includes a DVI/HDMI receiver 211, a dimming controller 230, an image and dimming data processing device 212, a timing and video control signal generator 214, and a DVI/HDMI. It is composed of a repeater (Repeater) 213 that can transmit signals to the brightness and color control device 300 of a plurality of LED display boards using DVI, HDMI, UTP, optical cables, and the like.

The DVI/HDMI receiver 211 receives the TMDS video signal, which is the DVI/HDMI signal transmitted from the digital video playback device 100, as a clock signal, video data (red, green, blue) signal, and video control (clock, horizontal synchronization, It converts into a vertical synchronization, data enable) signal and transmits it to the image and dimming data processing apparatus 212.

The dimming controller 230 generates dimming data using the daylight illuminance value input from the CdS optical sensor, and transmits the dimming data to the image and dimming data processing device 212. The image and dimming data processing apparatus 212 performs various operations that can improve image quality using dimming data values and image data signals to regenerate clock signals, image data signals, image control signals, and dimming data to be /Transmit to the HDMI repeater 213.

The timing and video control signal generator 214 generates clock signals and various control signals capable of operating the dimming controller 230 and the image and dimming data processing device 212 and provides them to respective devices. The DVI/HDMI repeater 213 converts the clock signal, video data signal, video control signal, and dimming data signal transmitted from the video and dimming data processing device 212 into TMDS signals, and converts these signals into multiple units using a transmission cable. It plays a role of simultaneously transmitting to the brightness and color control device 300 of the configured LED display board.

The brightness and color control device 300 of the LED display includes a DVI/HDMI repeater and a receiver 330, a bit conversion and color enhancement processing unit 310, a timing and LPM module signal generation unit 320, as shown in FIG. do.

The DVI/HDMI repeater and receiver 330 receives the TMDS signal transmitted from the video signal distribution device 200 using a transmission cable and transmits the signal to another brightness and color control device 300 connected to the next stage. It consists of a repeater and a receiving unit that converts the signal into a clock signal, an image data signal, an image control signal, and a dimming data signal to provide the bit conversion and color enhancement processing unit 310.

The bit conversion and color enhancement processing unit 310 includes an R, G, B memory device 312 in one FPGA, an operation device 313 that performs an operation to convert 8-bit image data from 12 bits to 20 bits, and an image A color enhancement device 315 that performs the functions of brightness control 316, saturation enhancement 317, and gamma correction 318 to improve the quality of the image, and a control device that generates a control signal to control these devices. (311) and the like.

The control device 311 uses a shift clock signal, a vertical synchronization signal, a horizontal synchronization signal, and a DE signal input from the DVI/HDMI receiving unit 330 to receive 8-bit image data of red, green, and blue digital video signals, respectively. Generates a memory address signal and a memory control signal that can be stored in the R, G, B memory device 312 or read out and transmitted to the computing device 313, and performs operations such as bit conversion and gamma correction. It generates an operation control signal capable of controlling the operation device 313 so as to be performed.

And, by using the dimming data, to generate a control signal capable of performing the functions of brightness control 316, saturation enhancement 317, and gamma correction 318, and control the timing and signal generator 320 of the LPM module. It plays a role of generating a control signal for.

The R, G, B memory device 312 can temporarily store each red, green, and blue 8-bit image data input from the DVI/HDMI receiver 330 in the R, G, B memory device 312. It is a memory device.

The memory is configured to store image data of even frames and image data of odd frames.

In such a storage method of the memory, when the image data of even frames output from the digital image reproducing apparatus 100 is stored, the image data of odd frames is transferred to the LPM module through the computing device 313 and the color enhancement device 315. Conversely, when the image data of odd frames is stored, the image data of even frames is transmitted to the LPM module through the computing device 313 and the color enhancement device 315.

Bit conversion arithmetic unit 313 for the luminance increase and decrease the first input red, green, and each 8-bit digital video data values of the blue color when said X is for luminance increase and decrease with respect to the digital image data value X is Equation (2) is performed to convert bits and improve outdoor visibility. Equation (2) is as follows.

수학식 (2)

Equation (2)

X = image data value

scale = bit control constant

gain = brightness control constant

gamma = Gamma correction constant

offset = overflow correction constant

As an embodiment, in the bit conversion and gamma correction operation using Equation (2), first, for gamma correction, the gamma correction constant value in the digital image data X is set within the range of 1.75 to 3.75 and the dimming data value transmitted from the image distribution device. By selecting one and performing an operation, the bit conversion is performed by multiplying the bit value adjustment constant in converting the luminosity bit into an image data value within 12 to 20 bits.

In addition, by using image data having a value of 0 to 255, which is 8 bits, the gamma correction constant value of 2.5 is selected according to the dimming data value so that the brightness of the LED signboard becomes 10,000 Cd/m 2, and converted into 16 bits of 0 to 65,535. To do this, first set the brightness control constant value to 1 using Equation (2).

And set the bit control constant value so that the f(x) value is greater than or close to 65,535, and scale× ^gamma If the value is greater than 65,535, the value exceeding the range of 16 bits is set as the overflow correction constant and subtraction is performed so that the f(x) value becomes 0~65,535. Data curves are shown. Here, the bit value of 65,535 becomes a bit value corresponding to the maximum luminance of 10,000Cd/m2 of the LED display.

In addition, as another embodiment, in order to reduce the brightness of the LED display board to 1,500Cd/m2 using Equation (2), the bit control constant and gamma correction constant values set by the above-described method are maintained as they are, and the brightness control constant value. Adjust the bit value to set the luminance control constant value so that the bit value is 0~9,830, that is, the luminance value 1,500Cd/㎡.In Fig. 10, the output image data curve with the luminance of the LED signboard is 1,500Cd/㎡ and a gamma correction constant value of 2.5. Shown.

Here, the bit value of 9,830 becomes a bit value corresponding to the luminance 1,500Cd/m2 of the LED display.

Even if the luminance value of 10,000 [Cd/m2] shown in FIG. 9 is reduced to 1,500 [Cd/m2], which is 15% or less, the output image data value corresponding to the input image data value is not saturated or cut off.

This means that the information of the input image is transmitted without distortion to the output image information because the value of the input image data has been increased from the minimum itself through bit conversion.

However, since a conventional LED signboard is implemented using Equation (1), input image data is saturated in a bright part or disappeared in a dark part as described above.

In the display device, the contrast ratio is a numerical value indicating how well the lightest color and the darkest color are expressed, and the level between complete black and complete white is measured and displayed. In other words, it can be seen as data on how many levels of shading can be displayed.

Basically, all images are divided into bright and dark areas. A display device with a high contrast ratio emphasizes the dark areas more strongly and shows the outline clearly. By clearly showing it, it is possible to express delicate colors.

The outdoor LED signboard has a luminance of 10,000 Cd/m2 or more during the day and a low display of 1,500 Cd/m2 or less at night, so that the luminance change is very large. In addition, since the human eye is relatively perceived by the change in the daylight illuminance, during the day when the daylight illuminance rises to about 80,000Lux or more, even if the brightness of the LED signboard is 10,000Cd/㎡, it is perceived as low, and the daylight illuminance falls close to about 0Lux At night, even if the luminance is 1,500Cd/m2, it is perceived as high. In order to improve the quality of the image to improve outdoor visibility, luminance control and gamma correction must be performed while maintaining a high contrast ratio in accordance with the daylight illuminance.

As described above, when the brightness and contrast ratio are increased or decreased in the conventional LED signboard, the image data value is saturated in the dark or bright area, and the information in this area disappears. Therefore, in the present invention, this problem is solved by implementing a brightness and color control device using Equation (2). However, even if the brightness and color control device is implemented using Equation (2), the display cannot be performed according to the perceived time of the human eye. In the present invention, in order to solve this problem, a dimming control device is attached to the image distribution device. The CdS optical sensor detects the daylight illuminance, generates dimming data, and transmits it to the brightness and color control device of the LED signboard, and the image information value does not disappear by this dimming data and automatically maintains a high contrast ratio while adjusting brightness and gamma correction. Invented a way to do it.

In order to cope with the change of daylight illuminance in this way, the gamma correction constant value and the brightness control constant in Equation (2) are automatically selected using the dimming data value, and always high contrast ratio regardless of the surrounding daylight illuminance and the luminance of the LED signboard. To be able to maintain,

As an embodiment, FIG. 11 shows bit conversion of input image data having a value of 0 to 255, which is 8 bits, to 16 bits so that the brightness of the LED signboard has a value of 10,000 Cd/m 2 using Equation (2), and gamma correction. The constant value is divided into 1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25, 3.5, 3.75, and the output image data for the input image is represented by a curve.

Here, the bit values of 65,535 are bit values corresponding to the maximum luminance of 10,000Cd/m2 of the LED display.

If the dimming data consists of 3 bits 0 to 7 values, that is, 8 steps, and if the dimming data value is 7, the daylight illuminance value is very high and it is said that the daylight illuminance value is very high, the gamma value is selected as 1.75 to increase the luminance of dark grayscale, If the dimming data value of which the daylight illuminance is lower by one level is 6, the gamma value is selected as 2.0 to lower the luminance of dark gray levels by one level.

And if the daylight illuminance gradually decreases and the dimming data value at night is 0, the gamma value is set to 3.5 to make the dark part darker. It is possible to display a high-quality image with improved visibility at all times by processing gradation images brightly and processing the luminance of dark gradation and bright gradation images to be low at night.

In addition, the brightness control of the LED signboard by the change in the main light illuminance is performed by using the dimming data value of 8 steps as described above, according to the brightness control constant value of Equation (2).

In other words, for example, when the dimming data value is 7, the luminance control constant value is set so that the output image data value F(x) is 65,535 so that the brightness of the LED signboard becomes 10,000Cd/m2, and the surrounding By selecting 1.75 or 2.0 according to the daylight illuminance of the human eye, the gamma correction constant is selected according to the visual perception of the human eye, and by setting the luminance and gamma adjustment constant values according to the change in the surrounding illuminance, the visibility is always improved according to the surrounding daylight illuminance. It is possible to display high-quality images.

In FIG. 12, as another example, when the dimming data value is 7, the luminance adjustment constant value is set so that the output image data F(x) is 65,535 so that the maximum luminance is 10,000 Cd/m2, and a gamma correction constant value of 1.75 is selected. .

And when the dimming data value is 6, the luminance control constant value was set to be 85% of the maximum luminance, and F(x) = 57,353, and the gamma correction constant value was selected as 2.0.

At this time, when the dimming data value is 5, 75% of the maximum luminance, the gamma correction constant value is 2.25, and when the dimming data value is 4, 62.5% of the maximum luminance, and the gamma correction constant value is 2.5.

As such, when the dimming data value is 3, 50% of the maximum luminance, the gamma correction constant value is 2.75, when the dimming data value is 2, 37.5% of the maximum luminance, the gamma correction constant value is 3.0, and the dimming data value is 1. When the luminance is 25%, the gamma correction constant is 3.25, the dimming data is 0, the maximum luminance is 15%, and the gamma correction constant is 3.5.

The timing and LPM module signal generation unit 320 is a bit conversion and color enhancement processing unit 310 to perform brightness increase, decrease, and color enhancement, so that the generated 12-bit to 20-bit image data can be transmitted to the LPM module. The shift clock signal, OUT enable (OE) signal, strobe (ST) signal, and scan line selection signal in accordance with the standard of the module are created and transmitted to the LPM module. B video data is created and transmitted.

The present invention made in this way is to increase the contrast ratio while brightly processing an image having a dark gradation and a bright gradation value in the daytime so that outdoor visibility can be improved by matching the brightness and contrast of the LED display board to the change in the main light illuminance. By increasing the contrast ratio while lowering the brightness of an image having a bright gray scale value as well as dark gray scales, it is possible to improve visibility, so that high-quality images can be viewed at all times.

In addition, since the information of the input image is transmitted without distortion to the output image information, there is an effect of always displaying a high-quality image.

In addition, the gamma correction constant value and the luminance control constant are automatically selected using the dimming data value to respond to the change in the main light illuminance in the LED billboard, so that the high contrast ratio can always be maintained regardless of the surrounding daylight illuminance and the luminance of the LED billboard. There is an effect.

High-quality video realization system to improve outdoor visibility of LED display boards

100: digital video playback device
110: computer, DVD player 120: brightness, contrast, saturation, gamma control
200: digital video signal distribution device
210: video signal distribution device
211: DVI/HDMI receiver 212: video and dimming data processing device
213: DVI/HDMI repeater 214: Timing and video control signal generator
220: dimming controller
300: Brightness and color control device
310: Bit conversion and color enhancement processing unit
311: control device 312: R, G, B memory device
313: calculating device 315: color enhancing device
316: brightness control 317: saturation improvement
318: Gamma correction
320: Timing and LPM module signal generator

Claims (3)

In the LED display consisting of a digital image reproducing apparatus 100 such as a computer, a DVD player, a video signal distribution apparatus, a brightness and color control apparatus 311, and a screen in which LPM modules are combined,
Converts the screen to be displayed on the LED signboard into a digital video signal, converts the digital video signal into a DVI/HDMI transmission signal, TMDS signal, and transmits it to the video signal distribution device, setting the screen size and position of the LED signboard, and controlling the screen division , ON/OFF, reservation of operating time, and a digital image reproducing apparatus 100 for performing functions such as image schedule functions such as determining the display order of images, and functions such as contrast, gamma correction, brightness, and saturation;
A DVI/HDMI receiving unit 211, a dimming controller 220, an image and dimming data processing device 212, a timing and video control signal generator 214, and a dimming data and image receiving the TMDS signal, which is the DVI/HDMI transmission signal. A digital video signal comprising a repeater that converts data into a DVI/HDMI signal TMDS signal and transmits it to the brightness and color control device 300 of multiple LED billboards using DVI, HDMI, UTP cables, etc. Distribution device 200;
A repeater capable of receiving the TMDS signal, which is a DVI/HDMI signal transmitted using a cable such as DVI, HDMI, UTP, etc., and transmitting the signal to another brightness and color control device 300 connected to the next stage, and clocking the signal Timing and LPM module signal generator 320 for converting signals, video data signals, video control signals, and dimming data signals, and R, G, B memory devices 312, and 8-bit video data to 12 bits in one FPGA A computing device 313 that performs an operation to convert from to 20 bits, a color enhancement device that performs functions of brightness control, saturation enhancement, and gamma correction to improve image quality, and a control signal to control these devices. Brightness and color control device 311 including a bit conversion and color enhancement processing unit 310 for generating
Shift clock signal, output enable signal, strobe signal, and scan line selection signal conforming to the standard of the LPM module so that the 12-bit to 20-bit image data generated by performing the brightness increase, decrease, and color enhancement can be transmitted to the LPM module. It includes an LED signboard controller that generates and transmits R, G, B image data to be displayed in synchronization with the role of creating and transmitting control signals such as, etc. to the LPM module,
The brightness and color control device 311 automatically selects the gamma correction constant value and the luminance control constant using dimming data values so as to respond to the change in the main light illuminance in the LED billboard to adjust the surrounding daylight illuminance and the brightness of the LED billboard. It is equipped with a high-contrast maintenance module that controls to maintain a high contrast ratio at all times, regardless of it.
As an example, for input image data having a value of 0 to 255, which is 8 bits, to improve outdoor visibility by selecting one of several gamma correction values according to the dimming data, the brightness of the LED display is 10,000 Cd/m². Convert bits to 16 bits to have
Dimming data generating image data by dividing the gamma correction constant value of the gamma correction value into 1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25, 3.5, 3.75, etc. If the dimming data value is 7 and the daylight illuminance value is very high, if the daylight is very high, the gamma value is set to 1.75 to increase the luminance of the dark grayscale. Select to lower the luminance of dark gradations by one level,
If the daylight illuminance is gradually lowered and the dimming data value at night is 0, the gamma value is set to 3.5 to make the dark part darker. Brightness, saturation, and contrast increase the contrast ratio while processing images with dark gradations and bright gradation values brightly, and lowering the brightness of images with bright gradation values as well as dark gradations at night. A high-quality image realization system for improving outdoor visibility of an LED signboard, characterized in that gamma correction is adaptively processed so that high-quality images can be viewed at all times.
delete The method of claim 1,
The brightness and color control device 311 automatically selects the gamma correction constant value and the brightness control constant using dimming data in accordance with the change of the main light illuminance by matching the brightness and contrast of the LED display board to the dark during the day so that outdoor visibility can be improved. The contrast ratio is increased by processing images with gradation and bright gradation values brightly, and by increasing the contrast ratio while lowering the brightness of images with bright gradation values as well as dark gradations at night, high-quality images are always produced. A high-quality video realization system for improving the outdoor visibility of an LED signboard, characterized in that it can be viewed.

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