WO2021005811A1

WO2021005811A1 - Led display device and brightness correction method

Info

Publication number: WO2021005811A1
Application number: PCT/JP2019/047018
Authority: WO
Inventors: 浅村　吉範; 清史澤田
Original assignee: 三菱電機株式会社
Priority date: 2019-07-08
Filing date: 2019-12-02
Publication date: 2021-01-14
Also published as: WO2021005672A1

Abstract

In the present invention, in situations where the operation period of an LED display device becomes lengthy and the brightness of multiple LEDs has declined, high-precision brightness correction is performed for maintaining evenness in the brightness and/or the color of an LED display unit so as to prevent the brightness of the LED display unit from dropping excessively, in accordance with the brightness of an LED which has deteriorated considerably due to a significantly long cumulative illumination time. The illumination time of each LED is integrated to calculate a cumulative illumination time each LED. A brightness deterioration rate for each LED is detected according to the cumulative illumination time, and a relationship between the illumination time of the LED and the brightness deterioration rate of the LED. From the brightness deterioration rates for the plurality of LEDs, a brightness deterioration rate at or below a threshold is selected. In accordance with the brightness deterioration rate at or below the threshold, a brightness correction coefficient is computed. Using the brightness correction coefficient, brightness correction is performed on a video signal. The plurality of LEDs are driven in accordance with the video signal on which the brightness correction has been performed.

Description

LED display device and brightness correction method

The present invention relates to an LED display device and a luminance correction method.

The light emitting diode (LED: Light Emitting Diode) display device includes an LED display unit including a plurality of LEDs. With the technological development and cost reduction of LEDs, LED display devices have come to be widely used for displaying advertisements indoors and outdoors.

LED display devices were once mainly used to display moving images such as natural images and animations. However, recently, since the pixel pitch of the LED display device has become narrower and the viewing distance of the LED display device has become shorter, the LED display device has been used to display a conference image, a surveillance image, etc. indoors. Is becoming. Further, when the LED display device displays a surveillance image, the LED display device often displays an image close to a still image input from a personal computer or the like.

The brightness of the LED decreases as the cumulative lighting time of the LED increases. Further, depending on the content of the image displayed on the LED display device, the cumulative lighting time of the plurality of LEDs provided in the LED display device becomes non-uniform. Therefore, depending on the content of the image displayed on the LED display device, the brightness reduction rate of the plurality of LEDs provided in the LED display device becomes non-uniform. As a result, as the operating time of the LED display device becomes longer, the brightness and color of the LED display unit become non-uniform. Therefore, a technique for solving this problem has been proposed.

For example, in the LED display device described in Patent Document 1, the cumulative lighting time of each LED element is calculated (paragraph 0016). Further, when the calculated cumulative lighting time of any LED element reaches a predetermined value, the brightness correction coefficient of the LED element is corrected (paragraph 0019). Further, the luminance correction is applied to the dot pattern data according to the corrected luminance correction coefficient (paragraph 0019). Further, the corrected display data to which the luminance correction has been performed is output to the LED display unit (paragraph 0019). Thereby, it is possible to suppress the brightness unevenness that may occur due to the difference in the cumulative lighting time of the LED elements (paragraph 0020).

In the LED display device described in Patent Document 2, it is determined whether or not the preset cumulative lighting time has reached the LED (paragraph 0024). When the cumulative lighting time has arrived, the brightness reduction rate is calculated with reference to the cumulative lighting time (paragraph 0024). Further, the duty ratio of the drive signal is increased by the calculated luminance reduction rate (paragraph 0026). This makes it possible to reduce the variation in the brightness of each LED (paragraph 0027).

Japanese Unexamined Patent Publication No. 11-15437 Japanese Unexamined Patent Publication No. 2006-330158

In the conventional LED display device, the brightness reduction rate of each LED is detected from the cumulative lighting time of each LED, and the brightness of a plurality of LEDs is corrected based on the detected brightness reduction rate. As a result, even when the brightness of each LED is reduced, the brightness and color of the image displayed on the LED display unit can be maintained uniformly.

However, the cumulative lighting time of a plurality of LEDs is not uniform, and a still image may be displayed on the LED display unit for a long period of time, and the plurality of LEDs may include an LED having a significantly long cumulative lighting time and a significantly reduced brightness. Then, in the conventional LED display device, when the plurality of LEDs include LEDs whose brightness is greatly reduced, the brightness of the remaining LEDs is reduced in accordance with the brightness of the LEDs whose brightness is greatly reduced, and the LED display unit The brightness drops excessively.

The present invention has been made in view of these problems. The problem to be solved by the present invention is to correct the brightness for maintaining the brightness and / or color uniformity of the LED display unit when the operating time of the LED display device becomes long and the brightness of a plurality of LEDs decreases. By providing an LED display device that can be performed with high accuracy and can suppress an excessive decrease in the brightness of the LED display unit in accordance with the brightness of the LED whose cumulative lighting time is extremely long and the brightness is greatly reduced. is there.

The present invention is directed to LED display devices.

The LED display device includes an LED display unit, an integration unit, a brightness reduction rate detection unit, a correction coefficient calculation unit, and a brightness correction unit.

The LED display unit includes a plurality of LEDs.

The integrating unit calculates the cumulative lighting time of each LED by performing the integration processing of the lighting time of each LED included in the plurality of LEDs.

The brightness reduction rate storage unit stores the relationship between the lighting time of the LED and the brightness reduction rate of the LED.

The brightness reduction rate detection unit detects the brightness reduction rate of each LED from the cumulative lighting time and the above-mentioned relationship to obtain the brightness reduction rate of a plurality of LEDs, and obtains the brightness reduction rate below the threshold value from the brightness reduction rate of the plurality of LEDs. select.

The correction coefficient calculation unit calculates the brightness correction coefficient based on the brightness reduction rate below the threshold value.

The brightness correction unit performs brightness correction on the video signal using the brightness correction coefficient and generates a video signal with the brightness correction performed.

The drive unit drives a plurality of LEDs according to the video signal for which the brightness has been corrected.

The present invention is also directed to a luminance correction method.

According to the present invention, the brightness correction coefficient used for the brightness correction is calculated according to the brightness reduction rate of the plurality of LEDs. Therefore, when the operating time of the LED display device becomes long and the brightness of a plurality of LEDs decreases, the brightness correction for maintaining the brightness and / or color uniformity of the LED display unit can be performed with high accuracy. ..

Further, according to the present invention, the brightness correction factor larger than the threshold value included in the brightness reduction rate of the plurality of LEDs is not reflected in the correction coefficient used for the brightness correction. Therefore, it is possible to prevent the brightness of the LED display unit from becoming excessively low in accordance with the brightness of the LED whose cumulative lighting time is extremely long and the brightness is greatly reduced.

The objectives, features, aspects, and advantages of the present invention will be made clearer by the following detailed description and accompanying drawings.

It is an internal block diagram which illustrates the LED display device of Embodiment 1-4. It is a timing chart for explaining the PWM drive performed in the LED display device of Embodiment 1-4. It is a graph which shows the relationship between the lighting time of the LED of R, G and B and the brightness decrease rate of the LED of R, G and B in the LED display device of Embodiment 1-4. It is a flowchart which shows the luminance correction method in the LED display device of Embodiment 1-2. It is a flowchart which shows the luminance correction method in the LED display device of Embodiment 3. It is a flowchart which shows the luminance correction method in the LED display device of Embodiment 4.

1 Embodiment 1
1.1 Display of an image by an LED display device FIG. 1 is an internal block diagram illustrating a light emitting diode (LED: Light Emitting Diode) display device according to the first embodiment.

The LED display device 1 of the first embodiment illustrated in FIG. 1 includes an input terminal 11, a video signal processing circuit 12, a luminance correction unit 13, a drive unit 14, and an LED display unit 15. The LED display unit 15 includes a plurality of LEDs 101. The plurality of LEDs 101 are arranged in a matrix. FIG. 1 illustrates a case where the plurality of LEDs 101 are 4 LEDs in the horizontal direction × 4 LEDs in the vertical direction = 16 LEDs. Each LED 102 included in the plurality of LEDs 101 includes a red (R) LED 102r, a green (G) LED 102g, and a blue (B) LED 102b.

A video signal is input to the input terminal 11 from an external device such as a personal computer.

The video signal processing circuit 12 processes the input video signal and outputs the processed video signal. The processing performed by the video signal processing circuit 12 includes video signal processing, selection processing, and the like. Video signal processing includes gamma correction and the like. The selection process includes a process of selecting a portion necessary for displaying an image by the LED display device 1 from the input video signal.

The brightness correction unit 13 performs brightness correction on the processed video signal using the brightness correction coefficient, and outputs the video signal for which the brightness correction has been performed.

The drive unit 14 drives a plurality of LEDs 101 according to the video signal whose brightness has been corrected.

As a result, the blinking and brightness of the plurality of LEDs 101 are controlled according to the video signal for which the brightness has been corrected. As a result, the LED display unit 15 displays an image corresponding to the image signal for which the brightness has been corrected. The displayed image includes characters, figures, images, and the like.

1.2 Brightness correction in the LED display device As shown in FIG. 1, the LED display device 1 includes an integrating unit 16, a lighting time storage unit 17, a brightness reduction rate storage unit 18, a brightness reduction rate detection unit 19, and a correction coefficient. The arithmetic unit 20 is provided.

The integration unit 16 calculates the cumulative lighting time of each LED 102 by performing an integration process of the lighting time of each LED 102.

The lighting time storage unit 17 stores the calculated cumulative lighting time of each LED 102.

The brightness reduction rate storage unit 18 stores the relationship between the lighting time of an LED having the same brightness reduction characteristic as the brightness reduction characteristic of the plurality of LEDs 101 and the brightness reduction rate of the LED. The LED is an LED of the same type as the plurality of LED 101 types. The relationship between the stored lighting time and the brightness reduction rate is represented by a table.

The brightness reduction rate detection unit 19 determines the brightness of each LED 102 based on the cumulative lighting time of each LED 102 stored in the lighting time storage unit 17 and the relationship between the lighting time stored in the brightness reduction rate storage unit 18 and the brightness reduction rate. The reduction rate is detected to obtain the brightness reduction rate of the plurality of LEDs 101. Further, the brightness reduction rate detection unit 19 selects a brightness reduction rate below the threshold value from the brightness reduction rates of the plurality of LEDs 101.

The correction coefficient calculation unit 20 calculates the brightness correction coefficient based on the brightness reduction rate below the selected threshold value. The correction coefficient calculation unit 20 calculates the brightness correction coefficient based on the maximum brightness reduction rate included in the brightness reduction rate below the selected threshold value. The calculated luminance correction coefficient is used when the luminance correction unit 13 performs the luminance correction.

According to this brightness correction, the brightness correction coefficient used for the brightness correction is calculated according to the brightness reduction rate of the plurality of LEDs 101. Therefore, when the operating time of the LED display device 1 becomes long and the brightness of the plurality of LEDs 101 decreases, the brightness correction for maintaining the brightness and color uniformity of the LED display unit 15 can be performed with high accuracy. ..

Further, according to this luminance correction, the luminance correction factor larger than the threshold value included in the luminance reduction rates of the plurality of LEDs 101 is not reflected in the luminance correction coefficient used for the luminance correction. Therefore, it is possible to prevent the brightness of the LED display unit 15 from becoming excessively low in accordance with the brightness of the LED whose cumulative lighting time is extremely long and the brightness is greatly reduced.

1.3 Acquisition of Relationship between Lighting Time and Brightness Decrease Rate The LED display device 1 includes a drive unit 21, an LED display unit 22, and a brightness measurement unit 23, as shown in FIG. The LED display unit 22 includes a plurality of LEDs 111. The plurality of LEDs 111 are arranged in a matrix. FIG. 1 shows a case where the plurality of LEDs 111 are 2 LEDs in the horizontal direction x 2 LEDs in the vertical direction = 4 LEDs. The plurality of LEDs 111 are LEDs different from the plurality of LEDs 101, but have the same brightness reduction characteristics as the brightness reduction characteristics of the plurality of LEDs 101. The plurality of LEDs 111 are LEDs of the same type as the types of the plurality of LEDs 101. Each LED 112 included in the plurality of LEDs 111 includes an R LED, a G LED, and a B LED (not shown).

The drive unit 21 drives a plurality of LEDs 111.

The brightness measuring unit 23 is arranged so as to face the LED display unit 22 and measures the brightness of a plurality of LEDs 111. As a result, the brightness of the plurality of LEDs 111 can be measured, and the measured brightness of the plurality of LEDs 111 can be averaged. When the brightness of the plurality of LEDs 111 is measured and the measured brightness of the plurality of LEDs 111 is averaged, the variation in the obtained brightness is suppressed as compared with the case where the brightness of only one LED is measured. can do. However, the LED display unit 22 may include only one LED, and the brightness measuring unit 23 may measure the brightness of only one LED. The brightness measuring unit 23 measures the brightness of the R LED, the G LED, and the B LED provided in each LED 112. The luminance measuring unit 23 includes a measuring device that outputs a signal corresponding to the luminance. The measuring device is a photodiode or the like capable of measuring at a wavelength of visible light.

The brightness reduction rate storage unit 18 acquires the relationship between the stored lighting time and the brightness reduction rate based on the result of the brightness measurement performed. The brightness reduction rate storage unit 18 calculates the brightness reduction rate from the brightness obtained by the brightness measurement, and associates the calculated brightness reduction rate with the lighting time of the plurality of LEDs 111 at the time when the brightness measurement is performed. , Acquire the relationship between the lighting time and the brightness reduction rate.

The drive unit 21 drives the plurality of LEDs 111 while the plurality of LEDs 101 are being driven, and continuously lights the plurality of LEDs 111 while the plurality of LEDs 111 are being driven. As a result, the lighting time of the plurality of LEDs 111 is always longer than the maximum lighting time included in the lighting times of the plurality of LEDs 101. Therefore, from the relationship between the lighting time stored in the brightness reduction rate storage unit 18 and the brightness reduction rate, it is possible to select a lighting time that matches the cumulative lighting time of each LED 102, and the brightness corresponding to the selected lighting time. The rate of decline can be selected. The drive unit 21 continuously lights the plurality of LEDs 111 by supplying a drive signal having a duty ratio of 100% to the plurality of LEDs 111.

1.4 Notification of Warnings, etc. As shown in FIG. 1, the LED display device 1 includes an external communication unit 24 and a communication terminal 25.

The brightness reduction rate detection unit 19 outputs a warning or the like from the communication terminal 25 via the external communication unit 24.

1.5 LED blinking and brightness control The blinking and brightness of each LED 102 is controlled by a pulse width modulation (PWM) method. Therefore, the drive unit 14 supplies each LED 102 with a drive signal having a duty ratio proportional to the signal level of each LED 102. Each LED 102 lights up during the on period of the supplied drive signal. As a result, each LED 102 is lit with a brightness proportional to the signal level of each LED 102.

FIG. 2 is a timing chart illustrating PWM drive performed in the LED display device of the first embodiment. FIG. 2A is a diagram illustrating a waveform of a signal including a pulse repeatedly generated in a basic period of PWM drive. FIG. 2B is a diagram illustrating a waveform of a drive signal having a duty ratio of 85%. FIG. 2C is a diagram illustrating a waveform of a drive signal having a duty ratio of 80%.

The basic period of PWM drive shown in FIG. 2A is one frame period or less of the video signal. The drive signal shown in FIG. 2B includes a pulse that is repeatedly generated in the basic cycle of PWM drive and has a pulse width PW1 that is 85% of the basic cycle of PWM drive. The drive signal shown in FIG. 2C includes a pulse that is repeatedly generated in the basic cycle of PWM drive and has a pulse width PW2 that is 80% of the basic cycle of PWM drive. The brightness of each LED 102 when the drive signal shown in FIG. 2B is supplied to each LED 102, and the brightness of each LED 102 when the drive signal shown in FIG. 2C is supplied to each LED 102. Are different from each other. Therefore, the brightness adjustment of each LED 102 can be performed by changing the duty ratio of the drive signal supplied to each LED 102.

1.6 Integration of LED lighting time The brightness of each LED 102 changes for each frame of the displayed image when it changes at the highest speed. Therefore, the integrating unit 16 can accurately calculate the cumulative lighting time of each LED 102 as follows. That is, the integration unit 16 performs an integration process of the lighting time of each LED 102 each time the basic cycle of the PWM drive ends, and in the integration process, the length of the basic cycle of the PWM drive and the length of the basic cycle of the PWM drive. The cumulative lighting time of each LED 102 can be accurately calculated by integrating the product of the drive coefficient indicating the ratio of the lighting time of each LED 102 to. As the drive coefficient of each LED 102, the duty ratio of the drive signal supplied to each LED 102 can be used in the basic period of PWM drive. However, in order to perform the integration processing for each LED 102 each time the basic period of PWM drive ends, a huge amount of arithmetic processing must be performed, and data must be written to the non-volatile memory with high frequency. Must be. Therefore, in the first embodiment, the cumulative lighting time of each LED 102 is calculated by the method described below in order to efficiently perform the integration process.

The integration unit 16 calculates the cumulative lighting time of each LED 102 by performing an integration process of the lighting time of each LED 102 every time the set time elapses. The set time is longer than the length of the basic period of PWM drive. The set time may be a constant time or a changing time.

In the integration process, the integration unit 16 stores the cumulative operating time t1 of the LED display unit 15 in the lighting time storage unit 17. Further, in the integration process, the integration unit 16 calculates the average drive coefficient R2 of each LED 102 indicating the ratio of the cumulative lighting time S1 of each LED 102 to the cumulative operation time t1 from the drive conditions of each LED 102, and the calculated average drive coefficient R2. Is stored in the lighting time storage unit 17. Therefore, the lighting time storage unit 17 also serves as a storage unit for storing the cumulative operating time t1 and the average drive coefficient R2. In the first embodiment, the average drive coefficient R2 is the average duty ratio of the drive signals supplied to each LED 102 before the integration process is performed. As a result, the integration unit 16 updates the cumulative lighting time information including the cumulative operating time t1 and the average drive coefficient R2 stored in the lighting time storage unit 17 every time the set time elapses. The integrating unit 16 updates the cumulative lighting time information for all of the plurality of LEDs 101 at once.

Further, the integration unit 16 calculates the drive coefficient R1 of each LED 102 indicating the ratio of the lighting time of each LED 102 to the operating time of the LED display unit 15 from the drive conditions of each LED 102 when performing the integration process.

Further, the integration unit 16 sets the previous cumulative operating time t0 of the LED display unit 15 stored in the lighting time storage unit 17 in the previous integration process performed before the integration process, the previous average drive coefficient R0 of each LED 102, and the previous integration. The cumulative lighting time S1 of each LED 102 is calculated based on the elapsed time t1-t0 from the processing to the integration processing and the calculated drive coefficient R1 of each LED 102. In the first embodiment, the drive coefficient R1 is the duty ratio of the drive signal supplied to each LED 102 when the previous integration process is performed. Further, in the first embodiment, the previous average drive coefficient R0 is the average duty ratio of the drive signals supplied to each LED 102 until the previous integration process is performed.

The cumulative lighting time S0 of each LED 102 when the previous integration process is performed is the product of the previous cumulative operating time t0 of the LED display unit 15 and the previous average drive coefficient R0 of each LED 102, as shown in equation (1). Represented by.

In the first embodiment, the drive coefficient of each LED 102, that is, the duty ratio of the drive signal supplied to each LED 102 in the entire basic period of PWM drive that has arrived from the previous integration process to the integration process. Is assumed to be R1. Therefore, the cumulative lighting time S1 of each LED 102 when the integration process is performed is the product of the cumulative lighting time S0, the elapsed time t1-t0, and the drive coefficient R1 as shown in the equation (2). It is represented by the sum.

The average drive coefficient R2 of each LED 102 is a coefficient obtained by dividing the cumulative lighting time S1 of each LED 102 by the cumulative operating time t1 of the LED display unit 15, as shown in the equation (3). Therefore, when the equations (1) and (2) are taken into consideration, the average drive coefficient R2 is the previous cumulative operating time t0 of the LED display unit 15 and the previous average of each LED 102, as shown in the equation (3). It is a coefficient obtained by dividing the sum of the product of the drive coefficient R0 and the product of the elapsed time t1-t0 and the drive coefficient R1 of each LED 102 by the cumulative operating time t1.

The integrating unit 16 calculates the average drive coefficient R2 every time the set time elapses from the time when the cumulative operating time of the LED display unit 15 is 0. Further, the integrating unit 16 updates the previous average driving coefficient R1 stored in the lighting time storage unit 17 with the calculated average driving coefficient R2.

When the change in the display pattern displayed on the LED display unit 15 is small, the change in the brightness of each LED 102 is also small, and the change in the duty ratio of the drive signal supplied to each LED 102 is also small. Therefore, when the change in the display pattern displayed on the LED display unit 15 is small, the actual lighting time of each LED 102 and the actual lighting time of each LED 102 are determined even when the set time is sufficiently longer than the length of the basic period of PWM drive. The difference from the cumulative lighting time of each LED 102 calculated from the average drive coefficient R2 is sufficiently small. Therefore, the cumulative lighting time of each LED 102 stored in the lighting time storage unit 17 can be accurately calculated, and the calculated cumulative lighting time of each LED 102 can be used for the luminance correction described below. As a result, the cumulative lighting time of each LED 102 stored in the lighting time storage unit 17 can be accurately calculated while reducing the amount of arithmetic processing for performing the integration processing.

1.7 Relationship between lighting time and brightness reduction rate FIG. 3 shows the relationship between the lighting time of the R, G, and B LEDs and the brightness reduction rate of the R, G, and B LEDs in the LED display device of the first embodiment. It is a graph which shows.

The brightness of the R LED102r, the G LED102g, and the B LED102b is a function of the lighting time t of the R LED102r, the G LED102g, and the B LED102b, respectively, and the lighting of the R LED102r, the G LED102g, and the B LED102b. It decreases as the time t becomes longer. Therefore, as shown in FIG. 3, the brightness reduction rate kr (t) of the LED 102r of R, the brightness reduction rate kg (t) of the LED 102g of G, and the brightness reduction rate kb (t) of the LED 102b of B are respectively. It is a function of the lighting time t of the LED 102r of R, the LED 102g of G and the LED 102b of B, and increases as the lighting time t of the LED 102r of R, the LED 102g of G and the LED 102b of B becomes longer. The brightness reduction rate of the R LED, the G LED, and the B LED provided in each LED 112 also changes in the same manner as the brightness reduction rate of the R LED 102r, the G LED 102g, and the B LED 102b provided in each LED 102.

The brightness reduction rate is usually obtained by prior measurement. However, in the first embodiment, the above-mentioned drive unit 21, LED display unit 22, and luminance measurement unit 23 are incorporated in the LED display device 1, and the incorporated drive unit 21, LED display unit 22, and luminance measurement unit 23 are used. The brightness reduction rates of the plurality of LEDs 111 are measured, and the measured brightness reduction rates of the plurality of LEDs 111 and the lighting times of the plurality of LEDs 111 are stored in the brightness reduction rate storage unit 18. This makes it possible to measure the relationship between the lighting time and the brightness reduction rate in real time.

1.8 Luminance correction method FIG. 4 is a flowchart showing a luminance correction method in the LED display device of the first embodiment.

In step S1 illustrated in FIG. 4, the integration unit 16 determines whether or not the time set from the previous integration process has elapsed. When it is determined that the time set from the previous integration process has elapsed, the integration unit 16 performs the integration process, and when it is determined that the time set from the previous integration process has not elapsed, the integration unit 16 starts from the previous integration process. It is determined again whether or not the set time has elapsed. The set time is a unit time of luminance correction, for example, 100 hours. As a result, the integration unit 16 performs the integration process every time the set time elapses.

In the integration process, the integration unit 16 calculates the cumulative lighting time of the R LED102r, the G LED102g, and the B LED102b, and stores the calculated cumulative lighting time of the R LED102r, G LED102g, and B LED102b in the lighting time storage unit. Store in 17.

In the following step S2, the brightness reduction rate detection unit 19 is stored in the lighting time storage unit 17, the cumulative lighting time of the R LED 102r, the G LED 102g, and the B LED 102b, and the brightness reduction rate storage unit 18. A table showing the relationship between the lighting time of the R LED and the brightness reduction rate of the R LED, a table showing the relationship between the lighting time of the G LED and the brightness reduction rate of the G LED, and the lighting of the B LED. With reference to the table showing the relationship between the time and the brightness reduction rate of the LED B, the brightness reduction rate kr (t) of the LED 102r of R, the brightness reduction rate kg (t) of the LED 102g of G, and the brightness reduction rate of the LED 102b of B Calculate kb (t).

In the following step S3, the luminance reduction rate detection unit 19 determines whether or not the luminance reduction rates kr (t), kg (t) and kb (t) are equal to or less than the threshold values YRth, YGth and YBth, respectively. The luminance reduction rates kr (t), kg (t) and kb (t) determined to be equal to or less than the threshold values YRth, YGth and YBth are output to the correction coefficient calculation unit 20. Steps S4 to S6 are executed for the luminance reduction rates kr (t), kg (t), and kb (t) determined to be equal to or less than the threshold values YRth, YGth, and YBth. Step S7 is executed for the luminance reduction rates kr (t), kg (t) and kb (t) determined not to be equal to or less than the threshold values YRth, YGth and YBth.

In step S4, the correction coefficient calculation unit 20 determines from the brightness reduction rates kr (t), kg (t) and kb (t) determined to be equal to or less than the threshold values YRth, YGth and YBth to the maximum brightness reduction rate krgb (tmax). ) Is selected.

The maximum brightness reduction rate krgb (tmax) is the brightness reduction rate kr (trmax) of the LED 102r of R when the cumulative lighting time t is the maximum cumulative lighting time trmax, and the cumulative lighting time t is the maximum cumulative lighting time tgmax. It is expressed by the equation (4) using the brightness reduction rate kg (tgmax) of the LED 102g of G and the brightness reduction rate kb (tbmax) of the LED 102r of R when the cumulative lighting time t is the maximum cumulative lighting time tbmax. ..

In the following step S5, the correction coefficient calculation unit 20 includes the luminance reduction rates kr (t), kg (t) and kb (t) determined to be equal to or less than the threshold values YRth, YGth and YBth included in the plurality of LEDs 101. The brightness correction coefficient is calculated from the selected maximum brightness reduction rate krgb (tmax) for the LED having.

In the following step S6, the correction coefficient calculation unit 20 outputs the calculated brightness correction coefficient to the brightness correction unit 13. The brightness correction unit 13 corrects the brightness using the input brightness correction coefficient. The brightness correction coefficient is multiplied by the brightness of the LED having the brightness reduction rates kr (t), kg (t) and kb (t) determined to be equal to or less than the thresholds YRth, YGth and YBth before the brightness correction is performed. ..

Brightness correction of R LED 102r, G LED 102g and B LED 102b provided for LEDs having brightness reduction rates kr (t), kg (t) and kb (t) determined to be less than or equal to the thresholds YRth, YGth and YBth. The brightness Rcomp, Gcomp and Bcomp after the above are the brightness reduction rates kr (t), kg (t) and kb (t) at the lighting time t of the LED102r of the R, the LED102g of the G and the LED102b of the B. Using the maximum brightness reduction rate krgb (tmax) and the brightness Rp, Gp and Bp before the brightness correction of the LED 102r of the R, the LED 102g of the G and the LED 102b of the B is performed, the equation (5), the equation ( It is expressed by 6) and equation (7).

The luminance Rp, Gp and Bp appearing in the equations (5), (6) and (7) before the luminance correction is the initial luminance R0 of the LED 102r of the R, the LED 102g of the G and the LED 102b of the B. , G0 and B0, and the luminance reduction rates kr (t), kg (t) and kb (t) are expressed by equations (8), (9) and (10).

By substituting equations (8), (9) and (10) into equations (5), (6) and (7), equations (11), (12) and (13) can be obtained. Obtainable. From equations (11), (12) and (13), the luminance Rcomp, Gcomp and Bcomp after the luminance correction has the initial luminance R0, G0 and B0 as the maximum luminance reduction rate krgb (tmax). It can be understood that it can be obtained by using and making a unified correction.

The brightness correction of each LED 102 can be performed by changing the duty ratio of the drive signal supplied to each LED 102 in the same manner as the brightness adjustment of each LED 102. For example, if the maximum luminance reduction rate krgb (tmax) is 0.2 and the luminance reduction rate kr (t) is 0.1, the luminance correction coefficient (5) multiplied by the luminance Rp before the luminance correction is performed in Eq. (5). Since 1-krgb (tmax)) / (1-kr (t)) becomes (1-0.2) / (1-0.1) = 8/9, the brightness is corrected by setting the duty ratio to 8/9. It can be carried out.

In step S7, the brightness reduction rate detection unit 19 includes the number of LEDs included in the plurality of LEDs 101 and having brightness reduction rates kr (t), kg (t) and kb (t) larger than the threshold values YRth, YGth and YBth. Is counted, and the number of the counted LEDs is output from the communication terminal 25 via the external communication unit 24. Further, when the number of counted LEDs becomes the first number Dt0 or more, the brightness reduction rate detection unit 19 outputs a warning from the communication terminal 25 via the external communication unit 24. The brightness reduction rate detection unit 19 notifies the user of the LED display device 1 of the warning by outputting a warning from the communication terminal 25. As a result, the user of the LED display device 1 can grasp the replacement time of the LED display unit 15. As a result, it is possible to prevent the number of LEDs having brightness reduction rates kr (t), kg (t) and kb (t) larger than the threshold values YRth, YGth and YBth from being excessively increased and making the LEDs conspicuous. ..

After steps S6 and S7 are executed, step S1 is executed again.

The brightness of LEDs having brightness reduction rates kr (t), kg (t) and kb (t) larger than the thresholds YRth, YGth and YBth is not corrected. Therefore, the brightness correction coefficient multiplied by the brightness Rp, Gp and Bp before the brightness correction of the R LED 102r, the G LED 102g and the B LED 102b provided in the LED is "1", and the brightness correction is performed. The previous brightness Rp, Gp and Bp are unchanged.

1.9 Effect of Invention of Embodiment 1 According to the invention of Embodiment 1, an LED having brightness reduction rates kr (t), kg (t) and kb (t) below the thresholds YRth, YGth and YBth. The brightness correction is performed, but the brightness correction of the LED having the brightness reduction rates kr (t), kg (t) and kb (t) larger than the thresholds YRth, YGth and YBth is not performed. Further, the brightness reduction rates of the R LED 102r, the G LED 102g and the B LED 102b provided in the LED having the brightness reduction rates kr (t), kg (t) and kb (t) equal to or less than the threshold values YRth, YGth and YBth are determined. It is matched with the maximum brightness reduction rate krgb (tmax). As a result, the uniformity of the overall brightness of the LED display unit 15 and the white balance can be maintained, and the variation in the brightness of the LED display unit 15 can be suppressed.

When the LED display device 1 displays a surveillance image, in many cases, the LED display device 1 displays a still image for a long time, and only some LEDs included in the plurality of LEDs 101 take a long time. It emits light across. Therefore, the brightness of the LED that emits light over a long period of time is significantly lower than the brightness of the remaining LED. In such a case, when the control for maintaining the uniformity of the total brightness of the plurality of LEDs 101 is performed, the total brightness of the plurality of LEDs 101 is greatly reduced in accordance with the LED having the significantly reduced brightness. On the other hand, according to the invention of the first embodiment, the remaining LEDs are excluded except for the LEDs having brightness reduction rates kr (t), kg (t) and kb (t) larger than the threshold values YRth, YGth and YBth. Control is performed to maintain the uniformity of the brightness of the LED. Therefore, the total brightness of the plurality of LEDs 101 is not significantly reduced in accordance with the LED having the significantly reduced brightness. In this case, the excluded LEDs have a brightness smaller than the brightness Rcomp, Gcomp and Bcomp after the brightness correction of the surrounding LEDs is performed, but when the LED display device 1 displays the surveillance image, Since the change in the displayed image is small, the difference between the brightness of the excluded LED and the brightness of the surrounding LEDs is not noticeable. Furthermore, when the brightness reduction rate of the LED counts the number of LEDs of YRth, YGth and YBth or more and reaches a certain number of Dt0 or more, it can be notified to the external control device as warning information, so that the user can display the LED. It is possible to grasp the appropriate replacement time of the part 10. By replacing the appropriate LED display unit 10, the number of LEDs whose brightness reduction rate has decreased by a threshold value or more increases, so that it is possible to avoid a symptom that the LEDs whose brightness is not corrected are conspicuous. Normally, it is possible to monitor the energization time of the LED display device and notify the external control device of the replacement time of the LED display unit 10 when the energization time exceeds a certain time, but it is actually as in this embodiment. Since the replacement time is detected by the light emission time of the LED, it is possible to notify the appropriate replacement time without notifying the replacement sign of the LED display even though the brightness of each LED is not actually lowered. it can.

Further, according to the invention of the first embodiment, every time the set time elapses, the cumulative operating time t1 of the LED display unit 15 and the average drive coefficient R2 of each LED 102 are stored in the lighting time storage unit 17, and the brightness is increased. When the correction is performed, the cumulative lighting time of each LED 102 is calculated from the stored cumulative operating time t1 and the average drive coefficient R2, and the brightness correction of the plurality of LEDs 101 is performed based on the calculated cumulative lighting time. As a result, the amount of data stored in the lighting time storage unit 17 can be reduced.

Further, according to the invention of the first embodiment, the integration process is performed every time a set time longer than the length of the basic cycle of PWM drive elapses. Therefore, the amount of arithmetic processing and the amount of data written to the non-volatile memory can be significantly reduced. However, the cumulative lighting time may be calculated each time the basic cycle of PWM control ends, and the calculated cumulative lighting time may be stored in the lighting time storage unit 17 each time the set time elapses.

1.10 Modification Example In the first embodiment, the integration unit 16 stores the cumulative lighting time information stored in the lighting time storage unit 17 at once for all of the plurality of LEDs 101 every time the set time elapses. To update. However, the integrating unit 16 does not have to update the cumulative lighting time information for all of the plurality of LEDs 101 at once. For example, the integrating unit 16 may divide the plurality of LEDs 101 into a plurality of LED groups, and sequentially update the cumulative lighting time information for the plurality of LED groups while the plurality of frames are displayed. In this case, the integrating unit 16 updates the cumulative lighting time information for one LED group every time one frame is displayed, and updates the cumulative lighting time information while a plurality of frames are displayed. It patrols, and as a result, updates the cumulative lighting time information for all of the plurality of LEDs 101. When the cumulative lighting time information is updated for all of the plurality of LEDs 101 at once, the load applied to the integrating unit 16 and the lighting time storage unit 17 is intensively increased when the cumulative lighting time information is updated. When the cumulative lighting time information is sequentially updated for a plurality of LED groups while the frame is displayed, the load applied to the integrating unit 16 and the lighting time storage unit 17 is leveled.

Further, in the first embodiment, the relationship between the lighting time and the brightness reduction rate, which is stored in the brightness reduction rate storage unit 18 and referred to by the brightness reduction rate detection unit 19, is a plurality of LEDs 111 performed by the brightness measurement unit 23. Obtained from the result of the brightness measurement of. However, when the LED display device 1 is shipped from the factory, the brightness reduction rate storage unit 18 stores the relationship between the lighting time and the brightness reduction rate, and the relationship between the stored lighting time and the brightness reduction rate is the brightness reduction rate. It may be referred to by the detection unit 19.

2 Embodiment 2
1 to 4 are also views for explaining the LED display device of the second embodiment.

The LED display device 2 of the second embodiment is different from the LED display device 1 of the first embodiment mainly in the following points. Regarding points not described below, the configuration adopted in the LED display device 1 of the first embodiment is also adopted in the LED display device 2 of the second embodiment.

In the LED display device 1 of the first embodiment, as described above, the drive coefficients of each LED 102, that is, each of them, are in the entire basic period of PWM drive that has arrived from the previous integration process to the integration process. It is assumed that the duty ratio of the drive signal supplied to the LED 102 is R1. Then, as shown in Eq. (2), the elapsed time t1-t0 is multiplied by the drive coefficient R1. On the other hand, in the LED display device 2 of the second embodiment, the drive coefficient of each LED 102, that is, each of them, is used in the entire basic period of PWM drive that has arrived from the previous integration process to the integration process. It is assumed that the duty ratio of the drive signal supplied to the LED 102 is the average of the previous average drive coefficient R0 and the drive coefficient R1. Thereby, the error of the calculated cumulative lighting time of each LED 102 from the actual lighting time of each LED 102 can be reduced.

In this case, the cumulative lighting time S0 of each LED 102 when the previous integration process is performed is the previous cumulative operating time t0 of the LED display unit 15 and the previous average drive coefficient of each LED 102, as shown in the equation (14). It is represented by the product of R0. The previous average drive coefficient R0 is stored in the lighting time storage unit 17.

As shown in Equation (15), the cumulative lighting time S1 of each LED 102 when the integration process is performed is the cumulative lighting time S0, the elapsed time t1-t0, the average of the previous average drive coefficient R0, and the average drive coefficient R1. It is represented by the product of and the sum of.

From equations (14) and (15), the average drive coefficient R2 of each LED 102 stored in the lighting time storage unit 17 at the cumulative operating time t1 is derived as shown in equation (16). The average drive coefficient R2 of each LED 102 is the product of the previous cumulative operating time t0 of the LED display unit 15 and the previous average drive coefficient R0 of each LED 102, and the average of the elapsed time t1-t0, the previous average drive coefficient R0, and the drive coefficient R1. It is a coefficient obtained by dividing the product of and the sum of and by the cumulative operating time t1 of the LED display unit 15.

The integrating unit 16 calculates the average drive coefficient R2 every time the set time elapses from the time when the cumulative operating time of the LED display unit 15 is 0, and the previous average drive coefficient R1 stored in the lighting time storage unit 17. Is updated with the calculated average drive coefficient R2.

The invention of the second embodiment has the same effect as that of the invention of the first embodiment.

Further, according to the invention of the second embodiment, it is possible to reduce the error of the calculated cumulative lighting time of each LED 102 from the actual lighting time of each LED 102. As a result, the luminance correction can be performed with higher accuracy.

3 Embodiment 3
1 to 3 are also views for explaining the LED display device of the third embodiment.

The LED display device 3 of the third embodiment is different from the LED display device 1 of the first embodiment mainly in the following points. Regarding points not described below, the configuration adopted in the LED display device 1 of the first embodiment is also adopted in the LED display device 3 of the third embodiment.

In the LED display device 1 of the first embodiment, the threshold values YRth, YGth and YBth to be compared with the luminance reduction rates kr (t), kg (t) and kb (t) are not changed. In addition, brightness correction is performed on LEDs having brightness reduction rates kr (t), kg (t) and kb (t) equal to or less than the thresholds YRth, YGth and YBth. However, the brightness correction is not performed for the LED having the brightness reduction rate kr (t), kg (t) and kb (t) larger than the threshold values YRth, YGth and YBth. On the other hand, in the LED display device 3 of the third embodiment, the brightness reduction rates kr (t), kg (t) and kb (t) contained in the plurality of LEDs 101, which are larger than the threshold values YRth, YGth and YBth, are set. When the number of LEDs possessed is equal to or greater than the second number Dt1, the thresholds YRth, YGth and YBth are changed to larger thresholds YRth2, YGth2 and YBth2. In addition, brightness correction will be performed on LEDs having brightness reduction rates kr (t), kg (t) and kb (t) equal to or less than the changed thresholds YRth2, YGth2 and YBth2.

FIG. 5 is a flowchart showing a brightness correction method in the LED display device of the third embodiment.

In steps S1 to S7 shown in FIG. 5, the same processes as those performed in steps S1 to S7 shown in FIG. 4 are performed.

In step S10 following step S7, the number of LEDs having a brightness reduction rate kr (t), kg (t) and kb (t) larger than the threshold values YRth, YGth and YBth counted by the brightness reduction rate detection unit 19. Determines whether or not is equal to or greater than the second number Dt1. If it is determined that the number of the counted LEDs is equal to or greater than the second number Dt1, step S1 is executed again after step S11 is executed. If it is determined that the number of the counted LEDs is not equal to or greater than the second number Dt1, step S1 is executed again without executing step S11.

In step S11, the luminance reduction rate detection unit 19 changes the threshold values YRth, YGth and YBth to larger threshold values YRth2, YGth2 and YBth2.

According to steps S10 and S11, when the number of counted LEDs is equal to or greater than the second number Dt1, the brightness correction is performed based on the changed thresholds YRth2, YGth2, and YBth2. If the number of counted LEDs is not equal to or greater than the second number Dt1, the thresholds YRth, YGth and YBth are not changed to other thresholds, and the brightness is corrected based on the current thresholds YRth, YGth and YBth. Continues to be done.

The invention of the third embodiment has the same effect as that of the invention of the first embodiment.

Further, according to the invention of the third embodiment, the brightness is reduced when the number of LEDs having the brightness reduction rates kr (t), kg (t) and kb (t) larger than the thresholds YRth, YGth and YBth is increased. Luminance correction is performed again after the thresholds YRth, YGth and YBth compared with the rates kr (t), kg (t) and kb (t) are changed to the larger thresholds YRth2, YGth2 and YBth2. As a result, the overall brightness of the LED display unit 15 is reduced, but the number of LEDs for which the brightness correction is not performed is reduced. Therefore, it is possible to suppress the conspicuousness of the LEDs for which the brightness correction is not performed. Brightness uniformity is improved.

4 Embodiment 4
1 to 3 are also views for explaining the LED display device of the fourth embodiment.

The LED display device 4 of the fourth embodiment is different from the LED display device 1 of the first embodiment mainly in the following points. Regarding points not described below, the configuration adopted in the LED display device 1 of the first embodiment is also adopted in the LED display device 4 of the fourth embodiment.

In the LED display device 1 of the first embodiment, the threshold values YRth, YGth and YBth are not changed. Further, when the number of LEDs having brightness reduction rates kr (t), kg (t) and kb (t) larger than the threshold values YRth, YGth and YBth contained in the plurality of LEDs 101 is the first number Dt0 or more. A warning is output to. On the other hand, in the LED display device 4 of the fourth embodiment, it is based on the minimum brightness reduction rates kr (t) _min, kg (t) _min and kb (t) _min included in the brightness reduction rates of the plurality of LEDs 101. The thresholds YRth, YGth and YBth are changed. Further, for determining the necessity of warning indicating the brightness reduction rate of each LED with respect to the brightness of the LEDs having the minimum brightness reduction rates kr (t) _min, kg (t) _min and kb (t) _min included in the plurality of LEDs 101. The brightness reduction rate is calculated, and a warning is output when the number of LEDs having the brightness reduction rate for determining the necessity of warning equal to or higher than the set threshold value becomes larger than the set number.

FIG. 6 is a flowchart showing a brightness correction method in the LED display device of the fourth embodiment.

In steps S1, S2, S3, S4, S4 and S6 shown in FIG. 6, the same processes as those performed in steps S1, S2, S3, S4, S4 and S6 shown in FIG. 4 are performed. Will be.

In step S41 following step S2, the brightness reduction rate detection unit 19 has the minimum brightness reduction rates kr (t) _min, kg (t) _min and kb (t) _min included in the brightness reduction rates of the plurality of LEDs 101. Select the LED.

In step S42 following step S41, the brightness reduction rate detection unit 19 calculates the brightness reduction rate for determining the necessity of warning, which indicates the brightness reduction rate of each LED with respect to the brightness of the selected LED. Further, the brightness reduction rate detection unit 19 counts the number of LEDs having a brightness reduction rate for determining the necessity of warning equal to or higher than the set threshold value. In the fourth embodiment, the set threshold value is a constant threshold value.

In step S43 following step S42, whether or not the number of LEDs having the brightness reduction rate for determining the necessity of warning above the set threshold value counted by the brightness reduction rate detection unit 19 is larger than the set number. Is determined. In the fourth embodiment, the set number is a constant number. If it is determined that the number of counted LEDs is greater than the set number, step S45 is executed after step S44 is executed. If it is determined that the number of counted LEDs is less than or equal to the set number, step S45 is executed without executing step S44.

In step S44, the brightness reduction rate detection unit 19 outputs a warning from the communication terminal 25 via the external communication unit 24. The output warning is a warning that notifies the user that the LED display unit 15 has deteriorated and prompts early replacement of the substrate or the like provided in the LED display device 4.

In step S45, the brightness reduction rate detection unit 19 extracts the minimum brightness reduction rates kr (t) _min, kg (t) _min and kb (t) _min included in the brightness reduction rates of the plurality of LEDs 101. Further, the brightness reduction rate detection unit 19 calculates the threshold values YRth, YGth and YBth based on the extracted minimum brightness reduction rates kr (t) _min, kg (t) _min and kb (t) _min. The calculated thresholds YRth, YGth and YBth are represented by equations (17), (18) and (19) using constants Tha greater than 1.

The invention of the fourth embodiment has the same effect as that of the invention of the first embodiment.

Further, in the invention of the first embodiment, the brightness correction of the LED having the brightness reduction rates kr (t), kg (t) and kb (t) below a certain threshold value YRth, YGth and YBth has the uniformity of brightness. It is performed so as to be maintained, and the brightness correction of the LED having the brightness reduction rates kr (t), kg (t) and kb (t) larger than the threshold values YRth, YGth and YBth is not performed. Therefore, the number of LEDs having brightness reduction rates kr (t), kg (t) and kb (t) larger than the threshold values YRth, YGth and YBth and for which brightness correction is not performed increases due to aged deterioration. As a result, it may be difficult to maintain the uniformity of brightness and white balance of the LED display unit 15. In addition, the brightness difference of the LED for which the brightness correction is not performed is conspicuous, and the quality of the image displayed on the LED display unit 15 may be impaired.

On the other hand, in the invention of the fourth embodiment, the calculation is performed based on the minimum brightness reduction rates kr (t) _min, kg (t) _min and kb (t) _min included in the brightness reduction rates of the plurality of LEDs 101. Luminance correction is performed for LEDs having brightness reduction rates kr (t), kg (t) and kb (t) below the thresholds YRth, YGth and YBth, and the brightness reduction rate kr ( Luminance correction is not performed for LEDs with t), kg (t) and kb (t). Therefore, when the brightness correction is performed so that the uniformity of the brightness is maintained, the brightness of the LED having the minimum brightness reduction rates kr (t) _min, kg (t) _min and kb (t) _min is constant. Only the LED having the brightness lower than the threshold value is the LED for which the brightness correction is not performed. As a result, when the variation in the brightness of the plurality of LEDs 101 is small, the number of LEDs for which the brightness correction is not performed can be reduced, and it becomes easy to maintain the uniformity of the brightness of the LED display unit 15. In addition, it is possible to suppress the difference in brightness of the LEDs for which the brightness correction is not performed from being conspicuous, and it is possible to suppress the deterioration of the quality of the image displayed on the LED display unit 15.

It should be noted that, within the scope of the present invention, each embodiment can be freely combined, and each embodiment can be appropriately modified or omitted.

Although the present invention has been described in detail, the above description is exemplary in all aspects and the invention is not limited thereto. It is understood that a myriad of variations not illustrated can be envisioned without departing from the scope of the invention.

1,2,3,4 LED display device, 11 input terminal, 12 video signal processing circuit, 13 brightness correction unit, 14 drive unit, 15 LED display unit, 16 integration unit, 17 lighting time storage unit, 18 brightness reduction rate storage Unit, 19 Brightness reduction rate detection unit, 20 Correction coefficient calculation unit, 21 Drive unit, 22 LED display unit, 23 Brightness measurement unit, 24 External communication unit, 25 Communication terminals, 101 Multiple LEDs, 102 Each LED, 111 Multiple LED, 112 each LED.

Claims

An LED display with multiple LEDs and
An integrating unit that calculates the cumulative lighting time of each LED by performing an integration process of the lighting time of each LED included in the plurality of LEDs.
A brightness reduction rate storage unit that stores the relationship between the lighting time of the LED and the brightness reduction rate of the LED,
The brightness reduction rate of each LED is detected from the cumulative lighting time and the relationship to obtain the brightness reduction rate of the plurality of LEDs, and the brightness reduction rate below the threshold value is selected from the brightness reduction rates of the plurality of LEDs. Rate detector and
A correction coefficient calculation unit that calculates a brightness correction coefficient based on the brightness reduction rate below the threshold value,
A brightness correction unit that outputs a video signal that has been corrected for brightness by performing brightness correction on the video signal using the brightness correction coefficient, and a brightness correction unit.
A drive unit that drives the plurality of LEDs according to the brightness-corrected video signal, and
An LED display device comprising.
The LED display device according to claim 1, wherein the correction coefficient calculation unit calculates the brightness correction coefficient based on the maximum brightness reduction rate included in the brightness reduction rate below the threshold value.
With another LED having the same brightness reduction characteristics as the brightness reduction characteristics of the plurality of LEDs,
A brightness measuring unit that measures the brightness of the other LED,
With more
The LED display device according to claim 1 or 2, wherein the brightness reduction rate storage unit acquires the relationship based on the measurement result.
With more storage
The integrating unit
The integration process is performed every time the set time elapses.
In the integration process, the cumulative operating time of the LED display unit is stored in the storage unit, the average drive coefficient of each LED indicating the ratio of the cumulative lighting time to the cumulative operating time is calculated, and the average drive coefficient is calculated. Stored in the storage unit
From the drive conditions of each LED when performing the integration process, the drive coefficient of each LED indicating the ratio of the lighting time of each LED to the operating time of the LED display unit is calculated.
Based on the previous cumulative operating time and the previous average drive coefficient stored in the storage unit in the previous integration process performed before the integration process, the elapsed time from the previous integration process to the integration process, and the drive coefficient. , The LED display device according to any one of claims 1 to 3 for calculating the cumulative lighting time.
The average driving coefficient is a coefficient obtained by dividing the sum of the product of the previous cumulative operating time and the previous average driving coefficient and the product of the elapsed time and the driving coefficient by the cumulative operating time. The LED display device according to claim 4.
The average drive coefficient is the sum of the product of the previous cumulative operating time and the previous average drive coefficient, the product of the elapsed time, the previous average drive coefficient, and the average of the drive coefficients, and the cumulative operating time. The LED display device according to claim 4, which is a coefficient obtained by dividing by.
The average drive coefficient is an average duty ratio of drive signals supplied to each of the LEDs before the integration process is performed.
The drive coefficient is a duty ratio of a drive signal supplied to each of the LEDs when the previous integration process is performed.
The LED display device according to any one of claims 4 to 6, wherein the previous average drive coefficient is an average duty ratio of drive signals supplied to the respective LEDs by the time the previous integration process is performed.
Claims 1 to 7 that the brightness reduction rate detecting unit notifies a warning when the number of LEDs having a brightness reduction rate larger than the threshold value among the plurality of LEDs is equal to or greater than the first number. One of the LED display devices.
The brightness reduction rate detection unit is requested to change the threshold value to a larger threshold value when the number of LEDs having a brightness reduction rate larger than the threshold value among the plurality of LEDs is the second number or more. The LED display device according to any one of Items 1 to 8.
The LED display device according to any one of claims 1 to 9, wherein the brightness reduction rate detection unit calculates the threshold value based on the minimum brightness reduction rate included in the brightness reduction rates of the plurality of LEDs.
a) A step of calculating the cumulative lighting time of each LED by integrating the lighting time of each LED included in a plurality of LEDs provided in the LED display unit provided in the LED display device.
b) A step of detecting the brightness reduction rate of each LED from the cumulative lighting time and the relationship between the LED lighting time and the brightness reduction rate of the LED to obtain the brightness reduction rate of the plurality of LEDs.
c) A step of selecting a brightness reduction rate below the threshold value from the brightness reduction rates of the plurality of LEDs, and
d) The process of calculating the brightness correction coefficient according to the brightness reduction rate below the threshold value, and
e) The process of performing brightness correction on the video signal using the brightness correction coefficient and outputting the video signal with the brightness correction performed.
f) The process of driving the plurality of LEDs according to the image signal for which the brightness has been corrected, and
Luminance correction method including.