JP2018072531A - Led display device and luminance correction method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED display device and a luminance correction method therefor with which it is possible to improve the accuracy of correcting LED luminance.SOLUTION: An LED display device 100A comprises a first LED display unit 10 having each of a plurality of first LEDs 1 as a pixel, and a first drive unit 5 for driving the first LED display unit 10 on the basis of inputted display data. The LED display device 100A includes an integration unit 6 and a luminance correction unit 4. The integration unit 6 calculates, at random time intervals, a cumulative lighting time in which the lighting time of each of the plurality of first LEDs 1 are individually integrated. The luminance correction unit 4 individually corrects the luminance of each of the plurality of first LEDs 1 on the basis of the cumulative lighting time of each of the plurality of first LEDs 1 calculated by the integration unit 6.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an LED display device and a luminance correction method thereof, and more particularly, an LED that displays a plurality of LEDs (Light Emitting Diodes) in a matrix and displays video information by controlling blinking of each LED. The present invention relates to a display device and a luminance correction method thereof.

  An LED display device using each of a plurality of LEDs as a pixel is often used for advertisement display indoors and outdoors due to the technological development and cost reduction of LEDs. Until now, these LED display devices have mainly displayed moving images such as natural images and animations. However, the viewing distance becomes shorter as the pixel pitch becomes narrower. It is also used for monitoring and other purposes. Especially in monitoring applications, LED display devices often display images that are close to still images input from, for example, a personal computer.

  The brightness of the LED decreases as the lighting time increases. For this reason, the luminance reduction rate of each LED differs depending on the content of the image displayed on the LED display unit, and as a result, luminance variation and color variation occur for each pixel.

  In order to reduce these luminance variations and color variations, a method of detecting the luminance of the LED display unit and correcting the luminance of each LED based on the detection result, and individually integrating the lighting time of each LED. A method is proposed in which a luminance correction coefficient is calculated based on the integration result and the relationship between the measured lighting time and the luminance of the LED, and the luminance of each LED is individually corrected based on the luminance correction coefficient. (For example, see Patent Document 1 and Patent Document 2).

Japanese Patent Laid-Open No. 11-15437 JP 2006-330158 A

  However, in the conventional technique in which the lighting time of each LED is individually integrated and the luminance of each LED is individually corrected based on this integration result, the timing for performing this integration processing is often a fixed period. In this case, there is no problem when the LED display unit displays a still image in which the image does not change, but when displaying an image in which the LED blinks at a constant cycle such as a warning signal in a monitoring application, the LED blinks. The cycle may overlap with the cycle of the integration process. As a result, there arises a problem that the integration process is performed as if the LED is actually blinking, even though the LED is blinking.

  Therefore, the present invention has been made in view of the above problems, and the lighting times of the LEDs are individually integrated at random time intervals, and the luminance of each LED is individually corrected based on the integration result. Accordingly, an object of the present invention is to provide an LED display device and a luminance correction method thereof that can improve the accuracy of LED luminance correction as compared with the case where integration is performed at a constant period.

  The LED display device according to the present invention is an LED display device that includes an LED display unit having each of a plurality of LEDs as a pixel and a drive unit that drives the LED display unit based on input display data. The LED display device includes an integration unit and a luminance correction unit. The integrating unit calculates an accumulated lighting time obtained by individually integrating the lighting times of the plurality of LEDs at random time intervals. The brightness correction unit individually corrects the brightness of each of the plurality of LEDs based on the cumulative lighting time of each of the plurality of LEDs calculated by the integration unit.

  In addition, the brightness correction method of the LED display device according to the present invention includes an LED display unit having each of a plurality of LEDs as a pixel, and a drive unit that drives the LED display unit based on input display data. It is a brightness correction method for the apparatus. The brightness correction method for the LED display device is calculated in (a) a step of calculating a cumulative lighting time obtained by individually integrating lighting times of a plurality of LEDs at random time intervals, and (b) a step (a). And a step of individually correcting the luminance of each of the plurality of LEDs based on the cumulative lighting time of each of the plurality of LEDs.

  According to the present invention, since the accumulated lighting time of each of the plurality of LEDs is calculated at random time intervals, even when the LED blinks at a constant cycle, the blinking cycle of the LED and the accumulated lighting time of each of the plurality of LEDs are calculated. It is possible to suppress the coincidence with the timing at which is calculated. Thereby, it is possible to prevent the accumulated lighting time from being calculated as if the LED is lit or extinguished even though the LED is actually blinking. Thus, the accuracy of the brightness correction of the LED can be improved by calculating the accumulated lighting time of the LED more accurately.

1 is a block diagram illustrating a configuration of an LED display device according to Embodiment 1. FIG. It is a figure for demonstrating PWM drive. It is a figure which shows the relationship between the accumulation lighting time in 1st LED, and a luminance fall rate. It is a figure which shows the relationship between the cumulative lighting time in 2nd LED, and a luminance fall rate. It is a flowchart which shows the operation | movement of a brightness correction process. It is a figure which shows the relationship between blink of 1st LED and the timing of an integration process. It is a figure which shows the duty ratio for every integration process, and accumulation operation time. It is a figure which shows the calculation result for every integration process in an integration process (1). It is a figure which shows the maximum accumulation lighting time and brightness | luminance fall rate in each of integration processing (1)-(3). It is a figure which shows the calculation result for every integration process in an integration process (2). It is a figure which shows the calculation result for every integration process in an integration process (3). 6 is a block diagram showing a configuration of an LED display device according to Embodiment 2. FIG. It is a figure which shows the relationship between blink of 1st LED and the timing of an integration process. FIG. 6 is a block diagram showing a configuration of an LED display device according to Embodiment 3. It is a figure which shows timing information. FIG. 6 is a block diagram illustrating a configuration of an LED display device according to a fourth embodiment. It is a block diagram which shows the hardware constitutions of a LED display apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Embodiment 1>
<Configuration of LED display device>
FIG. 1 is a block diagram showing an example of the configuration of an LED display device 100A according to Embodiment 1 of the present invention. As shown in FIG. 1, the LED display device 100 </ b> A includes an input terminal 2, a video signal processing circuit 3, a luminance correction unit 4, a first drive unit 5, a first LED display unit 10, an integration unit 6, and a lighting time storage unit 7. Is provided. The LED display device 100 </ b> A further includes a drive data generation unit 16, a second drive unit 8, a second LED display unit 20, a luminance measurement unit 9, a luminance reduction rate storage unit 11, and a correction coefficient calculation unit 12.

  The first LED display unit 10 includes a plurality of first LEDs 1 arranged in a matrix as pixels. In the example of FIG. 1, the first LED display unit 10 includes a total of 16 first LEDs 1 of 4 × 4. In the present embodiment, the first LED 1 is an LED for full-color display, and includes three LED elements 1a of red (R), green (G), and blue (B).

  Display data including video information such as characters, symbols, and graphics is input to the input terminal 2 from an external device (not shown).

  The video signal processing circuit 3 performs processing for selecting a region necessary for video display and video signal processing such as gamma correction on display data input via the input terminal 2. The video signal processing circuit 3 outputs display data subjected to the video signal processing to the luminance correction unit 4.

  The brightness correction unit 4 individually corrects the brightness of each of the plurality of first LEDs 1 with respect to display data processed by the video signal processing circuit 3 based on a correction coefficient calculated by a correction coefficient calculation unit 12 described later. The brightness correction process is performed. The brightness correction unit 4 outputs the display data that has been subjected to the brightness correction process to the first drive unit 5.

  The first drive unit 5 drives the first LED display unit 10 based on the display data on which the luminance correction process has been performed by the luminance correction unit 4. Thereby, the video based on the display data on which the video signal processing and the luminance correction processing are performed is displayed on the first LED display unit 10.

  The integrating unit 6 individually determines the lighting times of the plurality of first LEDs 1 based on the driving conditions for the first driving unit 5 to drive the first LED display unit 10, that is, the display data used to drive the plurality of first LEDs 1 respectively. The cumulative lighting time accumulated in is calculated. The accumulated lighting time of each of the plurality of first LEDs 1 calculated by the integrating unit 6 is stored in the lighting time storage unit 7.

  The second LED display unit 20 includes a second LED 21 that is the same LED as the first LED 1. Here, the same LED as the first LED 1 means an LED having the same luminance reduction characteristic with respect to the lighting time as the first LED 1. In the present specification, for the sake of explanation, the LED included in the first LED display unit 10 is referred to as “first LED 1”, and the LED included in the second LED display unit 20 is referred to as “second LED 21”. In the example of FIG. 1, the second LED display unit 20 includes a total of four second LEDs 21 of 2 × 2 in the vertical direction. The second LED 21 has three LED elements 21a of red (R), green (G), and blue (B). The red (R), green (G), and blue (B) LED elements 21a are the same LED elements as the red (R), green (G), and blue (B) LED elements 1a, respectively. Here, the same LED element as the LED element 1a means an LED element having the same luminance reduction characteristic as the LED element 1a with respect to the lighting time.

  The second drive unit 8 drives the second LED display unit 20 based on the drive data generated by the drive data generation unit 16.

  The luminance measuring unit 9 measures the luminance of the second LED display unit 20, that is, the luminance of the second LED 21.

  The luminance reduction rate storage unit 11 stores the luminance reduction rate of the second LED 21 in which the luminance of the second LED 21 measured by the luminance measurement unit 9 is associated with the cumulative lighting time of the second LED 21.

  The correction coefficient calculation unit 12 performs luminance correction based on the cumulative lighting time of each of the plurality of first LEDs 1 stored in the lighting time storage unit 7 and the luminance reduction rate of the second LED 21 stored in the luminance reduction rate storage unit 11. A correction coefficient used for the luminance correction processing in the unit 4 is calculated.

<Brightness correction processing>
Hereinafter, the luminance correction process performed by the luminance correction unit 4 will be described.

  In the following description, in order to simplify the description, when there is no need to particularly distinguish each of the three color LED elements 1a included in the first LED 1, these are collectively referred to simply as the first LED 1. In addition, when it is not necessary to particularly distinguish the three-color LED elements 21a included in the second LED 21, these are collectively referred to simply as the second LED 21. Therefore, various processes for the first LED 1 described below indicate processes performed for each of the three color LED elements 1a, and processes for the second LED 21 are performed for each of the three color LED elements 21a. Shows the processing.

  In the luminance adjustment of the first LED 1, a PWM (Pulse Width Modulation) method is used. FIG. 2 is a diagram for explaining PWM drive. In FIG. 2, a waveform PF indicates a basic period (also referred to as “one frame”) in PWM driving. Hereinafter, this basic period is referred to as a “PWM basic period”. Waveform PW1 and waveform PW2 show examples of drive waveforms when the duty ratio is 85% and 80%, respectively. Thus, the brightness | luminance of 1st LED1 can be adjusted by changing the duty ratio of the drive waveform which drives 1st LED1. Specifically, the larger the duty ratio of the drive waveform, the longer the time during which the first LED 1 is lit within the PWM basic period, and the user visually recognizes that the luminance of the first LED 1 is higher.

  The integrating unit 6 calculates an accumulated lighting time obtained by individually integrating the lighting times of the plurality of first LEDs 1. In the process of integrating the cumulative lighting times of each of the plurality of first LEDs 1, the luminance of the first LED 1 changes for each frame of display data at the shortest time, so that the multiplication result of the time of the PWM basic period and the duty ratio of the drive waveform is PWM. It is desirable to integrate every basic period. However, an enormous amount of integration processing is required to perform integration processing for each PWM basic period for each of the plurality of first LEDs 1. Therefore, the LED display device 100A according to the present embodiment performs the integration process more efficiently by the method described below.

<Integration processing at regular intervals>
Hereinafter, the integration process performed by the integration unit 6 will be described. In the present embodiment, the integration unit 6 performs integration processing for individually integrating the lighting times of the plurality of first LEDs 1 at random time intervals, as will be described later. A case where the unit 6 performs integration processing at a constant period will be described.

  The accumulating unit 6 uses the accumulated lighting time obtained by individually integrating the lighting times of the plurality of first LEDs 1 as the first LED display unit 10 is driven by the first driving unit 5, that is, each of the plurality of first LEDs 1 is driven first. It is calculated by multiplying the cumulative operation time driven by the unit 5 and the duty ratio (hereinafter also referred to as “average drive coefficient”) obtained by individually averaging the drive waveforms for driving the plurality of first LEDs.

  Here, the cumulative operation time includes a time during which the first LED 1 is not actually lit when the duty ratio of the drive waveform is not 100%. The average drive coefficient is determined when the first drive unit 5 drives each of the plurality of first LEDs 1 in the time from the previous integration process to the current integration process (hereinafter also referred to as “integration process interval”). The duty ratio of the drive waveform is averaged and shown individually. Specifically, for each of the plurality of first LEDs 1, assuming that the duty ratio of the drive waveform in the current integration process is constant in all PWM basic periods in the integration process interval, the average drive coefficient is as follows: Is calculated.

In the previous accumulation process, the 1LED display unit 10 is driven by the first drive unit 5, i.e. each of the plurality of first 1LED1 cumulative operation time that is driven by the first drive unit 5 and t _0, average driving factor Is R ₀ , the cumulative lighting time S ₀ of the first LED 1 is expressed by the following equation (1).

Then, in the current integration process, and the cumulative operation time t _1, the duty ratio of the drive waveform and R _1. Here, assuming that the duty ratio of the drive waveform is constant at R ₁ in all the PWM basic cycles during the integration processing interval from the cumulative operating time t ₀ to the cumulative operating time t ₁ , the cumulative operating time t ₁ cumulative lighting time S ₁ is represented by the following formula (2).

From the equations (1) and (2), the average drive coefficient R ₂ at the cumulative operation time t ₁ is expressed by the following equation (3).

The accumulating unit 6 calculates the average drive coefficient R ₂ at regular intervals from the time when the first LED display unit 10 is zero, that is, t ₀ = 0, and stores the average drive coefficient R ₂ in the lighting time storage unit 7. . Average drive coefficient R ₂ to be stored in the lighting time storage unit 7 is updated at regular time intervals.

When the change in the display pattern displayed by the first LED display unit 10 is small, that is, when the change in the luminance of the first LED 1 is small, the change in the duty ratio of the drive waveform for driving the first LED 1 is small. Therefore, even if the integration processing interval is set sufficiently long with respect to the PWM basic period, the cumulative lighting of the first LED 1 calculated from the actual lighting time of the first LED 1 and the average drive coefficient R ₂ stored in the lighting time storage unit 7 is achieved. error between the time _{S 1} is reduced. Therefore, it is possible to use the brightness correction processing described later the accumulated lighting time S _1. In this way, the integration processing amount can be reduced by increasing the integration processing interval with respect to the PWM basic cycle.

<Brightness reduction rate>
Next, the luminance reduction rate will be described. FIG. 3 is a diagram illustrating an example of the relationship between the cumulative lighting time and the luminance reduction rate in the first LED 1. In the example of FIG. 3, only the green (G) LED element 1a is shown. Further, the luminance reduction rate from the initial luminance is shown with the luminance when the cumulative lighting time is zero, that is, the initial luminance being 100%.

  As shown in FIG. 3, the luminance reduction rate of the green (G) LED element 1a increases as the cumulative lighting time increases. That is, the luminance of the green (G) LED element 1a decreases as the cumulative lighting time increases. Although FIG. 3 shows the luminance reduction rate of the green (G) LED element 1a, the luminance reduction rates of the red (R) and blue (B) LED elements 1a are similarly increased as the cumulative lighting time becomes longer. Increase (not shown).

  In the LED display device 100A according to the present embodiment, the luminance reduction rate of the first LED 1 is not calculated by prior measurement, but is calculated by measuring the luminance of the second LED 21 in real time by the luminance measurement unit 9. . Hereinafter, a method for measuring the luminance reduction rate will be described.

  The second LED display unit 20 is driven by the second drive unit 8 based on the drive data generated by the drive data generation unit 16. The duty ratio of the drive waveform in which the second drive unit 8 drives the second LED display unit 20 is 100%. Thereby, the cumulative lighting time of the second LED 21 becomes longer than the longest cumulative lighting time among the plurality of first LEDs 1. If the cumulative lighting time of the second LED 21 is longer than the cumulative lighting time of the first LED 1, the duty ratio of the drive waveform for driving the second LED 21 may be smaller than 100%.

  The luminance of the second LED 21 measured by the luminance measurement unit 9 is stored in the luminance reduction rate storage unit 11 as a luminance reduction rate associated with the cumulative lighting time of the second LED 21.

  FIG. 4 is a diagram illustrating an example of the relationship between the cumulative lighting time and the luminance reduction rate in the second LED 21. In the example of FIG. 4, the luminance decrease rates of the R, G, and B three-color LED elements 21 a in the second LED 21 are indicated by a short broken line, a solid line, and a long broken line, respectively.

  As shown in FIG. 4, the luminance reduction rate of the LED elements 21a of the three colors R, G, and B increases as the cumulative lighting time becomes longer. That is, the luminance of the R, G, and B color LED elements 21a decreases as the cumulative lighting time increases. Moreover, in the example of FIG. 4, the change of the brightness | luminance fall rate of the LED element 21a of 3 colors of R, G, and B is different, respectively.

  The luminance reduction rates of the three color LED elements 21a of R, G, and B are respectively shown as kr (t), kg (t), and kb (t) as a function of the cumulative lighting time t. FIG. 4 shows an example of the luminance decrease rates kr (trmax), kg (tgmax), and kb (tbmax) at the maximum cumulative lighting times trmax, tgmax, and tbmax of each of the LED elements 1a of three colors to be described later.

  By measuring the luminance of the three color LED elements 21a of R, G, and B by the luminance measuring unit 9, the luminance reduction rate with respect to the cumulative lighting time in each of the three color LED elements 21a can be measured in real time. Since the second LED 21 and the first LED 1 are the same LED, the luminance reduction rate of each of the three color LED elements 1a with respect to the cumulative lighting time in the first LED 1 is measured in real time by measuring the luminance reduction rate of the second LED 21. Will be doing. Thereby, the luminance reduction rate of the first LED 1 can be calculated with high accuracy.

<Operation of brightness correction processing>
Next, the brightness correction process will be described. FIG. 5 is a flowchart illustrating an example of the operation of the luminance correction processing of the LED display device 100A.

As shown in FIG. 5, first, in step ST <b> 1, the accumulating unit 6 calculates the maximum cumulative lighting time from the cumulative lighting time. Specifically, the integrating unit 6 calculates the R from the average driving coefficient R ₂ calculated for each of the three color LED elements 1a in each of the plurality of first LEDs 1, that is, all the LED elements 1a included in the first LED display unit 10. searches the average driving factor R ₂ of the maximum of each color of G and B, R, to calculate the maximum accumulated lighting time of each color of G and B.

  Next, in step ST2, the correction coefficient calculation unit 12 calculates the maximum luminance reduction rate. Specifically, the correction coefficient calculation unit 12 refers to the luminance decrease rate storage unit 11, and R, G, and B LEDs for each of the maximum accumulated lighting times of the R, G, and B colors calculated in step ST1. From the luminance reduction rate of the element 1a, the largest luminance reduction rate is selected, and the maximum luminance reduction rate is calculated.

  When the maximum cumulative lighting time for the LED elements 1a of R, G, and B colors is trmax, tgmax, and tbmax, respectively, the maximum luminance reduction is obtained from the luminance reduction rate functions kr (t), kg (t), and kb (t) The rate krgb (tmax) is expressed by the following formula (4).

  In the example of FIG. 4, the maximum cumulative lighting times trmax, tbmax, and tgmax are longer in that order, and the corresponding luminance reduction rates kr (trmax), kb (tbmax), and kg (tgmax) are in that order. The luminance reduction rate kr (trmax) at the maximum cumulative lighting time trmax of the R LED element 1a becomes the maximum luminance reduction rate krgb (tmax).

  Next, in step ST3, the correction coefficient calculation unit 12 calculates a correction coefficient for individually correcting the luminance of each of the plurality of first LEDs 1. Specifically, the correction coefficient calculation unit 12 refers to the lighting time storage unit 7 and the luminance reduction rate storage unit 11, and for all the first LEDs 1 provided in the first LED display unit 10, the luminance reduction with respect to the cumulative lighting time of the second LED 21. A correction coefficient for individually correcting the luminance of each of the plurality of first LEDs 1 is calculated from the rate and the maximum luminance reduction rate krgb (tmax) calculated in step ST2.

  Next, in step ST4, the brightness correction unit 4 individually corrects the brightness of each of the plurality of first LEDs 1. Specifically, the brightness correction unit 4 corrects the display data processed by the video signal processing circuit 3 with the correction coefficient calculated in step ST3, and individually corrects the brightness of each of the plurality of first LEDs 1. . The brightness correction unit 4 individually corrects the brightness of each of the plurality of first LEDs 1 by individually correcting the duty ratio of the drive waveform that drives each of the plurality of first LEDs 1 using a correction coefficient.

  The current luminances of the R, G, and B color LED elements 1a in the first LED 1 are Rp, Gp, and Bp, respectively, and the luminance reduction rate of each color LED element 1a during each cumulative lighting time t is kr (t), kg ( t) and kb (t), and the maximum luminance reduction rate is krgb (tmax), the corrected luminances Rcomp, Gcomp, and Bcomp of the LED elements 1a of the R, G, and B colors of the first LED 1 5).

  Rp, Gp, and Bp in the equation (5) are expressed as the following equation (6), where R0, G0, and B0 are the initial luminances of the R, G, and B LED elements 1a of the first LED 1 respectively. .

  Substituting equation (6) into equation (5), Rcomp, Gcomp, and Bcomp are given by equation (7) below.

  As shown in Equation (7), Rcomp, Gcomp, and Bcomp are uniformly corrected with respect to the respective initial luminances R0, G0, and B0 at the maximum luminance reduction rate krgb (tmax).

  Similarly to the luminance adjustment at the time of video display, the luminance can be corrected by changing the duty ratio of the drive waveform in the luminance correction. For example, for R LED element 1a, when krgb (tmax) = 0.2 and kr (t) = 0.1, the correction coefficient for Rp is (1-0. Since 2) / (1-0.1) = 8/9, the luminance can be corrected by multiplying the duty ratio of the PWM drive waveform by 8/9.

  Here, for example, in the monitoring application, the monitoring target becomes an abnormal state, and the LED display device 100A displays a warning video for notifying the user of the warning. In this case, the one or more first LEDs 1 display a portion that repeatedly blinks like a warning signal, which is a part of the warning video. The warning signal blinks at regular intervals, and the first LED 1 is regularly turned on and off repeatedly. The “flashing of the first LED 1” here is not the flashing (turning on / off) of the first LED 1 within the PWM basic period in PWM driving, but the change in the luminance of the first LED 1 at a period equal to or higher than the PWM basic period. This also applies to the following.

  FIG. 6 is a diagram illustrating a time relationship between blinking (lighting / extinguishing) of the first LED 1 and timing of integration processing performed by the integration unit 6.

  The uppermost waveform in FIG. 6 shows a change in the duty ratio of the first LED 1 that blinks at a constant cycle. In the example of FIG. 6, the duty ratio when the first LED 1 is turned on is 80%, and the duty ratio when the first LED 1 is turned off is 20%. Here, for convenience, the duty ratio at the time of extinction is set to 20% instead of 0% so that the calculation is easy to understand. Further, the blinking cycle of the first LED 1 is 4 seconds, and it is assumed that the LED elements 1a of the R, G, and B colors of the first LED 1 are all operating at the same duty ratio. In this way, the integration process as described above is performed on the first LED 1 blinking at a constant cycle, and the brightness correction process is performed.

  The waveforms shown in the second to fourth stages from the top in FIG. 6 indicate the timing of integration processing in integration processing (1) to (3) in which integration processing is performed at different timings, respectively. FIG. 7 is a diagram showing the time for each number of integration processes and the duty ratio of the drive waveform of the first LED 1 in each of the integration processes (1) to (3) shown in FIG.

  As shown in FIGS. 6 and 7, in the integration process (1), the cycle of the integration process is 2 seconds, which is half the blinking cycle of the first LED 1. For this reason, even when the first LED 1 is turned off from being turned on or vice versa, the integration process can be performed with good timing, so that the accumulated lighting time of each of the plurality of first LEDs 1 can be accurately measured. . In the example of FIGS. 6 and 7, the duty ratio of the first LED 1 is 80% during the odd-numbered integration process of the integration process (1), and is 20% during the even-numbered integration process. The integration process (2) and the integration process (3) will be described later in detail.

FIG. 8 shows the cumulative lighting time S ₀ , cumulative operating time t ₀ and average drive coefficient R ₀ in the previous integration process, and the current integration process for each integration process in the integration process (1) shown in FIGS. cumulative lighting time S ₁ in _the cumulative operating time t _1, a graph showing the calculation result of the duty ratio R ₁ and the average driving factor R ₂ of the drive waveform.

S ₀ , R ₀ , t ₀ , S ₁ , R ₁ , t ₁ and R ₂ are obtained for each LED element 1a of each color of the first LED ₁ , and krgb (tmax) is calculated from the equation (4). Luminance correction is performed from the calculated krgb (tmax) according to equation (7).

The value shown in FIG. 8 is assumed to be that of the LED element 1a which becomes krgb (tmax). As shown in FIG. 8, the average driving factor R ₂ of an integration process that is 16 seconds at 8 th in the integration process (1) it is 50%. Therefore, it can be seen that the maximum cumulative lighting time of the first LED ₁ is 8 seconds, which is 50% of the cumulative operating time t1. Here, since it is assumed that there is no difference in the duty ratio between the plurality of first LEDs 1, the description of the comparison of the maximum luminance reduction rate between the first LEDs 1 is omitted.

  FIG. 9 is a diagram illustrating the maximum cumulative lighting time and the luminance reduction rate in each of the integration processes (1) to (3). The graph of FIG. 9 represents the change in the luminance reduction rate with respect to the cumulative lighting time of the first LED 1. Originally, the data of the color with the highest luminance reduction rate should be shown, but the color is not specified for simplification.

A point A in FIG. 9 is a luminance reduction rate with respect to the maximum cumulative lighting time of the second LED 21. As shown in FIG. 8, since the cumulative lighting time S1 of the _first LED 1 in the integration process (1) is 8 seconds, the luminance reduction rate with respect to the maximum cumulative lighting time in the integration process (1) is point B in FIG. It becomes. A point C and a point D in FIG. 9 indicate the luminance decrease rate with respect to the maximum cumulative lighting time calculated in the integration process (2) and the integration process (3) described later, respectively.

  In the above description, it has been assumed that the integration process (1) can be performed in an ideal cycle, but in practice, the integration process is performed in the same cycle as the blinking cycle of the first LED 1. It is difficult in practice because of performance limitations. For this reason, the cycle of the integration process may be longer than the blinking cycle of the first LED 1.

  As shown in FIGS. 6 and 7, in the integration process (2), the integration process is performed at a cycle of 4 seconds longer than the blinking cycle of the first LED 1. In the examples of FIGS. 6 and 7, each integration process in the integration process (2) is performed when the duty ratio of the first LED 1 is 80%.

FIG. 10 shows the cumulative lighting time S ₀ , cumulative operating time t ₀ and average drive coefficient R ₀ in the previous integration process, and the current integration process for each integration process in the integration process (2) shown in FIGS. cumulative lighting time S ₁ in _the cumulative operating time t _1, a graph showing the calculation result of the duty ratio R ₁ and the average driving factor R ₂ of the drive waveform.

As shown in FIG. 10, 16 second time point in the integration process (2), i.e. the cumulative lighting time S ₁ at the time of fourth accumulation process is 12.8 seconds, 8 seconds in the integration process (1) It is longer than that. In other words, the correction coefficient calculation unit 12 recognizes that the first LED 1 has been lit for a longer time than the time that the first LED 1 was actually lit, and determines that the luminance has deteriorated due to aged deterioration over time. Therefore, at the time of brightness correction, the brightness of each first LED 1 is corrected more than necessary, and the entire first LED display unit 10 becomes darker than the actual power.

  In FIG. 9, a point C indicates a luminance reduction rate with respect to the maximum cumulative lighting time of the first LED 1 in the integration process (2). As shown in FIG. 9, the point C is at a point where the luminance is greatly reduced from the point B which is the ability of the first LED 1.

<Integration processing at random cycle>
As described above, when the integration process for calculating the cumulative lighting time S1 of the _first LED ₁ is performed at a constant period, the accuracy of luminance correction of the _first LED ₁ may be reduced. Therefore, in the present embodiment, the integration unit 6 performs integration processing at random time intervals, that is, random cycles, as shown in the integration processing (3) of FIGS. In the examples of FIGS. 6 and 7, the first, second, third, and fifth integration processes in the integration process (3) are performed when the duty ratio of the first LED 1 is 80%, and the fourth integration process is the first LED1. This is performed when the duty ratio is 20%.

FIG. 11 shows the cumulative lighting time S ₀ , cumulative operating time t ₀ and average drive coefficient R ₀ in the previous integration process, and the current integration process for each integration process in the integration process (3) shown in FIGS. cumulative lighting time S ₁ in _the cumulative operating time t _1, a graph showing the calculation result of the duty ratio R ₁ and the average driving factor R ₂ of the drive waveform.

As shown in FIG. 11, the accumulated lighting time _{S 1} in the integration process in the integration process (3) 16 second time point, that eighth in is 9.2 seconds, 12.8 seconds in the accumulation process (2) In comparison, the actual value is closer to 8 seconds in the integration process (1).

  In FIG. 9, a point indicating the luminance reduction rate with respect to the maximum cumulative lighting time of the first LED 1 by the integration process (3) is a point D. As shown in FIG. 9, the point D is closer to the point B than the point C, that is, the processing in the integration processing (3) is an integration value (1) that is an actual value than the processing in the integration processing (2). Therefore, the accuracy of brightness correction can be improved.

  As described above, when integration processing is performed at a fixed period, most of the content is still images and part of the content flashes at a fixed period, such as video content for monitoring purposes. The blinking cycle may coincide with the integration processing timing. In this case, inaccurate luminance correction may be performed by performing integration processing only when the first LED 1 is turned on or off. As a result, color misalignment and luminance misalignment between the plurality of first LEDs 1 may occur, or the video before switching may be displayed as an afterimage even when the display video is switched to a completely different video.

  On the other hand, in this Embodiment, since an integration process is performed with a random period, it can suppress that the blinking period of 1st LED1 and the timing of an integration process overlap. As a result, the accuracy of luminance correction of the first LED 1 can be improved.

  Moreover, since the brightness | luminance measurement part 9 measures the brightness | luminance of 2nd LED21 which is the same LED as 1st LED1, and measures the brightness | luminance reduction rate of 2nd LED21, compared with the case where a brightness | luminance reduction rate is measured beforehand. In addition, the accuracy of the luminance reduction rate can be improved. Therefore, more accurate luminance correction can be performed.

  In this embodiment, the method for randomly determining the period for performing the integration process is not specified, but random numbers are generated by a random function provided as a standard in the device or software, and the integration process is performed accordingly. May be. In addition, a plausible random number may be generated using a probability distribution function such as a Poisson distribution instead of a standard random function and used. Also in this case, in order to adjust the calculation amount of the integration process, the frequency of the integration process is set appropriately.

<Embodiment 2>
The period of the integration process may be registered in advance in the LED display device. However, when the blinking cycle existing in the video to be displayed is known in advance, it may be better to determine the integration processing cycle in accordance with the blinking cycle.

  FIG. 12 is a block diagram illustrating an example of the configuration of the LED display device 100B according to the second embodiment. As shown in FIG. 12, the LED display device 100B further includes an input unit 13 as compared with the LED display device 100A shown in FIG. In the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The user can input timing information indicating the timing of integration processing performed by the integration unit 6, that is, the cycle of integration processing, to the input unit 13. The integrating unit 6 can set the cycle of the integrating process based on the timing information input to the input unit 13.

  For example, an image in which the first LED 1 blinks is displayed as in the first embodiment, and the blinking cycle is also set to 4 seconds. If the user knows this blinking cycle, the timing of the integration process can be set in accordance with the blinking cycle.

  For example, when the blinking cycle of the first LED 1 is 4 seconds and the integration processing cycle is 3 seconds, the first to fourth integration processings are performed when the first LED 1 is off, on, on, and off, respectively. The integration processing is performed in synchronization with the blinking cycle of the first LED 1.

  Thus, when the blinking cycle of the first LED 1 is known in advance, the user can change the setting via the input unit 13 so that the integration unit 6 performs integration processing according to the cycle. . Thereby, the accuracy of luminance correction of the first LED 1 can be further improved by performing the integration process at a more appropriate cycle.

  Also in the present embodiment, when timing information is not input to the input unit 13, the integration unit 6 may perform integration processing at a random cycle.

<Embodiment 3>
When the video is blinking, the period is not always constant and may change with time. Also, the video content itself may change over time.

  When the timing and contents of these changes are known in advance, the user can improve the accuracy of luminance correction by setting the integration processing timing to change in time series.

  FIG. 13 is a diagram illustrating the relationship between the blinking of the first LED 1 and the timing of integration processing. In the example of FIG. 13, the blinking cycle of the first LED 1 is 2 seconds for 1 to 6 seconds, and the duty ratio is 80% when bright and 20% when dark. In addition, the blinking cycle of the first LED 1 is 4 seconds between 6 and 14 seconds, and the duty ratio is 60% or 40% when bright and 20% when dark. After 14 seconds, the blinking cycle of the first LED 1 is 2 seconds, and the duty ratio is 60% or 80% when bright and 20% when dark.

  Thus, when the blinking cycle of the first LED 1 changes with the passage of time, the integration process is not performed at a constant cycle, but the change in the blinking cycle of the first LED 1 as in the integration process (5) of FIG. It is preferable to change the cycle of the integration process according to the above.

  FIG. 14 is a block diagram illustrating an example of the configuration of the LED display device 100C according to the third embodiment. The LED display device 100C further includes a schedule management unit 14 as compared with the LED display device 100B according to the second embodiment shown in FIG. In the third embodiment, the same components as those described in the first and second embodiments are denoted by the same reference numerals and detailed description thereof is omitted.

  The user can input timing information indicating the timing of integration processing performed by the integration unit 6 to the input unit 13. In the present embodiment, the user can input the timing of integration processing that changes in time series as the timing information. The timing information is stored in the schedule management unit 14. The accumulating unit 6 can perform the integrating process while changing the period of the integrating process based on the timing that changes in time series indicated by the timing information recorded in the schedule managing unit 14.

  FIG. 15 is a diagram illustrating an example of timing information indicating the timing of integration processing that changes in time series stored in the schedule management unit 14. In FIG. 15, the upper part is the elapsed time, and the lower part is the period of the integration process. As shown in FIG. 15, the elapsed time is 0 to 6 seconds and the period of the integration process is registered as 1 second, and the integration unit 6 performs the integration process at the 1 second period for 0 to 6 seconds. . Similarly, integration processing is performed at a cycle of 2 seconds for 6 to 14 seconds, and integration processing is performed at a cycle of 1 second after 14 seconds. As described above, the integration unit 6 performs the integration process in synchronization with the blinking cycle of the first LED 1 at the timing shown in the integration process (5) of FIG. 13 based on the schedule shown in FIG.

  As described above, when the change of the video and the timing thereof are known in advance, if the user registers the period of integration processing that changes in time series in accordance with them in the schedule management unit 14, the timing is optimal. Integration processing can be performed, and the accuracy of luminance correction can be improved.

  Also in the present embodiment, when timing information is not input to the input unit 13, the integration unit 6 may perform integration processing at a random cycle.

<Embodiment 4>
In a monitoring application, a warning video blinking at a predetermined cycle is displayed in an emergency, but a warning video may not be displayed in a normal time other than an emergency. In that case, it is desirable to change the timing of the integration processing in accordance with the operating state of the LED display device. Hereinafter, an operation mode of the LED display device in which a warning image is displayed on the LED display unit and the LED of the LED display unit flashes at a predetermined cycle is referred to as a “flashing mode”, and an operation mode other than the flashing mode is referred to as “ This is called “normal mode”.

  In order to switch the timing of integration processing according to the operation mode of the LED display device, the timing of integration processing for each operation mode is stored in advance in the LED display device. For the blink mode, the timing of the integration process suitable when the LED is blinking at a predetermined cycle is registered. On the other hand, for the normal mode, the timing of integration processing different from that for the blinking mode is registered.

  FIG. 16 is a block diagram illustrating an example of the configuration of the LED display device 100D according to the fourth embodiment. The LED display device 100D further includes a mode management unit 15 as compared with the LED display device 100B according to the second embodiment shown in FIG. In the fourth embodiment, the same components as those described in the first and second embodiments are denoted by the same reference numerals and detailed description thereof is omitted.

  The user can input timing information indicating the timing of integration processing performed by the integration unit 6 to the input unit 13 in association with each mode. The timing information is stored in the mode management unit 15. The mode management unit 15 determines the operation mode of the LED display device 100D, and outputs timing information associated with the determined operation mode to the integration unit 6 based on the determination result. The integration unit 6 performs integration processing based on the timing indicated by the timing information output from the mode management unit 15.

  For example, the case where the first LED 1 blinks at a cycle of 2 seconds is set as a blinking mode, and the other case is set as a normal mode. The mode management unit 15 registers timing information of integration processing at a 1-second cycle for the blink mode. In addition, it is assumed that timing information for performing the integration process at a cycle of 2 seconds is registered for the normal mode.

  In this case, the mode management unit 15 determines whether or not the operation mode of the LED display device 100D is the flashing mode. When determining that the LED display device 100D is the flashing mode, the mode management unit 15 has a cycle of 1 second associated with the flashing mode. Is output to the integrating unit 6. In this case, the integration unit 6 performs integration processing at the timing indicated by the timing information output from the mode management unit 15, that is, at a cycle of 1 second.

  On the other hand, when the mode management unit 15 determines that the operation mode of the LED display device 100D is not the blinking mode, that is, the normal mode, the mode management unit 15 displays the timing information of the integration process in a cycle of 2 seconds associated with the normal mode. The result is output to the integrating unit 6. In this case, the integration unit 6 performs integration processing at the timing indicated by the timing information output from the mode management unit 15, that is, at a cycle of 2 seconds.

  As described above, when the first LED 1 blinks as shown in the upper part of FIG. 13, even if the integration process is performed by switching the timing of the integration process according to the operation mode, the integration process (5 ) Is obtained. Specifically, the integration process is performed in the blinking mode period from 0 to 6 seconds in the integration process (5) of FIG. For 6 to 14 seconds, integration processing is performed in the cycle of the normal mode. After 14 seconds, the integration process is performed again with the cycle of the blinking mode.

  As described above, even when the integration process is performed at the timing corresponding to the operation mode of the LED display device stored in the mode management unit 15, at least the same effect as in the third embodiment can be obtained, and the integration is performed at a constant cycle. The accuracy of luminance correction can be improved as compared with the case where processing is performed.

  Also in the present embodiment, when timing information is not input to the input unit 13, the integration unit 6 may perform integration processing at a random cycle.

<Hardware configuration of LED display device>
FIG. 17 is a block diagram illustrating an example of a hardware configuration of the LED display device 200 that can be used as any one of the LED display devices 100A to 100D described above. As shown in FIG. 17, the LED display device 200 includes an input interface 201, a processing circuit 202, a first drive circuit 203, a first display device 204, a storage device 205, a memory 206, a luminance measurement device 207, and a second drive circuit. 208 and a second display device 209. These components are connected to each other via a bus 210.

  The input terminal 2 and the input unit 13 are realized by the input interface 201. The luminance measuring unit 9 is realized by the luminance measuring device 207.

  The first LED display unit 10 and the second LED display unit 20 correspond to the first display device 204 and the second display device 209, respectively. The first drive unit 5 and the second drive unit 8 correspond to the first drive circuit 203 and the second drive circuit 208, respectively.

  The lighting time storage unit 7 and the luminance decrease rate storage unit 11 are realized by the storage device 205. The storage device 205 is, for example, a nonvolatile memory.

  The functions of the video signal processing circuit 3, the luminance correction unit 4, the integration unit 6, the correction coefficient calculation unit 12, the drive data generation unit 16, the schedule management unit 14, and the mode management unit 15 are realized by the processing circuit 202. The processing circuit 202 may be dedicated hardware, or a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, processor that executes a program stored in the memory 206 (Also referred to as DSP).

  When the processing circuit 202 is dedicated hardware, the processing circuit 202 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. . A processing circuit in which the functions of the video signal processing circuit 3, the luminance correction unit 4, the integration unit 6, the correction coefficient calculation unit 12, the drive data generation unit 16, the schedule management unit 14, and the mode management unit 15 are individually provided. It may be realized, or the functions of the respective units may be realized by a single processing circuit 202.

  When the processing circuit 202 is a CPU, each function of the video signal processing circuit 3, the luminance correction unit 4, the integration unit 6, the correction coefficient calculation unit 12, the drive data generation unit 16, the schedule management unit 14, and the mode management unit 15 is It is realized by software, firmware, or a combination of software and firmware. Software and firmware are described as programs and stored in the memory 206. The processing circuit 202 implements the functions of each unit by reading and executing the program stored in the memory 206. In addition, these programs are computerized procedures and methods of the video signal processing circuit 3, the luminance correction unit 4, the integration unit 6, the correction coefficient calculation unit 12, the drive data generation unit 16, the schedule management unit 14, and the mode management unit 15. It can be said that this is what is executed. Here, the memory 206 is, for example, a nonvolatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM, an EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, or the like. Applicable.

  Note that some of the functions of the video signal processing circuit 3, the luminance correction unit 4, the integration unit 6, the correction coefficient calculation unit 12, the drive data generation unit 16, the schedule management unit 14, and the mode management unit 15 are partially dedicated hardware. It may be realized by hardware and a part may be realized by software or firmware. As described above, the processing circuit 202 can realize the above-described functions by hardware, software, firmware, or a combination thereof.

  In each of the above examples, the case where the first LED 1 and the second LED 21 are full-color LEDs has been described. However, the first LED 1 and the second LED 21 have other configurations such as a single-color display LED including only one LED element. LED may be used.

  In the scope of the present invention, the embodiments can be freely combined, or the embodiments can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 1st LED, 1a, 21a LED element, 2 input terminal, 3 video signal processing circuit, 4 brightness correction part, 5 1st drive part, 6 integrating | accumulating part, 7 lighting time memory | storage part, 8 2nd drive part, 9 brightness measurement Unit, 10 first LED display unit, 11 brightness reduction rate storage unit, 12 correction coefficient calculation unit, 13 input unit, 14 schedule management unit, 15 mode management unit, 16 drive data generation unit, 20 second LED display unit, 21 second LED , 100A to 100D, 200 LED display device, 201 input interface, 202 processing circuit, 203 first driving circuit, 204 first display device, 205 storage device, 206 memory, 207 luminance measuring device, 208 second driving circuit, 209 first 2 display devices, 210 buses.

Claims (7)

An LED display device comprising: an LED display unit having each of a plurality of LEDs as pixels; and a drive unit that drives the LED display unit based on input display data,
An integration unit that calculates an accumulated lighting time obtained by individually integrating the lighting times of each of the plurality of LEDs at random time intervals;
An LED display device comprising: a luminance correction unit that individually corrects the luminance of each of the plurality of LEDs based on the cumulative lighting time of each of the plurality of LEDs calculated by the integration unit. The LED display device according to claim 1,
The integrating unit calculates a cumulative driving time in which the LED display unit is driven by the driving unit at random time intervals, and the driving unit drives the LED display unit based on a current driving condition. An average drive coefficient for each of the LEDs is calculated by individually averaging the ratio of the lighting time to the cumulative operating time, and the cumulative lighting time of each of the plurality of LEDs is calculated based on the cumulative driving time and the average driving coefficient. LED display device to calculate. The LED display device according to claim 1 or 2,
The LED, the LED display unit, and the drive unit are a first LED, a first LED display unit, and a first drive unit, respectively.
The LED display device
A second LED display unit having a second LED that is the same LED as the first LED;
A second drive unit that drives the second LED display unit such that a cumulative lighting time of the second LED is longer than a cumulative lighting time of each of the plurality of first LEDs;
A brightness measuring unit for measuring the brightness of the second LED;
In the luminance correction unit, the cumulative lighting time of each of the plurality of first LEDs calculated by the integrating unit and the luminance of the second LED measured by the luminance measuring unit are associated with the cumulative lighting time of the second LED. An LED display device that individually corrects the brightness of each of the plurality of first LEDs based on the brightness reduction rate. The LED display device according to any one of claims 1 to 3,
The LED is a first LED,
The LED display device
An input unit to which timing information indicating a timing at which the integration unit calculates a cumulative lighting time of each of the plurality of first LEDs is input;
The accumulation unit calculates an accumulated lighting time of each of the plurality of first LEDs at the timing indicated by the timing information input to the input unit. The LED display device according to claim 4,
The LED display device, wherein the timing information is information indicating the timing changing in time series. The LED display device according to claim 4,
A plurality of operation modes including a blinking mode in which the first LED blinks at a predetermined period;
A mode management unit for determining whether the operation mode of the LED display device is the flashing mode;
The timing information is information indicating a plurality of the timings associated with each of the plurality of operation modes,
When the operation mode of the LED display device is determined to be the blinking mode by the mode management unit, the integrating unit is configured to perform the first LED at the timing associated with the blinking mode indicated by the timing information. LED display device that calculates the cumulative lighting time of each. A brightness correction method for an LED display device comprising: an LED display unit having each of a plurality of LEDs as a pixel; and a drive unit that drives the LED display unit based on input display data,
(A) calculating a cumulative lighting time obtained by individually integrating lighting times of the plurality of LEDs at random time intervals;
(B) A luminance correction method for an LED display device, comprising: individually correcting the luminance of each of the plurality of LEDs based on the cumulative lighting time of each of the plurality of LEDs calculated in the step (a).

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