JP2017032890A - LED display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of suppressing luminance variation and color variation of a first LED display while a desired image is being displayed on a first LED display.SOLUTION: An LED display device 100 includes: a first LED display 1 having a first LED 1a; a second LED display 2 having a second LED 2a; and a luminance correction part 18. The luminance correction part 18 corrects the luminance of the first LED 1a on the basis of a first cumulative lighting time of the first LED 1a and a luminance change and a second cumulative lighting time of the second LED 2a.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an LED display device including an LED display unit having an LED (Light Emitting Diode).

  LED display devices having LEDs are used in many applications such as outdoor and indoor advertising displays due to the technological development and cost reduction of LEDs. Specifically, conventionally, LED display devices have been mainly used for displaying natural images and moving images of animation. However, in recent years, with the narrowing of the pixel pitch, it has become possible to maintain the image quality even when the viewing distance is short. Therefore, it is also used indoors as a conference room and a monitoring application.

  Of these, in surveillance applications, a personal computer image close to a still image is often displayed. However, since the luminance of the LED decreases as the lighting time becomes longer, the lighting time of each LED, and hence the luminance decrease rate of each LED, differs depending on the content of the image. As a result, the luminance variation and color variation of the pixels with the lighting time occurred.

  In order to reduce such luminance variation and color variation, a technique for detecting the luminance of the LED display unit and correcting the luminance, or integrating the display time of the LED, and based on the integrated time obtained by the integration. Techniques have been proposed for correcting the luminance by correcting the luminance correction coefficient (for example, Patent Documents 1 and 2).

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

  According to the technology that measures the brightness decrease rate of the LED based on the accumulated time by a life test and corrects the brightness using the brightness decrease rate, the brightness variation and the color variation caused by the difference in the lighting time of the LED are corrected. It is possible to do. However, there are inevitably variations in characteristics that are difficult to predict, such as variations in characteristics due to differences in LED production lots. For this reason, it has been difficult to accurately correct luminance variations based simply on the integration time.

  Further, in the technique of detecting the luminance from the LED display unit that displays a desired image, it is possible to correct the luminance with high accuracy, but it is necessary to display an image for luminance detection when detecting the luminance. For this reason, in a display system that requires operation for 24 hours (for example, the above-described display system for monitoring use), the display (operation) is stopped to correct the luminance variation or the like, or the luminance variation is maintained to maintain the display. I had to accept one of the abandonment of the correction.

  Therefore, the present invention has been made in view of the above problems, and can suppress luminance variation and color variation of the first LED display unit while displaying a desired image on the first LED display unit. The purpose is to provide technology.

  The LED display device according to the present invention includes a first LED display unit having a first LED, a second LED display unit having a second LED having a luminance transition equivalent to that of the first LED, and a first cumulative lighting time of the first LED. A lighting time storage unit for storing; a luminance measuring unit for measuring the luminance of the second LED; a transition of the luminance of the second LED measured by the luminance measuring unit; and a second cumulative lighting time of the second LED. The luminance transition storage unit that stores the associated information, the first cumulative lighting time stored in the lighting time storage unit, the luminance transition and the second cumulative of the second LED stored in the luminance transition storage unit And a luminance correction unit that corrects the luminance of the first LED based on the lighting time.

  According to the present invention, based on the first cumulative lighting time stored in the lighting time storage unit, the luminance transition of the second LED stored in the luminance transition storage unit, and the second cumulative lighting time, the first LED display unit The brightness of the first LED is corrected. Thereby, the brightness variation and color variation of the first LED display unit can be suppressed while a desired image is displayed on the first LED display unit.

1 is a block diagram illustrating a configuration of an LED display device according to Embodiment 1. FIG. 3 is a block diagram showing a hardware configuration of the LED display device according to Embodiment 1. FIG. It is a figure which shows an example of the relationship between the lighting time of 1st LED, and a luminance fall rate. It is a figure which shows an example of the relationship between the lighting time of 2nd LED, and a luminance fall rate. 3 is a flowchart showing the operation of the LED display device according to Embodiment 1. It is a figure which shows an example of PWM drive.

<Embodiment 1>
FIG. 1 is a block diagram showing a configuration of an LED display device according to Embodiment 1 of the present invention. The LED display device 100 of FIG. 1A includes a first LED display unit 1, a second LED display unit 2, an input terminal 3, a video signal processing unit 4, a signal correction unit 5, and a first drive unit 6. A lighting time storage unit 7, a signal generation unit 8, a second drive unit 9, a luminance measurement unit 10, a luminance decrease rate storage unit 11 as a luminance transition storage unit, and a correction coefficient calculation unit 12. Note that the luminance correction unit 18 includes a signal correction unit 5 and a correction coefficient calculation unit 12.

  First, the hardware of each component will be described. For example, an LED display panel is applied to the first LED display unit 1 and the second LED display unit 2, and a measurement device such as a photodiode capable of measuring at a wavelength in the visible range is applied to the luminance measurement unit 10, for example. . For example, the memory 91 of FIG. 2 is applied to the lighting time storage unit 7 and the luminance decrease rate storage unit 11. The video signal processing unit 4, the signal correction unit 5, the first drive unit 6, the signal generation unit 8, the second drive unit 9, and the correction coefficient calculation unit 12 (hereinafter referred to as “video signal processing unit 4 etc.”) For example, the processor 92 in FIG. 2 is realized by executing a program stored in the memory 91.

  The memory 91 includes, for example, a nonvolatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM, and an EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, and a DVD. The processor 92 includes, for example, a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, and a DSP. The program causes a computer to execute procedures and methods such as the video signal processing unit 4 and is realized by, for example, software, firmware, or a combination of software and firmware.

  Note that the video signal processing unit 4 and the like are not limited to a configuration realized by operating according to a software program, and may be, for example, a signal processing circuit that realizes the operation with a hardware electric circuit. Alternatively, the video signal processing unit 4 or the like may be a combination of a configuration realized by a software program and a configuration realized by hardware.

  Next, after describing the outline | summary of each component of the LED display apparatus 100 of FIG. 1, some components are demonstrated in detail.

<Overview>
The 1st LED display part 1 is used in order to display desired images, such as a character and a figure, for example. The first LED display unit 1 includes a plurality of first LEDs 1a, and is driven based on a first drive signal (in other words, a display pattern, a drive pattern, drive data) from the first drive unit 6, Lighting control of each first LED 1a is performed.

  The first LED 1a includes any one of red (R), green (G), and blue (B) LEDs, and the plurality of first LEDs 1a included in the first LED display unit 1 includes R, G, and B LEDs. It is out. In the example shown in FIG. 1A, a total of 16 sets of first LEDs 1a of 4 sets x 4 sets are arranged in a matrix. And 1 set of 1st LED1a contains a total of three LED of R, G, and B, as shown in FIG.1 (b). However, the number of 1st LED1a is not restricted to this.

  The second LED display unit 2 performs display for measuring (predicting) the transition of the luminance of the first LED display unit 1. Note that the transition of the luminance is, for example, a luminance maintenance rate indicating the current luminance when the initial luminance is 100%, or a luminance reduction rate that is inversely related to the luminance maintenance rate (= 100% −luminance maintenance rate). Etc. In the following description, it is assumed that the luminance decrease rate is applied to the luminance transition.

  The second LED display unit 2 includes a plurality of second LEDs 2a, and is driven based on a second drive signal (in other words, a display pattern, a drive pattern, drive data) from the second drive unit 9, Lighting control of each second LED 2a is performed.

  Here, the luminance reduction rate of the second LED 2a is equal to the luminance reduction rate of the first LED 1a. That is, the brightness reduction rate of the second LED 2a is the same as or similar to the brightness reduction rate of the first LED 1a. For example, when an LED having the same manufacturing lot is applied to the first LED 1a and the second LED 2a, or an LED having the same BIN code for classifying the LED according to the luminance and the wavelength is applied, the characteristics such as the luminance and the wavelength of both are matched. Therefore, the luminance reduction rate of both is equal.

  Similarly to the first LED 1a, the second LED 2a includes one of R, G, and B LEDs, and the plurality of second LEDs 2a included in the second LED display unit 2 include R, G, and B LEDs. In the example of FIG. 1A, a total of four sets of second LEDs 2a of 2 sets in length × 2 sets in width are arranged in a matrix. And 1 set of 2nd LED2a contains total 3 LED of R, G, and B like 1 set of 1st LED1a. However, the number of 2nd LED2a is not restricted to this.

  In addition, in the first embodiment, display (drive) of the first LED display unit 1 and display (drive) of the second LED display unit 2 are performed in parallel. Thereby, since 1st LED1a and 2nd LED2a are lighted on in the same environment, it is possible to make both luminance fall rates mutually close.

  The input terminal 3 receives a video signal from the outside. The video signal processing unit 4 selects an area necessary for display based on the video signal received at the input terminal 3 and performs processing such as gamma correction.

  The signal correction unit 5 corrects the luminance of the output signal of the video signal processing unit 4 using a correction coefficient from the correction coefficient calculation unit 12 described later. By this correction, the signal correction unit 5 can substantially correct the first drive signal from the first drive unit 6 to the first LED display unit 1, and consequently the luminance of one or more first LEDs 1a. .

  The first drive unit 6 generates a first drive signal for driving the first LED display unit 1 based on the output signal corrected by the signal correction unit 5. The first drive unit 6 drives the first LED display unit 1 by outputting the first drive signal to the first LED display unit 1.

  The lighting time storage unit 7 stores the first cumulative lighting time of the first LED 1a (the time obtained by cumulatively adding the time when the first LED 1a is turned on).

  The signal generation unit 8 generates a signal for generating a second drive signal for the second LED display unit 2 based on the output signal corrected by the signal correction unit 5.

  The second drive unit 9 generates a second drive signal for driving the second LED display unit 2 based on the signal generated by the signal generation unit 8. The second drive unit 9 drives the second LED display unit 2 by outputting the second drive signal to the second LED display unit 2.

  The luminance measuring unit 10 measures the luminance of the second LED 2a of the second LED display unit 2.

  The luminance decrease rate storage unit 11 which is a luminance transition storage unit is a cumulative representation of the luminance decrease rate of the second LED 2a measured by the luminance measurement unit 10 and the second cumulative lighting time of the second LED 2a (the time when the second LED 2a was lit). Is stored in association with the time obtained by adding to. In addition, the measurement of the brightness | luminance measurement part 10 and the memory | storage of the brightness | luminance fall rate memory | storage part 11 are performed at any time while the 2nd LED display part 2 is displayed.

  The correction coefficient calculation unit 12 is based on the first cumulative lighting time stored in the lighting time storage unit 7, the luminance reduction rate of the second LED 2a and the second cumulative lighting time stored in the luminance reduction rate storage unit 11. A luminance correction coefficient is calculated.

  Here, the luminance correction unit 18 of FIG. 1 includes the signal correction unit 5 and the correction coefficient calculation unit 12 described above. For this reason, the luminance correction unit 18 is based on the first cumulative lighting time stored in the lighting time storage unit 7 and the luminance reduction rate and second cumulative lighting time of the second LED 2a stored in the luminance reduction rate storage unit 11. To calculate the correction coefficient described above. Then, the luminance correction unit 18 corrects the luminance of the output signal of the video signal processing unit 4 using the correction coefficient, whereby the first driving signal (driving signal) of the first driving unit 6 and eventually the first LED 1a. Correct the brightness.

  In the first embodiment, the plurality of first cumulative lighting times of the plurality of first LEDs 1a are different. Then, the luminance correction unit 18 has the longest first cumulative lighting time among the plurality of first cumulative lighting times stored in the lighting time storage unit 7 and the luminance reduction of the second LED 2 a stored in the luminance reduction rate storage unit 11. The correction is performed based on the rate and the second cumulative lighting time.

<Details>
In the first embodiment, information on the duty ratio of the first drive signal of the first drive unit 6 is included in the output signal corrected by the signal correction unit 5. The lighting time storage unit 7 stores the first cumulative lighting time of each of the first LEDs 1a by accumulating the lighting time of each of the first LEDs 1a every certain unit time based on the duty ratio included in the output signal. To do. For example, when the unit time is 1 hour and the lighting is a luminance with a duty ratio of 10%, the lighting time of 0.1 hour (time excluding the turn-off time from the blinking time) is 1 hour. , And is added to the first cumulative lighting time of the lighting time storage unit 7.

  FIG. 3 is a diagram illustrating an example of the relationship between the luminance reduction rate of the first green LED 1a and the lighting time (first cumulative lighting time). In addition, the logarithmic scale is applied to the scale of the lighting time of FIG.

  As shown in FIG. 3, as the lighting time increases, the luminance reduction rate of the green (G) first LED 1a increases, and the luminance of the green (G) first LED 1a decreases. Although there is a difference in degree, the luminance of the red (R) and blue (B) first LEDs 1a also decreases as the lighting time increases (not shown). As will be described later, the luminance of the second LED 2a also decreases as the lighting time increases.

  In the prior art, the luminance reduction rate of the first LED 1a is obtained by actually measuring the luminance in advance. On the other hand, in Embodiment 1, instead of actually measuring the luminance of the first LED 1a, the first lighting time is actually measured and associated with the second lighting time that is substantially the same as the first lighting time. The luminance reduction rate of the second LED 2a is measured (predicted) as the luminance reduction rate of the first LED 1a. Hereinafter, measurement (prediction) of the luminance reduction rate of the first LED 1a will be described.

  Based on the output signal corrected by the signal correction unit 5, the signal generation unit 8 generates a signal serving as a second drive signal for controlling the display of the second LED display unit 2. The second drive unit 9 drives the second LED display unit 2 based on the signal generated by the signal generation unit 8.

  Here, the signal generation unit 8 reads the maximum duty ratio of the first drive signal (for example, a PWM (Pulse Width Modulation) signal) of the first LED display unit 1 from the output signal corrected by the signal correction unit 5, and the maximum A signal for driving the second LED display unit 2 with the duty ratio is generated. Thereby, if the maximum duty ratio of the first drive signal of the first LED display unit 1 is 100%, the duty ratio of the second drive signal of the second LED display unit 2 is also set to 100%.

  As a result, in the first embodiment, the second cumulative lighting time of the second LED 2a is set to the longest first cumulative lighting time among the first cumulative lighting times of the plurality of first LEDs 1a included in the first LED display unit 1. The That is, the length of the second cumulative lighting time of the second LED 2a is controlled to be equal to or longer than the length of the first cumulative lighting time of the first LED 1a. This control may be performed for each of R, G, and B.

  The luminance measuring unit 10 is disposed to face the second LED display unit 2 and measures the luminance of the second LED 2a. In Embodiment 1, the brightness | luminance measurement part 10 measures the brightness | luminance of each color of each 2nd LED2a.

  FIG. 4 is a diagram illustrating an example of the relationship between the luminance decrease rate of the second LEDs 2a of R, G, and B and the lighting time (second cumulative lighting time) that is an elapsed time. In addition, the logarithmic scale is applied to the scale of the lighting time of FIG.

  As FIG. 4 shows, the brightness | luminance of 2nd LED2a also falls with lighting time similarly to the brightness | luminance of 1st LED1a. Here, the luminance reduction rates of the second LEDs 2a of R, G, and B can be indicated by functions kr (t), kg (t), and kb (t) of the lighting time t, respectively. The functions kr (t), kg (t), and kb (t) are used to perform regression analysis or the like on the luminance reduction rate and the second cumulative lighting time of the plurality of sets of second LEDs 2a stored in the luminance reduction rate storage unit 11. Can be calculated as a relational expression such as an approximate expression or an interpolation expression.

  In the luminance reduction rate storage unit 11, the measurement result of the luminance measurement unit 10 and the lighting time of the second LED 2a are stored in association with each other. Then, the luminance correction unit 18 reads the luminance (luminance reduction rate) corresponding to the lighting time of the second LED 2a that is the same as or close to the lighting time (actual measurement time) of the first LED 1a stored in the lighting time storage unit 7. Thereby, in this Embodiment 1, even if it does not measure the brightness | luminance of 1st LED1a, it is possible to measure the brightness | luminance fall rate of 1st LED1a substantially.

<Operation>
FIG. 5 is a flowchart showing the brightness correction operation of the LED display device 100 according to the first embodiment.

  First, in step S1, the luminance correction unit 18 (the signal correction unit 5 and the correction coefficient calculation unit 12) determines whether the time from the start of operation or the previous correction to the current time is a unit time for luminance correction (for example, 100 hours). ) Is exceeded. Here, the unit time for luminance correction may be a fixed time, or may be a time that varies depending on the number of corrections (for example, a time indicated as an exponential function of the number of corrections). If it is determined that the unit time for luminance correction has elapsed, the process proceeds to step S2, and if not, step S1 is performed again.

  In step S2, the luminance correction unit 18 refers to the lighting time storage unit 7 and searches for the maximum cumulative lighting time trmax, tgmax, tbmax of the first LED 1a of R, G, B.

  In step S3, the luminance correction unit 18 calculates the R, G, and B luminance decrease rates corresponding to the second cumulative lighting time that is the same as or close to the maximum cumulative lighting time trmax, tgmax, and tbmax searched in step S2. Obtained from the decrease rate storage unit 11. The brightness reduction rates of R, G, and B acquired here are obtained by applying trmax, tgmax, and tbmax to t of the function kr (t), kg (t), and kb (t) of the brightness reduction rate described above, respectively. It is almost the same as kr (trmax), kg (tgmax), and kb (tbmax). Therefore, in the following description, for the sake of convenience, the luminance reduction rates of R, G, and B acquired in step S3 are sometimes referred to as luminance reduction rates kr (trmax), kg (tgmax), and kb (tbmax).

  The luminance correction unit 18 obtains the largest luminance reduction rate among the luminance reduction rates kr (trmax), kg (tgmax), and kb (tbmax) as the maximum luminance reduction rate krgb (tmax). That is, the luminance correction unit 18 obtains the maximum luminance reduction rate krgb (tmax) expressed by the following equation (1).

  In step S4, the luminance correction unit 18 refers to the lighting time storage unit 7 and the luminance reduction rate storage unit 11, and the theoretical luminance reduction rate with respect to the cumulative lighting time t for all the first LEDs 1a of the first LED display unit 1. Based on the maximum luminance reduction rate krgb (tmax) obtained in step S3, a correction coefficient for each first LED 1a is obtained.

  Here, the current theoretical brightness of the first LED 1a of R, G, B is Rp, Gp, Bp, and the theoretical brightness decrease rate of the first LED 1a of R, G, B during the cumulative lighting time t is kr (t ), Kg (t), kb (t) and the maximum luminance reduction rate is krgb (tmax), the corrected luminances Rcomp, Gcomp, Bcomp of the first LED 1a of R, G, B are given by the following equation (2): Indicated by For example, the maximum luminance reduction rate obtained in the previous correction is applied to the R, G, and B luminance reduction rates kr (t), kg (t), and kb (t) in the cumulative lighting time t.

  The brightness correction unit 18 according to the first embodiment uses an expression obtained by removing Rp, Gp, and Bp from the expression on the right side of the above expression (2) as an expression for the correction coefficient to be obtained in step S4.

  The current theoretical brightness Rp, Gp, Bp in the above formula (2) is represented by the following formula (3), assuming that the initial brightness of the first LEDs 1a of R, G, B is R0, G0, B0.

  If the above equation (3) is substituted into the above equation (2), the corrected luminances Rcomp, Gcomp, and Bcomp of the first LEDs 1a of R, G, and B are expressed by the following equation (4). As shown in the following equation (4), the luminances Rcomp, Gcomp, and Bcomp are uniformly corrected for the initial luminances R0, G0, and B0 of the first LEDs 1a of R, G, and B by the maximum luminance reduction rate krgb (tmax). Will be.

  After step S4, in step S5, the luminance correction unit 18 substantially corrects the luminance of the output signal of the video signal processing unit 4 and substantially the first drive signal using the correction coefficient obtained in step S4. Thus, the luminance of the first LED 1a is corrected. Then, it returns to step S1.

  Here, for example, a PWM method or the like is applied to the luminance adjustment of the first LED 1a. FIG. 6 is a diagram illustrating an example of PWM driving used in the PWM method. FIG. 6A shows a basic period (pulse period) of PWM, and a period of one frame period or less of the video signal is applied to the basic period of PWM. FIG. 6B shows a case where the duty ratio of the pulse width is 85%, for example, and FIG. 6C shows a case where the duty ratio of the pulse width is 80%, for example. Since the pulse period is very short, blinking of the LED of the pulse period is perceived as lighting by human eyes. In such a PWM method, the smaller the duty ratio is, the smaller the LED lighting time ratio is. Therefore, the luminance perceived by human eyes is lower in the case of FIG. 6C than in the case of FIG. 6B. Become. Thus, the luminance of the first LED 1a can be adjusted by changing the duty ratio of the pulse width.

  In step S5 described above, the luminance is corrected by changing the duty ratio of the pulse width as in the luminance adjustment. For example, in the case of krgb (tmax) = 0.2 and kr (t) = 0.1, the luminance is calculated by the correction coefficient formula (the formula on the right side of the above formula (2) excluding Rp, Gp, Bp). The correction coefficient for Rp is (1-0.2) / (1-0.1) = 8/9. For this reason, the luminance correction unit 18 corrects the first LED 1a by multiplying the PWM duty ratio by 8/9.

<Summary of Embodiment 1>
According to the LED display device 100 according to the first embodiment that performs the correction as described above, the luminance after correction of the first LED display unit 1 is reduced as a whole as compared with the luminance before correction. The brightness | luminance of 1st LED1a can be unified to the brightness | luminance (luminance with the largest brightness | luminance fall rate) of LED with the longest lighting time. For this reason, brightness uniformity and white balance can be maintained as a whole of the first LED display unit 1, and brightness variations and color variations can be suppressed.

  In the first embodiment, the second LED display unit 2 is driven at the maximum duty ratio of the first LED display unit 1. Thereby, since the length of the 2nd cumulative lighting time of 2nd LED2a becomes more than the length of the 1st cumulative lighting time of 1st LED1a, the brightness | luminance fall of 2nd LED2a is the same as the brightness fall of 1st LED1a or more than it Get faster. This means that the luminance reduction rate storage unit 11 stores the luminance reduction rate of the second LED 2a having the longest lighting time as the future luminance reduction rate of the first LED 1a. In Embodiment 1, since the luminance reduction rate of the first LED 1a is predicted based on the luminance reduction rate of the second LED 2a stored in the luminance reduction rate storage unit 11, the prediction accuracy of the luminance reduction rate of the first LED 1a, and consequently The accuracy of brightness correction can be increased.

  In the prior art, the luminance reduction rate of the first LED display unit 1 cannot be measured while a desired image is continuously displayed on the first LED display unit 1, and luminance variations and color variations can be suppressed. There wasn't. On the other hand, in the first embodiment, by measuring the luminance reduction rate of the second LED display unit 2 different from the first LED display unit 1 while displaying a desired image on the first LED display unit 1. Since the luminance reduction rate of the first LED display unit 1 can be substantially measured, it is possible to suppress luminance variations and color variations. As a result, a reduction in replacement with a new LED module can be expected.

<Modification>
In Embodiment 1, the 2nd LED display part 2 was comprised from 2nd LED2a of multiple sets (In FIG. 1, 4 sets of 2 sets x 2 sets in total). However, the 2nd LED display part 2 does not necessarily need to be comprised from multiple sets, and may be comprised from 1 set 2nd LED2a. However, since the configuration composed of a plurality of sets of second LEDs 2a can use the average value of the luminance of each color as compared with the configuration composed of a set of second LEDs 2a, adverse effects due to variations in individual luminance can be suppressed. .

  In the first embodiment, the luminance correction unit 18 reads the luminance corresponding to the lighting time of the second LED 2a that is the same as or close to the lighting time (actual measurement time) of the first LED 1a stored in the lighting time storage unit 7. The luminance reduction rate of the first LED 1a is measured (predicted).

  Instead of such a configuration, the brightness correction unit 18 performs a regression analysis on the brightness reduction rate and the second cumulative lighting time of the plurality of sets of second LEDs 2a stored in the brightness reduction rate storage unit 11, thereby reducing the brightness. Rate functions kr (t), kg (t), and kb (t) may be calculated. Then, the luminance correction unit 18 applies kr (trmax) by applying the maximum cumulative lighting time trmax, tgmax, tbmax for the first LED 1a to t of the function kr (t), kg (t), kb (t) of the luminance reduction rate, respectively. ), Kg (tgmax), and kb (tbmax) may be measured (predicted) as the luminance reduction rate of the first LED 1a.

  According to such a configuration, even if the length of the second cumulative lighting time of the second LED 2a is not controlled to be equal to or longer than the length of the first cumulative lighting time of the first LED 1a, the luminance reduction rate of the first LED 1a is reduced. Can be predicted.

  Note that the above modification can also be applied to the second embodiment described later.

<Embodiment 2>
The block configuration of the LED display device according to Embodiment 2 of the present invention is the same as the block configuration of the LED display device according to Embodiment 1 (FIG. 1). Hereinafter, in the LED display device according to the second embodiment, the same or similar components as those in the first embodiment are denoted by the same reference numerals, and different components will be mainly described.

  The LED display device 100 according to Embodiment 1 assumes the highest luminance reduction rate among the luminance reduction rates of the first LEDs 1a of the first LED display unit 1, assuming that, for example, the maximum luminance is used as the initial luminance of the first LED 1a. Luminance correction was performed to unify.

  On the other hand, the LED display device 100 according to the second embodiment uses a luminance smaller than the maximum luminance of the first LED 1a (for example, luminance of 50% of the maximum luminance) as the initial luminance of the first LED 1a. According to such a configuration, the luminance correction unit 18 can perform luminance correction so as to unify the smallest luminance reduction rate among the luminance reduction rates of the first LEDs 1 a of the first LED display unit 1. For this reason, the brightness correction unit 18 can adjust (maintain) the brightness of the first LED 1a to a constant initial brightness by correction.

  Specifically, the current theoretical luminance of the first LED 1a of R, G, B is Rp, Gp, Bp, and the theoretical luminance reduction rate of R, G, B in the cumulative lighting time t is kr (t). , Kg (t), kb (t), the corrected luminances Rcomp, Gcomp, Bcomp of the first LEDs 1a of R, G, B are expressed by the following equation (5).

  When the above equation (3) is substituted into the above equation (5), the corrected luminances Rcomp, Gcomp, and Bcomp of the first LEDs 1a of R, G, and B are expressed by the following equation (6). As shown in the following equation (6), the corrected luminances Rcomp, Gcomp, and Bcomp of the R, G, and B first LEDs 1a are corrected to initial luminances R0, G0, and B0 of the R, G, and B first LEDs 1a. Will be.

<Summary of Embodiment 2>
According to the second embodiment, although the initial luminance is lowered, there is an advantage that the luminance can be kept constant before and after correction. The luminance of the first LED 1a can be corrected by changing the duty ratio of the pulse width as in the first embodiment. As described above, by correcting the brightness of the first LED 1a whose brightness has decreased to the initial brightness, it becomes possible to match the brightness of all the first LEDs 1a with the initial brightness. Even if it decreases, the luminance uniformity of the first LED display unit 1 can be maintained.

  In addition, if the above-described control capable of maintaining a constant luminance is applied to a configuration capable of multi-screen display by a plurality of LED panels, the luminance of each LED panel can be similarly maintained constant. Therefore, the luminance of the entire multi-screen display can be kept uniform as described above.

  In the above description, the luminance correction of the first LED 1 a is performed on the output of the video signal processing unit 4. However, as a processing result, the duty ratio of the first drive signal of the first LED 1a, the drive current, or the drive of the first LED display unit 1 may be corrected, and the luminance correction target is the output of the video signal processing unit 4. It is not limited.

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

  DESCRIPTION OF SYMBOLS 1 1st LED display part, 1a 1st LED, 2nd 2nd LED display part, 2a 2nd LED, 7 lighting time memory | storage part, 10 brightness | luminance measuring part, 11 brightness | luminance fall rate memory | storage part, 18 brightness correction part, 100 LED display apparatus.

Claims (7)

A first LED display having a first LED;
A second LED display unit having a second LED having a luminance transition equivalent to that of the first LED;
A lighting time storage unit for storing a first cumulative lighting time of the first LED;
A luminance measuring unit for measuring the luminance of the second LED;
A luminance transition storage unit that stores the luminance transition of the second LED measured by the luminance measurement unit and the second cumulative lighting time of the second LED in association with each other;
Based on the first cumulative lighting time stored in the lighting time storage unit, the luminance transition of the second LED and the second cumulative lighting time stored in the luminance transition storage unit, the first LED of the first LED. An LED display device comprising: a luminance correction unit that corrects luminance. The LED display device according to claim 1,
The first LED includes any one of red, green, and blue LEDs,
The second LED is an LED display device including one of red, green, and blue LEDs. The LED display device according to claim 1 or 2,
The plurality of first cumulative lighting times of the plurality of first LEDs are different,
The brightness correction unit
The longest first cumulative lighting time among the plurality of first cumulative lighting times stored in the lighting time storage unit, the transition of the luminance of the second LED stored in the luminance transition storage unit, and the second cumulative. An LED display device that performs the correction based on a lighting time. The LED display device according to any one of claims 1 to 3,
The brightness correction unit
An LED display device that adjusts the luminance of the first LED to an initial luminance by the correction. The LED display device according to any one of claims 1 to 4,
An LED display device that controls the length of the second cumulative lighting time to be equal to or longer than the length of the first cumulative lighting time. The LED display device according to any one of claims 1 to 5,
The LED display device in which the display of the first LED display unit and the display of the second LED display unit are performed in parallel. The LED display device according to any one of claims 1 to 6,
The first LED display unit is driven based on a drive signal,
The brightness correction unit
A correction coefficient is calculated based on the first cumulative lighting time stored in the lighting time storage unit, the luminance transition of the second LED and the second cumulative lighting time stored in the luminance transition storage unit. An LED display device that corrects the luminance of the first LED by correcting the drive signal using the correction coefficient.

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