JP6739151B2 - LED display device - Google Patents

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 have been used for many applications such as outdoor and indoor advertisement displays due to technological development and cost reduction of LEDs. Specifically, conventionally, the LED display device has been mainly used for displaying a natural image and a moving image of animation. However, in recent years, as the pixel pitch has become narrower, it has become possible to maintain image quality even when the viewing distance is short, and therefore, it is also used as an indoor application such as a conference room or a monitoring application.

Of these, personal computer images that are close to still images are often displayed for monitoring purposes. However, since the brightness of the LED decreases as the lighting time increases, the lighting time of each LED, and thus the brightness reduction rate of each LED, varies depending on the content of the image. As a result, variations in luminance and colors of pixels occur with the lighting time.

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

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

According to the technology of measuring the brightness reduction rate of the LED based on the integrated time by a life test and correcting the brightness using the brightness reduction rate, the brightness variation and the color variation due to the difference in the lighting time of the LED are corrected. It is possible to do so. However, there are inevitably variations in characteristics that are difficult to predict, such as variations in characteristics due to differences in LED manufacturing lots. Therefore, it is difficult to accurately correct the luminance variation based on the integrated time.

Further, with the technique of detecting the brightness from the LED display unit that displays a desired image, the brightness can be corrected with high accuracy, but it is necessary to display the brightness detection image at the time of detecting the brightness. Therefore, in a display system that requires 24-hour operation (for example, the above-described display system for monitoring purposes), the display (operation) is stopped to correct the brightness variation or the like, or the brightness variation is maintained to maintain the display. I had to accept either of the abandoned corrections.

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

An 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 plurality of sets of second LEDs having the same luminance transition as the first LED, and a first accumulation of the first LEDs. A lighting time storage unit that stores a lighting time, a brightness measurement unit that measures the brightness of the plurality of sets of second LEDs, a transition of the brightness of the plurality of sets of second LEDs measured by the brightness measurement unit, and a plurality of the brightness measurement units. a luminance transition storage unit that stores any time in association with the second accumulated lighting time of the set of first 2LED, and the lighting time storage unit the first cumulative lighting time stored in, is from time to time stored in the luminance transition storage unit And a brightness correction unit that corrects the brightness of the first LED based on the transition of the brightness of the plurality of sets of the second LEDs and the second cumulative lighting time. The first LED includes red, green and blue LEDs, each of the plurality of sets of second LEDs includes red, green and blue LEDs, and each of the first LED and the plurality of sets of second LEDs is PWM. Driven by a signal, the lighting time storage unit stores the first cumulative lighting time and the second cumulative lighting time based on the duty ratio of the first LED and the plurality of sets of second LEDs, and the brightness correction unit. Control the length of the second cumulative lighting time used in, to the length of the longest first cumulative lighting time of the plurality of the first cumulative lighting time, the brightness correction unit, the lighting time storage unit The longest first cumulative lighting time among the plurality of stored first cumulative lighting times, the transition of the brightness of the plurality of sets of the second LEDs stored at any time in the brightness transition storage unit, and the second cumulative lighting time. Based on the regression analysis of 1., the brightness of all the LEDs of the first LED display unit is corrected to be the same as the brightness of the first LED with the lowest brightness, and the brightness variations and color variations of all the LEDs are corrected. Suppress.

According to the present invention, the first LED display unit is based on the first cumulative lighting time stored in the lighting time storage unit, the brightness transition of the second LED and the second cumulative lighting time stored in the brightness transition storage unit. The brightness of the first LED of is corrected. As a result, it is possible to suppress luminance variations and color variations of the first LED display unit while the desired image is displayed on the first LED display unit.

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

<Embodiment 1>
FIG. 1 is a block diagram showing the configuration of the LED display device according to the first embodiment 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 correcting unit 5, and a first driving unit 6. The lighting time storage unit 7, the signal generation unit 8, the second drive unit 9, the brightness measurement unit 10, the brightness reduction rate storage unit 11 that is a brightness transition storage unit, and the correction coefficient calculation unit 12 are provided. The brightness correction unit 18 includes the signal correction unit 5 and the 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 brightness measurement unit 10. .. For example, the memory 91 of FIG. 2 is applied to the lighting time storage unit 7 and the brightness reduction 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 of FIG. 2 is realized by executing the program stored in the memory 91.

The memory 91 includes, for example, RAM, ROM, flash memory, EPROM, EEPROM, and other non-volatile or volatile semiconductor memory, magnetic disk, flexible disk, optical disk, compact disk, mini disk, DVD, and the like. 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 the procedure or method of the video signal processing unit 4 or the like, and is realized by, for example, software, firmware, or a combination of software and firmware.

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

Next, an outline of each component of the LED display device 100 of FIG. 1 will be described, and then some components will be described in detail.

<Overview>
The 1st LED display part 1 is used in order to display a desired image, such as a character and a figure, for example. The first LED display unit 1 has a plurality of first LEDs 1a, and is driven based on a first drive signal (in other words, display pattern, drive pattern, drive data) from the first drive unit 6, Lighting control of the individual first LEDs 1a and the like are 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 include R, G, and B LEDs. I'm out. In addition, in the example of FIG. 1A, a total of 16 sets of the first LEDs 1a of 4 sets in the vertical direction×4 sets in the horizontal direction are arranged in a matrix. Then, one set of the first LEDs 1a includes a total of three LEDs of R, G and B, as shown in FIG. 1(b). However, the number of the first LEDs 1a is not limited to this.

The second LED display unit 2 performs a display for measuring (predicting) the transition of the brightness of the first LED display unit 1. Note that the transition of the luminance is, for example, the luminance maintenance rate indicating the current luminance with the initial luminance being 100%, or the luminance reduction rate (=100%−luminance maintenance rate) which is the inverse relationship to the luminance maintenance rate. Including 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 has a plurality of second LEDs 2a, and is driven based on the second drive signal (in other words, display pattern, drive pattern, drive data) from the second drive unit 9, Lighting control of the individual second LEDs 2a and the like are performed.

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

The second LED 2a includes any one of R, G, and B LEDs similarly to the first LED 1a, and the plurality of second LEDs 2a included in the second LED display unit 2 include R, G, and B LEDs. Note that in the example of FIG. 1A, a total of four sets of the second LEDs 2a of two sets in the vertical direction and two sets in the horizontal direction are arranged in a matrix. Then, the set of second LEDs 2a includes a total of three LEDs of R, G, and B, similarly to the set of first LEDs 1a. However, the number of the second LEDs 2a is not limited to this.

In addition, in the first embodiment, the display (drive) of the first LED display unit 1 and the display (drive) of the second LED display unit 2 are performed in parallel. As a result, the first LED 1a and the second LED 2a are turned on in the same environment, and thus it is possible to bring the luminance reduction rates of the two closer to each other.

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

The signal correction unit 5 corrects the brightness of the output signal of the video signal processing unit 4 using the correction coefficient from the correction coefficient calculation unit 12 described later. With this correction, the signal correction section 5 can substantially correct the first drive signal from the first drive section 6 to the first LED display section 1, and thus the brightness 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 times when the first LED 1a is lit).

The signal generation unit 8 generates a signal for generating the second drive signal of 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 brightness measuring unit 10 measures the brightness of the second LED 2a of the second LED display unit 2.

The brightness reduction rate storage unit 11 that is a brightness transition storage unit cumulatively calculates the decrease rate of the brightness of the second LED 2a measured by the brightness measurement unit 10 and the second cumulative lighting time of the second LED 2a (the time when the second LED 2a is turned on). And the time obtained by adding to () are stored in association with each other. The measurement of the brightness measuring unit 10 and the storage of the brightness reduction rate storage unit 11 are performed at any time while the second LED display unit 2 is displayed.

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

Here, the brightness correction unit 18 in FIG. 1 includes the signal correction unit 5 and the correction coefficient calculation unit 12 described above. Therefore, the brightness correction unit 18 is based on the first cumulative lighting time stored in the lighting time storage unit 7 and the brightness reduction rate and the second cumulative lighting time of the second LED 2a stored in the brightness reduction rate storage unit 11. Then, the correction coefficient described above is calculated. Then, the brightness correction unit 18 corrects the brightness of the output signal of the video signal processing unit 4 using the correction coefficient, so that the first drive signal (drive signal) of the first drive unit 6, and thus 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 brightness correction unit 18 determines the longest first cumulative lighting time of the plurality of first cumulative lighting times stored in the lighting time storage unit 7 and the brightness reduction of the second LED 2a stored in the brightness 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 based on the duty ratio included in the output signal at a constant unit time. To do. For example, when the unit time is one hour and the duty ratio is 10% for lighting, the lighting time of 0.1 hour (flashing time excluding the extinguishing time) is calculated every hour. , And is added to the first cumulative lighting time of the lighting time storage unit 7.

FIG. 3 is a diagram showing an example of the relationship between the luminance reduction rate of the green (G) first LED 1a and the lighting time (first cumulative lighting time). A logarithmic scale is applied to the lighting time scale in FIG.

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

In the related art, the brightness reduction rate of the first LED 1a is obtained by measuring the brightness in advance. On the other hand, in the first embodiment, the brightness of the first LED 1a is not actually measured, but the first lighting time is actually measured and associated with the second lighting time substantially the same as the first lighting time. The luminance reduction rate of the second LED 2a is configured to be 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.

The signal generation unit 8 generates a signal that is a second drive signal for controlling the display of the second LED display unit 2 based on the output signal corrected by the signal correction unit 5. 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 determines the maximum value. A signal for driving the second LED display unit 2 is generated with the duty ratio. Accordingly, 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. It 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. Note that this control may be performed for each of R, G, and B.

The brightness measuring unit 10 is arranged to face the second LED display unit 2 and measures the brightness of the second LED 2a. In the first embodiment, the brightness measuring unit 10 measures the brightness of each color of the individual second LEDs 2a.

FIG. 4 is a diagram showing an example of the relationship between the luminance reduction rate of the R, G and B second LEDs 2a and the lighting time (second cumulative lighting time) which is the elapsed time. A logarithmic scale is applied to the lighting time scale in FIG.

As shown in FIG. 4, the brightness of the second LED 2a also decreases with the lighting time similarly to the brightness of the first LED 1a. Here, the luminance reduction rates of the R, G, and B second LEDs 2a can be respectively shown by the functions kr(t), kg(t), and kb(t) of the lighting time t. The functions kr(t), kg(t), and kb(t) are subjected to regression analysis and the like on the luminance reduction rates and the second cumulative lighting times of the plurality of sets of the 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.

The measurement result of the brightness measuring unit 10 and the lighting time of the second LED 2a are stored in the brightness reduction rate storage unit 11 in association with each other. Then, the brightness correction unit 18 reads the brightness (brightness reduction rate) corresponding to the lighting time of the second LED 2a stored in the lighting time storage unit 7 that is the same as or close to the lighting time of the first LED 1a (actual measurement time). As a result, in the first embodiment, the luminance reduction rate of the first LED 1a can be substantially measured without actually measuring the luminance of the first LED 1a.

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

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

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

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

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 brightness correction unit 18 obtains the maximum brightness reduction rate krgb(tmax) represented by the following expression (1).

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

Here, the current theoretical brightness of the R, G, B first LEDs 1a is Rp, Gp, Bp, and the theoretical brightness reduction rate of the R, G, B first LEDs 1a at 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, and Bcomp of the R, G, and B first LEDs 1a are expressed by the following equation (2). Indicated by. Note that 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) at 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 the expression of the correction coefficient to be obtained in step S4.

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

Substituting the above equation (3) into the above equation (2), the corrected brightness Rcomp, Gcomp, Bcomp of the R, G, B first LEDs 1a is given by the following equation (4). As shown in the following expression (4), the brightnesses Rcomp, Gcomp, and Bcomp are unified to correct the initial brightnesses R0, G0, and B0 of the R, G, and B first LEDs 1a by the maximum brightness reduction rate krgb(tmax). It will be what you did.

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

Here, for example, a PWM method is applied to the brightness adjustment of the first LED 1a. FIG. 6 is a diagram showing an example of PWM drive used in the PWM method. FIG. 6A shows a PWM basic cycle (pulse cycle), and a period of one frame period or less of the video signal is applied to the PWM basic cycle. FIG. 6B shows the case where the duty ratio of the pulse width is, for example, 85%, and FIG. 6C shows the case where the duty ratio of the pulse width is, for example, 80%. Since the pulse cycle is very short, blinking of the LED of the pulse cycle is perceived as lighting by human eyes. In such a PWM method, the smaller the duty ratio is, the smaller the proportion of the lighting time of the LED is, and thus the luminance perceived by human eyes is lower in the case of FIG. 6C than in the case of FIG. 6B. Become. As described above, by changing the duty ratio of the pulse width, it becomes possible to adjust the brightness of the first LED 1a.

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

<Summary of First Embodiment>
According to the LED display device 100 of the first embodiment that performs the above-described correction, the corrected brightness of the first LED display unit 1 is lower than the uncorrected brightness as a whole, but The brightness of the first LED 1a can be unified to the brightness of the LED having the longest lighting time (the brightness with the largest brightness reduction rate). Therefore, it is possible to maintain the brightness uniformity and the white balance of the entire first LED display unit 1, and it is possible to suppress the brightness variation and the color variation.

In addition, in the first embodiment, the second LED display unit 2 is driven at the maximum duty ratio of the first LED display unit 1. As a result, the length of the second cumulative lighting time of the second LED 2a becomes equal to or longer than the length of the first cumulative lighting time of the first LED 1a, so that the decrease in brightness of the second LED 2a is equal to or less than the decrease in brightness of the first LED 1a. Get faster This means that the brightness reduction rate storage unit 11 stores the brightness reduction rate of the second LED 2a having the longest lighting time as a future brightness reduction rate of the first LED 1a. In the first embodiment, the brightness reduction rate of the first LED 1a is predicted based on the brightness reduction rate of the second LED 2a stored in the brightness reduction rate storage unit 11. Therefore, the prediction accuracy of the brightness reduction rate of the first LED 1a, and eventually The accuracy of brightness correction can be improved.

In the conventional technology, the luminance reduction rate of the first LED display unit 1 cannot be measured while the desired image is continuously displayed on the first LED display unit 1, and the luminance variation and the color variation can be suppressed. There wasn't. On the other hand, in the first embodiment, the luminance reduction rate of the second LED display unit 2 different from the first LED display unit 1 is actually measured while the desired image is displayed 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 variation and color variation. As a result, it is possible to expect a reduction in replacement with a new LED module.

<Modification>
In the first embodiment, the second LED display unit 2 is composed of a plurality of sets (two sets in the vertical direction×two sets in the horizontal direction, a total of four sets) of the second LEDs 2a. However, the second LED display unit 2 does not necessarily have to be composed of a plurality of sets, and may be composed of one set of the second LEDs 2a. However, since the configuration including a plurality of sets of the second LEDs 2a can use the average value of the luminance of each color as compared with the configuration including one set of the second LEDs 2a, it is possible to suppress the adverse effect due to the variation in the individual luminance. ..

In the first embodiment, the brightness correction unit 18 reads the brightness corresponding to the lighting time of the second LED 2a stored in the lighting time storage unit 7 that is the same as or close to the lighting time (measured time) of the first LED 1a. , 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 or the like on the brightness decrease rates and the second accumulated lighting times of the plurality of sets of the second LEDs 2a stored in the brightness decrease rate storage unit 11 to reduce the brightness. The rate functions kr(t), kg(t), kb(t) may be calculated. Then, the brightness correction unit 18 applies the maximum cumulative lighting times trmax, tgmax, tbmax of the first LED 1a to t of the functions of brightness reduction rate kr(t), kg(t), kb(t), respectively. ), kg(tgmax), 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 brightness reduction rate of the first LED 1a can be reduced. Can be predicted.

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

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

In the LED display device 100 according to the first embodiment, assuming the case where the maximum brightness is used as the initial brightness of the first LED 1a, for example, the maximum brightness decrease rate among the brightness decrease rates of the first LEDs 1a of the first LED display unit 1 is set. Brightness correction was performed so as to be unified.

On the other hand, the LED display device 100 according to the second embodiment uses a brightness smaller than the maximum brightness of the first LED 1a (for example, brightness of 50% of the maximum brightness) as the initial brightness of the first LED 1a. With such a configuration, the brightness correction unit 18 can perform the brightness correction so that the brightness reduction rate of each first LED 1a of the first LED display unit 1 is unified to the smallest brightness reduction rate. Therefore, the brightness correction unit 18 can adjust (maintain) the brightness of the first LED 1a to a constant initial brightness by the correction.

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

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

<Summary of Second Embodiment>
According to the second embodiment, although the initial luminance is low, there is an advantage that the luminance can be kept constant before and after the correction. The brightness 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 is possible to match the brightness of all the first LEDs 1a to the initial brightness, and the brightness of the first LED 1a changes with time. Even if it decreases, it becomes possible to maintain the brightness uniformity of the first LED display unit 1.

If the above-described control capable of maintaining the brightness constant is applied to a configuration capable of performing multi-screen display by a plurality of LED panels, the brightness of each LED panel can be maintained constant similarly. Therefore, similar to the above, the brightness of the entire multi-screen display can be kept uniform.

In the above description, the brightness correction of the first LED 1a is performed on the output of the video signal processing unit 4. However, as the 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 target of the brightness correction is the output of the video signal processing unit 4. It is not limited.

It should be noted that, within the scope of the invention, the present invention can freely combine each embodiment and each modification, and appropriately change or omit each embodiment and each modification.

1 1st LED display part, 1a 1st LED, 2 2nd LED display part, 2a 2nd LED, 7 lighting time storage part, 10 brightness|luminance measurement part, 11 brightness|luminance fall rate storage part, 18 brightness|luminance correction|amendment part, 100 LED display device.

Claims (5)

A first LED display section having a first LED;
A second LED display section having a plurality of sets of second LEDs having the same transition of brightness as the first LED;
A lighting time storage unit that stores a first cumulative lighting time of the first LED;
A brightness measurement unit that measures the brightness of the plurality of sets of second LEDs;
A luminance transition storage unit that stores the transition of the luminance of the plurality of sets of the second LEDs measured by the luminance measurement unit and the second accumulated lighting time of the plurality of sets of the second LEDs in association with each other at any time ,
Based on the first cumulative lighting time stored in the lighting time storage unit, the brightness transitions of the plurality of sets of the second LEDs and the second cumulative lighting time stored in the brightness transition storage unit at any time , A brightness correction unit that corrects the brightness of the first LED,
The first LED includes red, green and blue LEDs,
Each of the plurality of sets of second LEDs includes red, green and blue LEDs,
Each of the first LED and the plurality of second LEDs is driven by a PWM signal,
The lighting time storage unit,
Storing the first cumulative lighting time and the second cumulative lighting time based on the duty ratios of the first LED and the plurality of sets of second LEDs;
The length of the second cumulative lighting time used in the brightness correction unit is controlled to be the longest length of the first cumulative lighting time of the plurality of the first cumulative lighting times,
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, and the transition of the brightness of the plurality of sets of second LEDs stored in the brightness transition storage unit at any time, and Based on the regression analysis of the second cumulative lighting time, the luminance of all the LEDs of the first LED display unit is corrected to be the luminance of the first LED with the lowest luminance, and the luminance of all the LEDs is corrected. LED display device which suppresses the variation in color and the variation in color. The LED display device according to claim 1, wherein
The LED display device in which the brightness of the first LED having the lowest brightness is the brightness of the first LED having the longest first cumulative lighting time. The LED display device according to claim 1 or 2, wherein
The brightness correction unit,
The LED display device adjusts the brightness of the first LED to an initial brightness by the correction. The LED display device according to any one of claims 1 to 3,
An 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 4,
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 brightness transition of the second LED stored in the brightness transition storage unit, and the second cumulative lighting time. An LED display device that corrects the brightness of the first LED by correcting the drive signal using the correction coefficient.

Images