Measuring setup for recording aging processes of individual light-emitting diodes

Abstract

Measuring arrangement for recording aging processes of individual light-emitting diodes (LEDs), comprising: - a plurality of light-emitting diodes (LEDs), comprising a red light-emitting diode (R), a green light-emitting diode (G) and a blue light-emitting diode (B); - a control unit (CTRL) set up for individual brightness intensity control of each of the light-emitting diodes (LEDs), wherein - at least one photodiode (FD), configured for measuring the brightness intensity of at least one light-emitting diode (LED), which is not the red light-emitting diode (R), is provided, whereby the red light-emitting diode (R) cannot be monitored, wherein the control unit (CTRL) is configured to detect a relative change in brightness intensity of each of the light-emitting diodes (LEDs) depending on a first measurement and a second time-delayed measurement, wherein the majority of light-emitting diodes (LEDs) and the photodiode (FD) are formed in such a way that they cannot be separated without destruction and all components are arranged in a common housing which has transparent or semi-transparent window areas.

Description

[0001] The present invention relates to a measuring arrangement for detecting the aging processes of individual light-emitting diodes (LEDs), which makes it possible to detect and subsequently compensate for a loss of brightness in LEDs. This involves a relative measurement of brightness intensity. The present invention further relates to a correspondingly configured method for detecting the aging processes of individual LEDs and to a computer program product with control commands that implement the method.

[0002] US 2008 / 0251690A1 describes an LED light source in which each LED is monitored by a photodiode. By temporarily switching off individual LEDs, the light intensity can be measured and the power regulated to ensure stable brightness and color temperature.

[0003] US 2014 / 0035465A1 discloses a system for tunable-white LED luminaires that processes color coordinates and controls the light output of multiple sources. Aging and brightness loss of the LEDs are compensated for by adjusting the intensity, ensuring stable color and brightness throughout their lifespan.

[0004] US 2010 / 0327764A1 discloses an intelligent lighting device in which LEDs are briefly switched off to receive optical control commands or to measure light. This allows for the cost-effective integration of functions such as remote control, dimming, or color adjustment.

[0005] US 2016 / 0003670A1 discloses a method for stabilizing luminous flux and color over the lifetime of the LED. A reference laser is used to calibrate a photodetector, thereby monitoring the LED output and adjusting the control to ensure consistent characteristics.

[0006] According to established methods, the absolute brightness values ​​of LEDs are measured and recorded during their manufacturing process. From a number of such test series, it is expected that conclusions can be drawn about the anticipated aging processes of an LED, based on the absolute values ​​of changes in its brightness. Thus, the corresponding parameters are stored, for example, in a table and often delivered to the end customer in an unaltered form.

[0007] It is already known to verify a single or multiple LEDs by using a color sensor that measures their light-emitting behavior. Sensors based on CCD or CMOS technology are commonly used for this purpose. These conventionally used components are relatively large and therefore preclude a compact design. Furthermore, they require complex measurements in specific wavelength ranges to analyze the colored light-emitting behavior of the LEDs under test. Current technology therefore relies on relatively sophisticated color sensors, as precise absolute values ​​often need to be measured, and specific color spectra, such as the red-green-blue RGB scheme, must be analyzed. In practice, this represents a considerable technical challenge.

[0008] Generally, various designs and configurations of light-emitting diodes (LEDs) are known, but all are subject to an aging process. This can occur, for example, because heat is generated during operation, which in turn leads to or accelerates this aging process within the LED. This aging process manifests itself in the overall loss of brightness of the LED. Therefore, if an LED is initially driven with a certain current and then driven again with the same current over a longer period of aging, the first test will result in a brighter luminous value than the second test.

[0009] This is particularly disadvantageous in the present case, as the invention relates specifically to the automotive sector, where significant safety requirements apply. These safety requirements are specified, among other things, in various DIN standards and must be complied with by the manufacturer.

[0010] Thus, compared to the state of the art, it is particularly disadvantageous that the LEDs undergo an aging process that can only be compensated for with considerable technical effort. It is especially disadvantageous that color sensors are used which are particularly unsuitable in their design and also entail significant additional technical complexity. The manufacture of a color sensor itself is technically demanding. Therefore, according to known methods, a person skilled in the art has the choice of either simply accepting the aging process of LEDs or compensating for it in a technically complex manner.

[0011] It is therefore desirable to provide a method and a corresponding system configuration that enables the end customer to receive a single or multiple LEDs that consistently exhibit the same lighting behavior over many years. Manufacturers are required to ensure that changes in lighting behavior can be detected in a technically simple and, in particular, highly reliable manner.

[0012] It is therefore an object of the present invention to propose a measuring arrangement for detecting the aging processes of individual light-emitting diodes. Furthermore, it is an object of the present invention to propose a corresponding method for detecting the aging processes of individual light-emitting diodes, as well as a computer program product with control commands that implement the proposed method.

[0013] The problem is solved by a measuring arrangement for recording aging processes with the features of claim 1. Further advantageous embodiments are specified in the dependent claims.

[0014] Accordingly, a measuring arrangement for detecting aging processes of individual light-emitting diodes is proposed, comprising a plurality of light-emitting diodes, a control unit configured for individual brightness intensity control of each of the light-emitting diodes, wherein at least one photodiode configured for brightness measurement of at least one light-emitting diode is provided, wherein the control unit is configured to detect a relative change in brightness intensity of each light-emitting diode depending on a first measurement and a second time-delayed measurement, wherein the plurality of light-emitting diodes LED and the photodiode FD are formed in such a way that they cannot be separated without destruction and all components are arranged in a common housing which has transparent or semi-transparent window areas.

[0015] The present invention offers the advantage that aging processes, which manifest as changes in brightness intensity, can be both detected and compensated for. For this purpose, individual light-emitting diodes (LEDs) are provided, typically RGB LEDs. However, the present invention is not limited to this but rather relates to any number of LEDs to be monitored. Thus, the number of LEDs included in the plurality of LEDs can preferably be three or four. Furthermore, it is also possible to connect several LEDs in series, thereby monitoring the entire series. Therefore, an aspect of the present invention is that a plurality of LEDs comprises three or four LEDs, and that multiples of this number can be achieved by connecting them in series.

[0016] Furthermore, a control unit is provided that addresses the individual LEDs within the group of LEDs. Typically, this is achieved by applying a specific current or voltage to each individual LED, thereby implicitly setting a certain brightness level. As described earlier, a particular disadvantage of LEDs is that an applied voltage does not always produce the same brightness. Therefore, the control unit is generally able to address the individual LEDs in such a way that they also increase their brightness. Thus, if an LED ages, the applied voltage must be increased over time to maintain a consistent brightness level.

[0017] The control unit is thus configured to individually regulate the brightness intensity of each LED. Individual brightness intensity control means that each LED can be addressed independently. This allows the brightness of each LED to be adjusted separately. Furthermore, the control unit can be used to set a mixing ratio of the individual LEDs to achieve a specific color value. For example, the intensity of a red LED, a green LED, and a blue LED can be adjusted to produce a specific color value. However, if individual LEDs lose brightness, this mixing ratio will be disrupted.

[0018] According to the invention, it is particularly advantageous that a photodiode is used. Compared to the prior art, this offers the particular advantage that a photodiode can be provided in a particularly simple technical manner and that the readout process is technically less complex. While color sensors are used in the prior art, it has been found, particularly surprisingly, that a certain otherwise disadvantageous error tolerance of the photodiode is negligible according to the invention. This is because the absolute values ​​measured according to conventional methods are not important; rather, two measurements are taken at different times, and the photodiode is used only to determine the relative difference between the two measurements. Thus, it is particularly advantageous according to the invention that particularly simple photodiodes can be used here.Experts are generally discouraged from using photodiodes because they often measure less accurately than color sensors and do not necessarily measure a color spectrum. Therefore, a relatively inexpensive sensor can be used whose measurement tolerance does not negatively affect the result of the brightness intensity measurement. Consequently, a measuring device in the form of a photodiode can be used, which is both reliable and requires minimal technical effort.

[0019] The photodiode, or at least one photodiode, is positioned relative to the LED being measured for measuring its brightness intensity in such a way that a direct line of sight is possible. Alternatively, there can be no direct line of sight between the photodiode and the LED, but rather the photodiode can be oriented so that it measures only reflected passive light. Those skilled in the art are aware of other arrangements that allow a photodiode to measure a light source. It is particularly advantageous for the photodiode to be located in close proximity to the LED. Here, too, a tolerance is advantageously provided, since the present method or the proposed measuring arrangement relies solely on relative values.Therefore, the spatial distance between the photodiode and the light-emitting diode does not need to be specifically defined; rather, it is advantageous if the photodiode is always arranged in the same position or distance to the light-emitting diode during the measurements.

[0020] Furthermore, it is possible to measure the brightness intensity of a single LED using a photodiode, or to measure multiple LEDs using a single photodiode. The photodiode can be positioned relative to one or more LEDs in such a way that the corresponding luminous behavior or brightness intensity can be measured. In particular, it is possible to design a photodiode to measure across a broadband or multiband spectrum. Thus, it is especially advantageous that a single photodiode can measure any subset of red, green, and blue light. This can be achieved by designing the photodiode to measure the individual spectra of different LEDs. Therefore, a single photodiode is sufficient to measure any number of LEDs, preferably three or four, each emitting a characteristic wavelength.Furthermore, it is also possible to provide a separate, dedicated photodiode for each individual LED. In this case, the photodiode can be positioned in close proximity to the LED that it is intended to measure.

[0021] Furthermore, it is also possible to arrange photodiodes redundantly in such a way that multiple photodiodes are provided for each light-emitting diode. This prevents the failure of a single photodiode. Additionally, it is possible to average the measured values ​​of individual photodiodes to obtain a particularly reliable average value.

[0022] Due to the aging process, an initial measurement and a subsequent, time-delayed measurement of the brightness intensity of at least one LED are performed. This can be a recurring measurement interval, or the second measurement can be taken only after a predetermined time, depending on the start time of the first measurement. A measurement time can be statically defined, or a relative measurement interval can be determined, after which the second measurement is taken based on the first. Furthermore, it is possible to adjust the measurement interval, i.e., the time delay, depending on the LED's usage. For example, it is advantageous to measure LEDs that are used particularly frequently or for particularly long periods more often and to determine any changes in brightness intensity compared to at least one previous measurement point.The present invention is by no means limited to a first measurement and a second, time-delayed measurement, but rather allows for a multitude of measurements, wherein the preceding second, time-delayed measurement again becomes the first measurement and thus represents a relative starting point with respect to a further second measurement. Therefore, any number of time-delayed measurements is possible, with respect to which the relative change in brightness intensity can be determined according to the invention. It is possible to set any desired time offset to accommodate the underlying application scenario of the light-emitting diodes.

[0023] Thus, in the first measurement, the brightness intensity of at least one LED is measured, and in the second measurement, taken at a later time, a second brightness intensity of the previously measured LED(s) is measured. From this, the relative change in brightness intensity can be determined. This can, for example, involve subtracting the two brightness intensities. It should be particularly noted that, according to the present invention, the absolute values ​​are not the primary focus; rather, only the relative changes in brightness intensity are used, such that any existing difference is compensated for according to further optional process steps or with further optional structural features.

[0024] This offers a particularly inventive advantage: an inaccuracy in the measurement of absolute brightness intensities can be accepted without leading to a distorted result. Even if a photodiode were faulty, the same error would occur in the second measurement. Therefore, the change in brightness intensity can still be accurately determined and compensated for accordingly. For example, if the relative change in brightness intensity shows that the luminosity has decreased by a certain percentage, the control unit can increase the applied voltage by that percentage to restore the same brightness intensity. A person skilled in the art can recognize the extent to which a linear relationship exists between the applied voltage and the change in brightness intensity.Thus, the expert can also determine to what extent a light-emitting diode needs to be controlled to compensate for a change in brightness intensity. Therefore, a measuring setup along with a corresponding method for detecting and compensating for aging processes, i.e., correcting them, is proposed.

[0025] According to one aspect of the present invention, the control unit is configured to substantially compensate for the detected change in brightness intensity. This has the advantage that the change in brightness intensity can be compensated at least to such an extent that the human user cannot detect any change in the lighting behavior of the LEDs. Thus, directly after the second measurement, the change in brightness intensity can be compensated so that the original luminosity of the individual LEDs is restored. It is particularly preferred that the change in brightness intensity be completely compensated, but this can be technically very complex. Therefore, it is particularly advantageous according to the invention that the change in brightness intensity is substantially compensated. However, even after many years of use of the LEDs, the end user, for example a driver, will not notice any difference in luminosity or brightness.in the mixing ratio of the individual light-emitting diodes.

[0026] According to a further aspect of the present invention, the at least one light-emitting diode (LED) is controlled such that the brightness intensity of the first measurement is established. This has the advantage that the first measurement can be stored as a reference point, and then, after the second measurement at a later time, the original luminance or brightness intensity can be restored. This ensures that the brightness intensity value, as it could be achieved at the time of manufacture, can always be set throughout the entire life cycle of the LED. It should be noted that a brightness intensity measurement can also be performed as a function of an applied voltage or current.To accurately determine changes in brightness intensity due to aging, the LED must be operated with identical parameters for both the first and second measurements. This allows for dimming the LED(s) using pulse-width modulation (PWM). Therefore, if an LED is operated at 100% brightness during the first measurement, it must also be operated at 100% brightness during the second measurement. Conversely, if the LED is dimmed to 50% during the first measurement, it must be dimmed accordingly for the second measurement. The use of PWM for dimming LEDs is already familiar to experts.

[0027] According to a further aspect of the present invention, the majority of the light-emitting diodes and the at least one photodiode are arranged in a housing. This has the advantage that the photodiode can be shielded in such a way that only the brightness intensity of the light-emitting diodes to be measured is detectable. Thus, according to the invention, it is prevented that other light sources could affect the photodiodes and thereby distort the measurement results. This is particularly advantageous because light-emitting diodes always require a housing, and therefore the photodiode(s) can be integrated into this existing housing. Thus, the arrangement of the light-emitting diodes and the photodiodes in the housing can be carried out in a single step.

[0028] According to the present invention, the majority of light-emitting diodes and the at least one photodiode are formed in one piece. This has the advantage that the light-emitting diodes and the photodiodes are arranged relative to each other in such a way that they cannot be separated without damage. This is preferably achieved by arranging the light-emitting diodes and the photodiodes in a common housing, such that the housing, comprising the light-emitting diodes and the photodiodes, forms a single unit. It is not essential that the light-emitting diodes and the photodiode are arranged relative to each other in such a way that they are in contact. Rather, the proposed measuring arrangement is packaged in a housing in such a way that it can be delivered as a single unit.

[0029] According to another aspect of the present invention, the control unit is a microcontroller, a finite state machine, an analog control loop, and / or an electronic component. This has the advantage that the control unit can be manufactured in a variety of designs and, in particular, that existing control units can be reused. Those skilled in the art will recognize that the control unit can also include other components, such as a light-emitting diode driver.

[0030] According to a further aspect of the present invention, the plurality of light-emitting diodes (LEDs) are configured as a red LED, a green LED, and a blue LED. This has the advantage that existing control methods and, in particular, existing LED arrangements can be reused according to the invention. Thus, any desired color value, i.e., wavelength, can be set using the proposed LEDs by means of a mixing ratio. Therefore, existing LEDs can also be retrofitted in an inventive manner by simply providing photodiodes. The proposed measuring arrangement and method are thus also suitable for retrofitting existing LEDs by providing a plurality of LEDs and a control unit. In further process steps, the photodiodes are then...the photodiode was provided and the control unit was adapted in accordance with the characterizing part of the independent patent claim, which is directed to the measuring arrangement.

[0031] According to a further aspect of the present invention, the majority of the light-emitting diodes are configured as a red light-emitting diode, a green light-emitting diode, a blue light-emitting diode, and a white light-emitting diode. This has the advantage that existing light-emitting diodes can be reused and, in particular, that the proposed measuring arrangement or method can be applied to any type of light-emitting diode.

[0032] According to a further aspect of the present invention, the photodiode is designed to be broadband. This has the advantage that several color spectra can be measured using the photodiode in such a way that a brightness intensity measurement can be performed for each of the proposed LEDs of different wavelengths. Thus, the advantage arises that, for example, only a single photodiode is required, which can then measure the color spectra, for example, red, green, and blue, separately. In this case, however, it is not necessary to use a so-called CCD sensor or a CMOS sensor. Instead, a single photodiode is provided which can measure the individual LEDs separately.

[0033] According to a further aspect of the present invention, a photodiode is provided for each of the green and blue LEDs. This has the advantage that those LEDs that are particularly sensitive to temperature are monitored by means of their own photodiode. Surprisingly, it was found that a red LED is subject to a lesser aging process than the other LEDs, since a red LED produces less heat than a green or a blue LED. Therefore, it is particularly advantageous according to the invention that even if three or four LEDs are installed, only two or three photodiodes are required. This way, the red LED can always remain unmonitored, since it generates less heat, thus saving the need for its corresponding photodiode.This results in a particularly robust measuring system that can also be manufactured with minimal technical effort. Furthermore, the proposed measuring arrangement can be operated efficiently, which is especially advantageous when several measuring arrangements are connected in series.

[0034] According to a further aspect of the present invention, a separate photodiode is provided for each light-emitting diode (LED) to measure its brightness intensity. This has the advantage that the corresponding change in brightness intensity can be measured particularly reliably for each LED. For example, if the majority of LEDs have three LEDs, then three photodiodes are provided, and if there are four LEDs, then four photodiodes are provided. This allows for a particularly precise determination of changes in the brightness intensity of individual LEDs.

[0035] According to another aspect of the present invention, the change in brightness intensity is detected as a function of user input. This has the advantage that a user who prefers a specific color spectrum can, for example, set this as the interior lighting of their vehicle. Since this color spectrum, and thus the operation of the corresponding LED, is particularly prevalent, it experiences a more intense and faster aging process compared to the other LEDs. If, for example, a user generally selects red interior lighting for their vehicle, the red LED in particular is subject to increased wear and tear or an accelerated aging process. Therefore, it is possible to perform the first and second measurements particularly frequently for the red LED. This allows the change in brightness intensity to be detected more often and compensated for accordingly.

[0036] However, if the user input specifies that a particular LED should never be addressed, then its brightness intensity changes do not need to be monitored and compensated for. Nevertheless, it is advantageous to monitor and compensate for these changes at least occasionally, as natural aging processes may also be present. Therefore, the measurements, monitoring, and compensation are performed with varying frequency on different LEDs. This, in turn, reduces technical complexity.

[0037] The problem is also solved by a method for detecting aging processes of individual light-emitting diodes, comprising the steps of providing a plurality of light-emitting diodes and providing a control unit configured for individual brightness intensity control of each of the light-emitting diodes, wherein at least one photodiode is provided for measuring the brightness intensity of at least one light-emitting diode, wherein the control unit detects a relative change in brightness intensity of each light-emitting diode depending on a first measurement and a second, time-delayed measurement, wherein the plurality of light-emitting diodes (LEDs) and the photodiode (FD) are formed in such a way that they cannot be separated without destruction and all components are arranged in a common housing which has transparent or semi-transparent window areas.

[0038] According to a further aspect of the present invention, the detected change in brightness intensity is essentially compensated. This has the advantage that the change in brightness intensity is not merely detected, but also compensated. Essentially, this means that the change in brightness intensity is completely or at least so compensated that the human user does not perceive any color deviation.

[0039] The task can also be solved by a computer program with control commands that implement the proposed method or operate the proposed measurement setup. Thus, the method can be provided as software or in hardware.

[0040] It is particularly advantageous that the proposed measurement setup has structural features that can also be implemented as process steps. Furthermore, it is possible to model the proposed process steps as structural features of the measurement setup. The computer program is suitable for implementing the individual process steps, operating the measurement setup, or at least operating individual components. Overall, the functionality provided by the measurement setup can therefore also be implemented as process steps.

[0041] Further advantageous features are explained in more detail with reference to the accompanying figures. They show: Fig. 1: a block diagram of a measuring arrangement for detecting aging processes according to one aspect of the present invention, and Fig. 2: a schematic flowchart of a method for detecting aging processes according to a further aspect of the present invention.

[0042] Fig. Figure 1 shows a top view of the proposed compact LED array, with LEDs arranged on the left. These are a red LED (R), a green LED (G), and a blue LED (B). On the right is an MLED controller, i.e., a control unit (CTRL). Furthermore, a photodiode (FD) is positioned near each LED to measure its brightness intensity. The photodiodes are communicatively coupled to the control unit. Logic is implemented on the control unit that triggers the proposed measurements and receives the corresponding measured values. From the first and second measurements, the control unit can then determine the relative change in brightness intensity.

[0043] As in the present case Fig. As can be seen in Figure 1, all necessary components are installed within the housing. This allows the control unit and the LEDs to be placed in the same housing. The housing is designed to be partially opaque, with transparent or semi-transparent window areas. These window areas allow the set brightness intensity of the individual LEDs to be observed from outside the housing. This can be achieved by addressing the LEDs in a specific mixing ratio, resulting in a predetermined color value. Thus, the LEDs are operated using colored light. A chip package, also known as a package, is particularly suitable as a housing.

[0044] In this case, the window area is typically not completely transparent, so that a certain percentage of the light generated by the LEDs is reflected back into the housing. According to the invention, it is particularly advantageous that the photodiodes determine only the relative change in brightness intensity and thus do not only measure the brightness intensity of the individual LEDs, but also take all system components involved, including the reflective window area. Conventional methods would distort the measurement results, as absolute intensity values ​​are typically used in the prior art. Therefore, the dimensions of the housing are also disregarded, since only a relative value for the change in brightness intensity is used.According to conventional methods, absolute measured values ​​can already be distorted simply because the housing of one group of LEDs differs from that of a second group. Since conventional methods only use static values, they do not react flexibly to specific configurations of other system components, such as the window area and housing dimensions.

[0045] According to the invention, no distortion occurs because the change in brightness intensity is always measured under identical conditions. Thus, this change is reliably compensated for. Therefore, the proposed measuring arrangement and method are particularly suitable for automotive applications, as the LEDs can be safety-relevant and are read out by machines, especially in autonomous driving systems. Therefore, deviations in brightness intensity must be detected and compensated for. Thus, the invention offers the advantage that the proposed measuring method and arrangement operate with exceptional reliability and, in particular, provide and operate LEDs with very high color fidelity.

[0046] Fig.Figure 2 shows in a schematic flowchart a method for detecting aging processes of individual light-emitting diodes, comprising the steps of providing 100 a plurality of light-emitting diodes, providing 101 a control unit configured for individual brightness intensity control of each of the light-emitting diodes, wherein at least one photodiode is provided 102 for measuring the brightness intensity of at least one light-emitting diode, wherein the control unit detects a relative change in brightness intensity of each light-emitting diode 105 as a function of a first measurement 103 and a second time-delayed measurement 104, wherein the plurality of light-emitting diodes LED and the photodiode FD are formed in such a way that they cannot be separated without destruction and all components are arranged in a common housing which has transparent or semi-transparent window areas.In a further, optional process step 106, the change in brightness intensity is compensated completely or at least approximately.

[0047] Not shown here is a computer program product with control commands that implement the proposed method or operate the proposed measurement setup. In general, the method can be provided as software or in hardware.

Claims

[1] Measuring arrangement for detecting aging processes of individual light-emitting diodes (LEDs), comprising: - a plurality of light-emitting diodes (LEDs), comprising a red light-emitting diode (R), a green light-emitting diode (G) and a blue light-emitting diode (B); - a control unit (CTRL) set up for individual brightness intensity control of each of the light-emitting diodes (LEDs), wherein - at least one photodiode (FD), configured for measuring the brightness intensity of at least one light-emitting diode (LED), which is not the red light-emitting diode (R), is provided, whereby the red light-emitting diode (R) cannot be monitored, wherein the control unit (CTRL) is configured to detect a relative change in brightness intensity of each of the light-emitting diodes (LEDs) depending on a first measurement and a second time-delayed measurement, wherein the majority of light-emitting diodes (LEDs) and the photodiode (FD) are formed in such a way that they cannot be separated without destruction and all components are arranged in a common housing which has transparent or semi-transparent window areas. [2] Measuring arrangement according to claim 1, characterized by , that the control unit (CTRL) is set up to substantially compensate for the detected change in brightness intensity. [3] Measuring arrangement according to claim 1 or 2, characterized by, that the at least one light-emitting diode (LED) is controlled in such a way that the brightness intensity of the first measurement is achieved. [4] Measuring arrangement according to one of the preceding claims, characterized by , that the majority of the light-emitting diodes (LEDs) and the at least one photodiode (FD) are arranged in a housing. [5] Measuring arrangement according to one of the preceding claims, characterized by that the control unit (CTRL) is a microcontroller, a finite state machine, an analog control loop and / or an electronic component. [6] Measuring arrangement according to one of the preceding claims, characterized by , that the majority of light-emitting diodes (LEDs) are red light-emitting diodes (R), green light-emitting diodes (G), blue light-emitting diodes (B) and white light-emitting diodes. [7] Measuring arrangement according to one of the preceding claims, characterized by that the photodiode (FD) is designed to be broadband. [8] Measuring arrangement according to any one of claims 1 to 7, characterized by , that for each light-emitting diode (LED), except the red light-emitting diode, a separate photodiode (FD) is provided to measure its brightness intensity. [9] Measuring arrangement according to one of the preceding claims, characterized by , that the change in brightness intensity is recorded depending on user input. [10] Method for detecting aging processes of individual light-emitting diodes (LEDs), comprising the steps: - Providing (100) a plurality of light-emitting diodes (LEDs), comprising a red light-emitting diode (R), a green light-emitting diode (G) and a blue light-emitting diode (B); - Providing (101) a control unit (CTRL) configured to individually control the brightness intensity of each of the light-emitting diodes (LEDs), wherein - at least one photodiode (FD) is provided for measuring the brightness intensity of at least one light-emitting diode (LED) which is not the red light-emitting diode (R), (102) whereby the red light-emitting diode (R) is not monitored, wherein the control unit (CTRL) detects a relative change in brightness intensity of each of the light-emitting diodes (LED) depending on a first measurement (103) and a second time-delayed measurement (104) (105), wherein the majority of light-emitting diodes (LED) and the photodiode (FD) are formed in such a way that they cannot be separated without destruction and all components are arranged in a common housing which has transparent or semi-transparent window areas. [11] Method according to claim 10, characterized by , that the detected change in brightness intensity is essentially compensated (106). [12] Computer program product with control commands implementing the method according to one of claims 10 or 11.

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