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Production-accompanying measuring technique for LED and LED assembly groups
LEDs are becoming increasingly important in different fields of architectural illumination, for lighting fixtures and for the automotive industry. Because they are small and easy to combine, LED assembly groups are used very often.
To get photometric data of the LEDs, a well adaptable measuring system is necessary. It must be able to capture high dynamic images for different areas of color spaces as well as for different light intensities/luminances.
Moreover, it must be possible to determine intensity gradients and also the uniformity of light sources for both assemblies and Single-LED symbols.
All this information can be determined by means of an imaging photometer or imaging colorimeter within fractions of a second. In addition, there are image-processing operations specially adapted to these problems.
Measuring principle
Depending on the specific application, LEDs can be measured either directly or indirectly. The measuring principle for the indirect measurement is shown in the following figure.
Here, a diffusing screen is mounted at a suitable distance to the LED assembly. The luminance and chromaticity coordinates can then be measured on this screen.
There are applications just as emergency lights, where especially the single results of each LED compared with one another are of interest. So, it has to be checked whether all LEDs have a minimum of intensity (luminance) and also that the color distance between the LEDs is within a predefined tolerance.
IPED software client
The LED Checker package contains also several interfaces for the communication with a process control system.
Results represented in the software user interface or the data can be optionally transferred to external protocol files and programs.
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