High accuracy optical metrology for MicroLED displays and wafers

High-accuracy, traceable color calibration of imaging light measurement devices (ILMDs) is essential for quality control in modern display manufacturing—particularly for LED-based and, increasingly, for inorganic microLED (µLED) technologies. The narrow spectral bandwidth and relatively large manufacturing tolerances of µLEDs present unique metrological challenges that traditional calibration methods struggle to address.
In prior work [1], we introduced advanced calibration strategies designed to accommodate the spectral characteristics of LED-based displays. In this study, we focus on the application of these methods to µLEDs, leveraging real-time calibration directly on the device under test (DUT). This "principle of similarity" ensures traceable, high-accuracy results across a wide range of devices and test patterns.
We present measurement results from ILMD-based evaluations of µLED displays and wafers, comparing them to spectroradiometric reference data. The findings highlight the effectiveness of DUT-specific, live calibration approaches in overcoming the spectral variability inherent to µLED technologies.
[1] Schanz, R., Fischer, F. and Steinel, T. (2024), 58-3: Impact of Calibration Sources on Accuracy of Chromaticity Measurements of LED based Displays. SID Symposium Digest of Technical Papers, 55: 801-804. https://doi.org/10.1002/sdtp.17649