Dr. Tobias Steinel
Location: Display Week 2021 Virtual Conference
Displays require a high uniformity of luminance and color for a satisfying user experience. Consequently, most mass produced displays are tested by imaging light measurement devices (ILMD) to assure uniformity. The upcoming μLED display technology promises high contrast, fast response time, wide color gamut, low power consumption, and long lifetime. On the flip side, the technology is challenging for optical quality control, since μLED production tolerances with respect to color can currently be much larger than for LC and OLED display technologies. Especially the narrow spectral bandwidth of μLEDs can introduce large measurement errors due to the unavoidable mismatch between the measurement device’s physical color filters and the CIE1931 tristimulus functions.
Additionally, millions of individual μLEDs have to be tested quickly for just a single high-resolution display (e.g. 25 million μLEDs for a 4k display with RGB pixel setup). While the challenges of high resolution and massive parallelization of optical μLED testing has been addressed earlier , color uniformity and hence color accuracy is still a challenge for μLED testing on wafers and in display mass production.
This paper shows how the superior measurement accuracy of spectroradiometers can be extended to the faster optical quality test methods of imaging light measurement devices. This unique combination of advantages satisfies the μLED production requirements for speed and color accuracy at the same time.