Fraunhofer FEP bets on quad-OLEDs for healthy VR
To accomodate these OLED microdisplays, the prototype sports ultra-compact optics designed by project partner Limbak, which seamlessly combine two display chips per eye. All four WUXGA microdisplays give the headset a total resolution of 4800×1920 pixels, close to 5k. The new design is said to facilitate very high effective display resolutions and a wide field of view (over 100°) for an excellent immersive VR sensation. This new design aims to solve the challenges encountered by most of today’s commercial VR glasses, often inducing ‘motion sickness’ for the wearer, partly because of low frame rates and image flickering, and partly by an inappropriate field of view.
The latest research results from the European funded project LOMID (Large cost-effective OLED microdisplays and their applications) are expected to solve these challenges: Large-area OLED microdisplays, combined with advanced free-form optics provide an ergonomic and lightweight solution for the design of VR glasses, and higher frame-rates will reduce the motion sickness for users.
The optics scientists of Limbak have been able to decrease the display-to-eye distance needed in the headset, lowering it to only 37mm (compared to 60-75 mm in most conventional headsets). This ultra-compact optical design reduces the headset size to about a quarter of the volume and half the weight of a conventional headset while maintaining the same field of view.
“To offer such high framerates of 120 Hz and thus high data rates, we have extended the parallel interface of the OLED microdisplays. The display mode can be configured flexible from hold-type to impulse-type. The latter allows the elimination of motion artefacts and flicker with a special rolling emission mode. The chip also provides special look-up-tables for gamma correction – each channel (red, green, blue, and white) can be calibrated individually. We achieved a superior image quality with a very high contrast ratio of >100’000 : 1 at extraordinary low power consumption. We are very pleased about these positive results of our displays in combination with the ultra-compact optic design of Limbak, which enable really compact VR devices”, explained Judith Baumgarten, scientist in the IC and System Design department at Fraunhofer FEP.
The tiling of multiple OLED-on-silicon microdisplays inside the system has helped reduce its form factor and weight, while increasing resolution to a level not easily achieved by conventional TFT-based AMOLED displays in VR headsets currently due to their typical pixel density limits.
To keep the costs of manufacturing large-area OLED microdisplays in a reasonable range, LOMID project partner X-FAB developed economical processes at the CMOS silicon foundry, paying special attention to the interface between the top metal electrode of the CMOS backplane and the subsequent OLED layers. Partner Microoled S.A.S. was responsible for the fabrication of the whole OLED microdisplays using the CMOS backplane wafers.
Fraunhofer FEP – www.fep.fraunhofer.de
Related articles:
WUXGA OLED microdisplay promises lightweight and compact VR glasses
European project aims at 2300ppi OLED microdisplays
Electron beam patterning for high-resolution full-colour OLED displays
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