REALHOLO – Phase modulating micro mirror array for real holographic mixed-reality displays

The merging of real and virtual worlds to produce mixed reality environments is becoming a realistic component of future society. It demands a natural visual experience without physiological side effects for the user and without limitations in depth perception. Fraunhofer IPMS will contribute to this goal by developing advanced MEMS spatial light modulators as the core component of 3D-displays featuring real holography for perfectly realistic images. The work is based on decades of IPMS experience at developing SLMs for other applications. It is funded by the EU in the H2020 project REALHOLO where a holographic demonstrator system will be developed in an joint effort with 7 other partners from 6 different countries.

The key component of a real holographic 3D display is a spatial light modulator (SLM), and the required properties are quite challenging to reach. The micro mirror array (MMA) SLM modulates the phase of incoming coherent light with many millions of individually deflected pixels at frame rates of several kHz. The pixels have to be only a few micrometers in size and still need to have a stroke range of about 350nm within which each pixel has to be set very precisely to one of many deflection levels. To achieve this, IPMS has developed an innovative micro electro-mechanical system (MEMS) actuator concept with a goal of 8 bit resolution. The MEMS-based SLM will also exhibit optical properties far superior to available liquid crystal-based devices.

Within REALHOLO the IPMS will research and develop this new type of SLM, as well as develop a fabrication technology for it. To be able to deflect all the pixels individually, the MMA will be fabricated on top of an active CMOS mixed signal addressing circuit which will be optimized for very low power consumption and high data bandwidth. With this innovative MEMS SLM Fraunhofer IPMS and REALHOLO will pave the way for mixed reality environments as well as virtual and augmented reality systems. Holographic displays using IPMS micro mirror arrays will provide the best possible experience for the user without physiological side effects like eye fatigue, misjudgement, motion sickness and accommodation-vergence conflict, which are known from alternative and intermediate technologies such as stereoscopic 3D. The required natural visual experience can only be achieved with real holographic displays, which have been principally demonstrated on the basis of available component technologies by a REALHOLO partner.

Fraunhofer IPMS’s newly developed MEMS technology and SLM will also enable many other applications that may benefit from the fast SLM’s precise phase modulation with a large number of pixels. This project is being funded by the European Union’s research and innovation program Horizon 2020 under grant agreement number 101014977. It is an initiative of the Photonics Public Private Partnership.