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Posted on December 6, 2018 by  & 

Microdisplay chip paves the way for high-performance smart glasses

A new generation of lightweight smart glasses has become possible with breakthrough optical chip technology which delivers high resolution displays at a quarter of the size and half the weight of conventional virtual reality (VR) headsets. For more information see the IDTechEx report on Augmented, Mixed and Virtual Reality 2017-2027.
Headsets developed under the EU-funded LOMID project "have much higher performance, are smaller, more lightweight and have better resolution than existing virtual reality headsets on the market, but with the same field of view," says project coordinator Uwe Vogel, Director of Microdisplays and Sensors at the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP in Dresden, Germany.
The three-year EUR 4 million project, involving eight institutions and technology companies in five countries, has produced a one-inch screen device called a microdisplay.
"What we achieved was to put a higher number of pixels onto a 1inch (2.54 cm) screen, than in a regular full HDTV (high definition television) which can be 15 to 60 inches diagonally," he explains. "The pixels are tiny and the pixel density very high and we achieved this with low power consumption," he says noting the microdisplay chip consumes less energy than a current state-of-the-art OLED version.
Screen content is refreshed every eight milliseconds which translates to a fast 120 Hertz frame rate, he says. The speed at which an image is renewed is important for immersive VR viewing as low frame rates and flickering images can cause headaches or motion sickness.
Compact headsets designed by project partner LIMBAK, a technology company in Madrid, seamlessly combines two microdisplay chips for each eye, providing a resolution of 4 800 x 1 920 pixels and a wide field view. Full HD is 1 920 x 1 080 pixels.
Assisted vision for the vision-impaired
The project's high-speed video circuitry on a very small chip is being used in glasses for the visually impaired. Project partner Oxford University, "has developed a headset for people with specific vision disabilities such as macular degeneration using this microdisplay," Dr Vogel says.
"Some areas of natural vision might be disturbed at the periphery or the centre, depending on the visual impairment and this is compensated by the device which provides assisted vision, a bit like augmented reality," he explains. The glasses are equipped not just with 2D cameras but also 3D so the viewer can detect depth. "This is important as vision loss typically also comes with diminishing 3D vision."
Such smart glasses can potentially be used for managing disasters in areas of low visibility such as by firefighters in a smoke-filled room. "For professional purposes you need to move around so weight and visual comfort are very important and miniaturisation is key," Dr Vogel says.
The high resolution also makes it easier to recognise faces or read text.
Bendable surface breakthrough
In another breakthrough, the microdisplay chip can be bent onto a curved surface for more design freedom and more compact devices. "Typically for microdisplays now on the market the silicon chip backplane containing the circuitry and sockets is rigid. What was achieved, mainly by project partner CEA-LETI in Grenoble, France, was to bend the one-inch screen microdisplay. This will enable even smaller optics for VR headsets," Dr Vogel says.
Besides moving towards production of the VR headset and assisted vision applications developed under LOMID, French company MICROOLED plans to commercialise the one-inch OLED microdisplay chips, while German partner XFAB Semiconductor Foundries is producing the backplane wafer technology.
Source and top image: CORDIS
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