Energy-saving data glasses

German researchers have developed an energy-saving display for data glasses, enabling wearers to use them for far longer than would otherwise be possible.

Also known as smart glasses, data glasses include a small display that presents the wearer’s eye with information or images, received using a radio link from the frame of the glasses. These displays also use up a lot of battery power — typically depleting after one hour — as the electronics consume a great amount of electricity while playing back the images. Furthermore, the microprocessors get hot very quickly, causing the frame of the glasses to warm up.

In order to combat these issues, engineers from the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP in Dresden have been working on an energy-saving display that utilises organic light emitting diodes (OLEDs). These are based on electrically conducting organic semiconductors that emit very bright light while energised.

The researchers applied the OLEDs to a silicon semiconductor which controls the individual pixels. They also integrated a camera function into the chip. As a result, the OLED microdisplays not only emit light but also perceive the surroundings, with a small light-sensitive photodiode located in each pixel.

Unfortunately the displays still suffered from high energy consumption as, in order to avoid the flickering of a moving video image, many successive images have to be played in one second, like with a flipbook — in the case of the video display, this amounts to 60 images and eats up a lot of electricity. Project manager Philipp Wartenberg and his colleagues therefore had to find a way to reduce the large data stream.

“We now control the chip so that the entire video image is not constantly renewed, rather only that part of the display in which something changes,” he said. “For example, if an actor runs through a room in a movie, only his position changes, not the background. In applications such as a navigation system for cyclists, in which only arrows or metre information is displayed, it is unnecessary in any case to constantly renew the whole picture.

“To put it simply, we have now adapted the circuit so that it only lets through that portion of the data stream which changes,” said Wartenberg.

While ordinary data glasses require an output of 200 mW, the Fraunhofer FEP display suffices with 2–3 mW, while remaining bright due to the OLED technology. The scientists hope to bring the display to the market soon, with Wartenberg envisioning potential applications in both industry and athletics.

Image ©Fraunhofer FEP. Photographer: Anna Schroll