Movable micromirrors: German start-up rethinks AR displays

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The start-up Gixel is taking a new approach to building glasses for augmented reality (AR). Instead of further developing existing display technologies such as birdbath optics and waveguides, Gixel relies on movable micromirrors. The displays in the AR glasses project light onto the micromirrors, which are integrated into the lenses of the glasses and reflect the light back into the eye. To ensure that the image is always clearly visible, the mirrors are mechanically aligned along the pupil movement. The movement is recorded using a pupil tracker.

The micromirrors themselves remain virtually invisible as they are embedded in a liquid with an identical refractive index. This means that transparency is largely maintained when looking through them. The design also remains compact, which should make the AR glasses suitable for use in public.

High energy efficiency with an expandable field of vision

Entrepreneur Felix Nienstaedt and the two optics experts and former Fraunhofer engineers Miro Taphanel and Ding Luo founded Gixel in 2019. Driven by the vision of AR-based telepresence, the team presented an experimental AR video conferencing system in 2021.

Since then, the focus has shifted. It is now on the development of an AR display that makes such applications as unobtrusive as possible and usable on the move.

A current prototype already has one of these micromirrors, albeit without pupil tracking. The eye must therefore still be manually adjusted to the optimum position to see the digital overlay. The field of vision is currently limited, but could be expanded by adding more micromirrors, explains CEO Felix Nienstaedt in an interview with heise online. In theory, mirror clustering should make it possible to achieve a field of vision that exceeds that of conventional AR displays, thus eliminating one of the biggest limitations of current systems.

Another advantage of micromirror technology is its high energy efficiency: significantly less light should be lost on the way to the eye than with waveguide displays, which refract and absorb light many times over. Visual artifacts such as color fringing, rainbow effects or ghosting should also be noticeably reduced, says the start-up. Glasses that use the AR display are compatible with corrective lenses.

From proof of concept to product

Even though the prototype does not yet contain all the critical components, it has already attracted the interest of investors. Gixel was able to attract Oculus co-founder Brendan Iribe, Paramount's chief futurist Ted Schilowitz and the founders of Flixbus for seed funding of 5 million euros, which was announced today. In addition, the start-up, which now has 15 employees, has already received funding from the Federal Agency for Springboard Innovations (SPRIND) in 2021.

By the end of the year, a fully functional prototype with three movable micromirrors and integrated pupil tracking is to be created from the previous proof of concept. Gixel intends to use this to approach further investors and potential partners from the tech industry. The start-up is aiming for a further round of investment next year and is already considering the next steps: further miniaturization of the technology and the development of production capacities.

In terms of in-house production, the start-up wants to focus on the central components of its technology: the micromirrors and their control system as well as the projector. Other components such as pupil tracking and the light source can be implemented by the eyewear manufacturers themselves thanks to broad compatibility, allowing them to determine important product properties such as resolution and luminance.

First goal: AI glasses with a Gixel display

In order to keep the technical complexity manageable for the time being, micromirror technology will initially be used in AI glasses with a limited field of vision. Devices with larger mirror clusters will be developed at a later date in line with market demand, explains Marcus Kühne, responsible for strategy and partnerships at Gixel.

It remains to be seen what limitations and problems will arise in the further course of development. Realistically, a miracle solution should not be expected here either. If the history of AR glasses teaches us one thing, it is that there will always be compromises at a technical level. The only question is which ones.

One potential challenge is the visibility of the mirrors in the field of vision. According to Gixel, it is already so low that it is reminiscent of the fine dust that collects on a pair of glasses over the course of the day. The structures that hold and move the micromirrors are also barely perceptible and are being further optimized towards complete transparency. An independent practical test will have to show to what extent they will ultimately prove annoying.

(mma)