A waveguide holographic optical eye-tracking system. Credit: Jianbo Zhao et al., doi 10.1117/1.OE.60.8.085101.
It's all in the eyes. When they view scenes in augmented reality, (AR), they are always on the move.
Developers of AR headsets have been increasingly interested in tracking eye movements with mixed reality systems. This allows system designers to increase image fidelity and contrast across the entire field of view, without putting too much strain on the projection system. This allows for greater battery life and more utility.
Various eye-tracking systems were investigated but none are as precise or bulky. The use of holographic optical elements (HOES), has been proven to be well-suited for AR eyewear. These elements can be made to achieve complex optical functions such as high efficiency in thin films that can either be deposited on flat or curved surfaces. Dichromated gelatin, (DCG), and dry-processed Covestro photospolymers are two promising materials for HOES/AR eyeswear. Near-infrared wavelengths are required for the sensing of AR systems. This is beyond the usual sensitivity ranges of DCG (350-550 nm), and PP materials (405-650 nm). This can cause significant aberrations in the design of elements with focusing power, as the reconstruction wavelength may differ from the construction wavelength.
Researchers from the University of Arizona have created an experimental holographic input-coupling lens using a photopolymer that is deposited on a substrate of 0.6mm thickness. This reduces aberrations caused by the shift in reconstruction wavelength. To increase the field-of-view, a multiplexed out-coupling waveguide HOE with five gratings has been designed and manufactured. Researchers believe that the results show the potential for a holographic eye-tracking system using holographic waveguides. Future work could improve upon this.
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Additional information: Jianbo Zhang et al., Design of a near-infrared waveguide eye-tracking device with holographic optical components, Optical Engineering (2021). Jianbo Zhao and colleagues, Design of a waveguide optical tracking system operating in nearinfrared with integrated holographic elements, (2021). DOI: 10.1117/1.OE.60.8.085101
