Hinge Power & Data Transfer for AR Glasses

Core Collaborators: Hironobu Kasashima*, Takuya Sasatani**, Tadahiro Kuroda**, Yasuhiro Hayashi**, Mototsugu Hamada**, Yoshihiro Kawahara**

*BOSTON CLUB Co. Ltd.  **The University of Tokyo

Background and Goal

Folding smart glasses typically requires routing cables through the hinges to interconnect sensors and displays. These cables compromise the glasses’ durability and appearance—a challenge that smart glasses have in general. The goal of this work is to make a replacement for physical wiring to lower the barriers for designing smart glasses.

Approach

To eliminate hinge wiring, we embed coils near the hinges to enable wireless power transfer and data communication. Our method safely delivers 2 W at ~50% efficiency and supports a 5 Gbps data rate, sufficient for eyewear that presents images and audio to the user. To make this a practical replacement for physical wiring, we addressed three technical challenges:

• Power delivery: Simulations and measurements verified safe wireless transfer of 2 W suitable for eyewear form factors.

• Data communication: By exploiting the millimeter-scale link at the hinge (rather than meter-scale ranges targeted by Bluetooth), we achieved 93× higher throughput at 1/80th the power, in collaboration with semiconductor researchers (Prof. Kuroda's group).

• Power–data coexistence: We proposed a control method that accounts for circuit-switching time between power and data paths and for time-varying transfer efficiency, ensuring reliable simultaneous operation.

Working across academia and industry—including discussions with eyewear designer Mr. Kasashima (BOSTON CLUB Co. Ltd.)—we established a coil design that preserves the look and robustness expected of glasses while meeting device-level requirements. Thus, our approach is not limited to asEars, but can be applied to higher-power, high-throughput systems (e.g. image-projecting smart glasses). We believe it helps balance power and communication performance with durability and aesthetics, enhancing real-world acceptability.

Impact

• The University of Tokyo President's Award 🏆 (Top 0.06% of all graduates in UTokyo)

• Japanese Patent Granted (number: 2021-129497)

• Some smart glasses companies are interested in using this technology in their products, and we are in discussion.

Acknowledgements

• This work was supported by JST ERATO Grant Number JPMJER1501, Japan.

• We thank Changyo Han, Yoshiaki Narusue, Ryo Takahashi, Takashi Ikeuchi, and Hiromasa Hayashi for their advice on hardware design.

Links

Research Publications

• Coil design for wireless power transfer and communication over hinges of smart glasses, ISWC2020. (first author)

Online media

• Interview on the University of Tokyo President's Award (Japanese)