HaloTouch: Using IR Multi-Path Interference to Support Touch Interactions with General Surfaces

Sensing touch on arbitrary surfaces has long been a goal of ubiquitous computing, but often requires instrumenting the surface. Depth camera-based systems have emerged as a promising solution for minimizing instrumentation, but at the cost of high touch-down detection error rates, high touch latency, and high minimum hover distance, limiting them to basic tasks. We developed HaloTouch, a vision-based system which exploits a multipath interference effect from an off-the-shelf time-of-flight depth camera to enable fast, accurate touch interactions on general surfaces. HaloTouch achieves a 99.2% touch-down detection accuracy across various materials, with a motion-to-photon latency of 150 ms. With a brief (20s) userspecific calibration, HaloTouch supports millimeter-accurate hover sensing as well as continuous pressure sensing. We conducted a user study with 12 participants, including a typing task demonstrating text input at 26.3 AWPM. HaloTouch shows promise for more robust, dynamic touch interactions without instrumenting surfaces or adding hardware to users.