Multitouch Pressure Sensing With Soft Optical Time-of-Flight Sensors

This article reports on optical time-of-flight (ToF) as a detection mode for soft optical deformation sensors. In this work, low-cost miniature light detection and ranging (LiDAR) chips recently developed for consumer mobile device applications perform real-time optical reflectometry at cm scales in soft optical waveguide networks. Our methods complement existing work by capturing spatial information that is lost with amplitude-only measurements. We demonstrate its application in a multitouch button system capable of extracting displacement values from soft optical switches with average error in the range of 100–200 microns on 1.75 mm of the switch travel. Because making reliable electronic connections to soft materials is a challenging task, we focus on minimizing connector count. In a tracking application, we find the centroid of an object on a three-point supported plate using three optical pressure switches connected to a single LiDAR sensor.