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.