Fingertip Pulse-Echo Ultrasound and Optoacoustic Dual-Modal and Dual Sensing Mechanisms Near-Distance Sensor for Ranging and Material Sensing in Robotic Grasping *

To improve robotic grasping, we are interested in developing a new non-contact fingertip-mounted sensor for near-distance ranging and material sensing. Here we report new progress in combining direct pulse-echo ultrasound and optoacoustic effects in sensor design to deal with optically and/or acoustically challenging targets (OACTs). Our dual-modal and dual sensing mechanisms (DMDSM) sensor design is enabled by a novel wideband ultrasound transmitter embedded inside a piezoelectric (lead zirconate titanate - PZT) ring transducer. The new DMDSM sensor is capable of differentiating a variety of OACTs. To verify our design, both distance ranging tests and material sensing tests have been conducted. The ranging tests show the sensor can perform both optoacoustic ranging (for light-absorbing materials) and pulse-echo ultrasound ranging (for reflective or transparent materials). For material sensing, the dual-modal spectra from OACTs are collected to compare the new sensor with previous designs. The overall 100% accuracy from the confusion matrices indicates the initial success of our sensor design in differentiating conventional targets as well as the OACTs with the new DMDSM sensor.