A Video Speed Tactile Camera

Abstract

A tactile image sensor is described that applies piezoelectric films of PVDF (polyvinylidene fluoride) to map a 2dimensional pressure distribution. The sensor consists of two layers of PVDF. One layer is used to generate, the other layer to sense acoustical vibration. Driven at fixed frequency the configuration can locally switch between resonance and non-resonance at a change of the acoustical impedance of the surrounding media. An object is detected as a blob of locally deviating acoustical impedance. The spatial distribution of acoustical impedance is resolved by linewise driving and columnwise sensing. Application of pressure impedance converters makes the sensor pressure sensitive. Measurements on an experimental tactile image sensor with nine elements are discussed. These experiments have shown that for a tactile image sensor with a binary response a spatial resolution of at least 25 elements per cm² can be realized. The acoustical frequency is sufficiently high to allow video-speed electronic read-out of the detected amplitudes.