Touch determination by tomographic reconstruction

Abstract

A touch-sensitive apparatus comprises a panel configured to conduct signals from a plurality of peripheral incoupling points to a plurality of peripheral outcoupling points. Actual detection lines are defined between pairs of incoupling and outcoupling points to extend across a surface portion of the panel. The signals may be in the form of light, and objects touching the surface portion may affect the light via frustrated total internal reflection (FTIR). A signal generator is coupled to the incoupling points to generate the signals, and a signal detector is coupled to the outcoupling points to generate an output signal. A data processor operates on the output signal to enable identification of touching objects. The output signal is processed () to generate a set of data samples, which are indicative of detected energy for at least a subset of the actual detection lines. The set of data samples is processed () to generate a set of matched samples, which are indicative of estimated detected energy for fictitious detection lines that have a location on the surface portion that matches a standard geometry for tomographic reconstruction. The set of matched samples is processed () by tomographic reconstruction to generate data indicative of a distribution of an energy-related parameter within at least part of the surface portion.