Chemical wave propagation in a two dimensional heterogeneous medium consisting of an inner 'slower' and an outer 'faster' homogeneous medium is studied theoretically and experimentally. The essential features of the evolution of such wave fronts can be derived from the geometrical wave theory based on the Fermat's principle of minimal propagation time. The interfacial boundary is chosen to realize a perfect image formation. This means that circular fronts starting from a given point, after refraction will also be circular, focusing (travelling inwards and converging) into an other point. This way a chemical lens is constructed and realized experimentally. (c) 2005 Elsevier B.V. All rights reserved.