Optimising the legibility of symbol signs.

Both the logic underlying the recursive blur technique for optimising the legibility of symbol signs and the computer algorithms for implementing the technique are based upon 2-dimensional (2D) Fourier analysis. The use of 2D-Fourier analysis for the description of complex spatial structures (such as highway signs) is introduced in this paper. This framework is extended to show how 2D-Fourier techniques can be used to "filter-out" specific structural components from a sign stimulus and how this filtering approach has been employed to engineer highway signs with improved legibility.