Abstract: By analogy analysis of signal processing and optical information processing, we present a method that the cylindrical wave can be used as a basic element signal to expand light field information. The formula,which optical signal is expanded by the cylindrical wave, is given and the physical meanings of the weight factor are revealed. It is shown that the same result in the far field is obtained by using the cylindrical wave, spherical wave and plane wave as basic element signals.

Key words: single slit diffraction, basic element signal, cylindrical wave