Another (see 1111) cardboard model made by Dr Norman Heckenberg as an aid to understanding and explaining laser beams with embedded phase singularities. The cardboard surface represents a wavefront in the beam.

The term 'optical leopard' was coined by a theoretical group in Milan to describe a beam with four dark spots. The point is that, due to the complex helical phase structure of the beam, the dark spots are persistent indefinitely and do not diffract away as a dark shadow would. Heckenberg and Dr Carl-Otto Weiss and their students were able to demonstrate lasers producing such beams.