The unique properties of the interference field produced by three plane wave interference and their meaning for optical vortex interferometer

The optical vortices are stable phase structures in the wavefront, which posses the characteristic isolated singularity in phase distribution (vortex points). Such singular points can be effectively located and traced (while mowing, for example). Being just point like stable structures they can be used in optical metrology. The optical vortex interferometer (OVI) is the most promising, new measurement instrument working with optical vortices. The OVI is based on the regular net of optical vortices generated by three plane wave interference. At the first sight it looks like a simple extension of the classical two beam interferometry; however this is not a case. The case of three plane waves is very special and the resulting interference field posses a number of unique properties, which are not present if the case of two, four, five or more waves interference field. These special properties become obvious when the behavior of optical vortices seeded in such interference field is analyzed. This presentation is focused on the unique properties of the wave field obtained by three plane wave interference. The resulting advantages for the OVI are briefly shown.