Common-path interferometer

A common path interferometer is class of interferometer that does not split the beam into a reference arm and a sample arm. An example is the point diffraction interferometer and zernike phase contrast interferometer. They are generally more resilient to environmental vibrations and can some times be used when no reference beam is available, however the interfence pattern can be more complicated to interpretate than in an amplitude splitting interferometer such as a Mach-Zehnder interferometer