New common-path phase shifting interferometer using a polarization technique

A new type of phase shifting interferometer with a common-path arrangement using a polarization technique is proposed and discussed. In the interferometer, the dc (specular) component of an object beam is separated in the Fourier transform plane and used as a reference beam for its ac component. The phase of the dc component used as the reference beam is shifted by using a polarization technique for phase shifting interferometry. The present interferometer is different from a shearing type in that the phase distribution of an object beam is directly analyzed from the acquired intensity variations obtained by a 2-D detector such as a TV camera. Some experiments were conducted to verify the validity of the present phase shifting interferometer. They showed that high stability of the phase measurements is achieved up to lambda/200 with an accuracy of lambda/40 for wavelength lambda light. The interferometer is suitable for obtaining 2-D phase information about the surface structure of small objects.