Variable phase stop for use in interferometers

DETAILED DESCRIPTION In view of the foregoing, there is a need for a dynamically variable phase stop whose characteristics can be electrically controlled.
In such manner, the phase stop can be used in common-path interferometers to provide an adaptive system that can optimize fringe visibility for a wide class of objects of interest.
According to the present invention, a phase stop is provided by way of an electro-optical device through which a light beam of interest is directed.
Means are provided on the electro-optical material to shift the phase of a portion of light with respect to the remainder of the beam passing through the device.
In the preferred embodiment, a plurality of concentric transparent electrodes on one face of the device are used to define the aperture size of the phase stop.
The present invention finds particular utility in a common-path interferometer having a feed back loop designed to selectively energize a given electrode or a set of electrodes to optimize the fringe visibility of the object being analyzed.