  A microscope based on the Linnik interferometer was designed, built, and
tested. Two methods were used for interference pattern measurement:
phase-shifting and polarized single-shot methods. The former uses a low
coherence light emitting diode as a light source, providing 10 nm resolution in
the Z direction and diffraction-limited resolution in the X and Y directions.
The second method is insensitive to vibrations and enables observation of
moving objects. The simplicity and low cost of this instrument make it valuable
for a variety of applications.
