Phase effects in double-focus and double-aperture interference microscopy.

Two different optical techniques for surface tracking and linewidth measurement are evaluated. First, an evaluation is made of the performance of a double-focus polarization microscope, based on results from a computer model and from experimental measurements. The assessment shows that a phase curvature effect makes the operation of this configuration impractical as a surface tracking device and linewidth measurement system. An alternative arrangement of using a double aperture is evaluated. The phase curvature effect is reduced in this type of microscope. A practical optical arrangement to implement a double-aperture microscope is given.