For use with optical flats or optical parallels to measure both the flatness and parallelism of the measuring faces by interferometry.
Monochromatic light source providing high-contrast interference fringes.
This light unit uses a single wavelength so that bright/light fringes only are visible.
The light source at the rear of the vase also permits a visual examination, e.g. with the aid of a knife-edge or bevelled straight edge.