Abstract: An inteferometer is provided with a light source forming a first collimated beam shaped to illuminate an area and a second collimated beam shaped to illuminate a narrow line. Both of these beams are split into orthogonally-polarized sub-beams, which are diverted outward and inward within a compound Wollastom prism. The images of these beams are focussed on a test surface through an objective lens, with a real splitting point being projected to the rear focal plane of the objective lens. With light reflected off the test surface and projected back through the compound Wollastom prism, interference patterns are generated on the surface of a line sensor, which is typically used with illuminated narrow lines split by the compound prism and projected onto a moving test surface, and on the surface of an area sensor, which is typically used with area illumination projected onto a stationary test surface. Autofocus and automatic phase angle correction servomechanisms are also provided within the interferometer.