Sinusoidal phase-modulating Fizeau interferometer using a self-pumped phase conjugator for surface profile measurements

A sinusoidal phase-modulating Fizeau interlerometer using a BaTiO₃ self-pumped phase conjugator is constructed to measure surface profiles of objects with a high accuracy. An object field is formed on a surface of a glass plate where the object wave interferes with its phase conjugate wave. Because the size of the glass plate can be much smaller than that of the object, the sinusoidal phase modulation by vibrating the glass plate is easy and accurate for measurements of the surface profiles of large-diameter objects. The interferometer is self-referencing and free of the phase fluctuations of the object wave caused by spatially uniform movements of objects. The usefulness of the interferometer is made clear through the surface profile measurements of a diamond-turned aluminum disk and mirror.