Grazing incidence interferometry applied to the measurement of cylindrical surfaces

Usually, rough surfaces cannot be measured by interferometric methods because the wavefronts are disturbed by speckle noise. This problem can be overcome by an increase of the test wavelength. One way to increase the effective wavelength is to use grazing incidence interferometry. We suggest an interferometer specifically adapted for the measurement of cylinders or tubes. Reference and object wavefront are generated using problem-specific computer-generated holograms as beamsplitters. The method can be extended to other geometries. We introduce the principle and show first experimental results.