AXICON-TYPE TEST INTERFEROMETER FOR CYLINDRICAL SURFACES

A grazing incidence interferometer using computer generated diffractiv e axicon elements as beam splitter and recombiner can be applied for t he testing of cylindrical surfaces. The interferometer provides a redu ced sensitivity due to grazing incidence and allows the measurement of deviations from the cylindrical form in a single step on the whole su rface of the test piece. The evaluation of the fringe pattern can be c arried out using phase shifting interferometry whereby the necessary p hase shifts can be introduced by small axial shifts of one of the axic ons. In order to extract pure surface deviations from the interferomet er data. we give a theoretical analysis of phase terms belonging to th e stale of adjustment of the test sample relative to the interferometr ic setup. Finally, we discuss a method for the elimination of those ph ase terms.