An interferometer is described which allows the fast test of acylindrical microlenses at grazing incidence. The interferometer uses two diffractive optical elements as beam splitters and beam shapers For the test of cylinder lenses at grazing incidence a conical test wavefront is needed, which is generated by diffraction at a phase structure. One main feature is that the sensitivity only depends on the pitch of the diffractive elements. The interferometer, the fringe evaluation method, and the method to eliminate aberrations are described in detail and measurement results are presented.