Transmissive absolute testing of aspherics using diffractive nulls

The interferometric technique of testing aspherical components with diffractive nulls in reflection is well established. Calibration methods providing an absolute test for aspheric surfaces are derived from the well introduced testing methods of spherical surfaces. However, setups in reflection suffer from disturbing diffraction orders and reflections. Recently (2007) we proposed a calibration method for the absolute testing of aspheric lenses in transmissive light. Apart from reducing back reflections and avoiding disturbing diffraction orders, the spatial frequency content of the diffractive null can also be highly reduced. The presented method allows a highly accurate measurement of the deviation between the wavefront generated by the real optical element and the ideal aspheric wavefront. In this work, the procedure is described in detail and some first results are shown.