title: Design considerations for the absolute testing approach of aspherics using combined diffractive optical elements.
abstract: Aspheric optical surfaces are often tested using diffractive optics as null elements. For precise measurements, the errors caused by the diffractive optical element must be calibrated. Recently, we reported first experimental results of a three position quasi-absolute test for rotationally invariant aspherics by using combined-diffractive optical elements (combo-DOEs). Here we investigate the effects of the DOE substrate errors on the proposed calibration procedure and present a set of criteria for designing an optimized combo-DOE. It is demonstrated that this optimized design enhances the overall consistency of the procedure. Furthermore, the rotationally varying part of the surface deviations is compared with the rotationally varying deviations obtained by an N-position averaging procedure and is found to be in good agreement.
authors: Institute of Optics, Information and Photonics (Max-Planck Research Group), Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany. gkhan@optik.uni-erlangen.de
authors: Gufran S
authors: GS
authors: Khan
authors: Klaus
authors: K
authors: Mantel
authors: Irina
authors: I
authors: Harder
authors: Norbert
authors: N
authors: Lindlein
authors: Johannes
authors: J
authors: Schwider