Posted on August 15, 1998July 16, 2023 by g15bossPhase-shifting Point Diffraction Interferometry (PS/PDI), 1998 We measured a series of EUV Schwarzschild objective lenses of increasing quality, over several years. The lenses were the Berkeley 10x, The Sandia lens, Tinsley A, Tinsley B1, and Tinsley B2. In these tests, we reached diffraction-limited docusing, developed single-grating shearing interferometry, showed flare measurement, holographic imaging, and more. Shown are Paul Denham, Kenneth Goldberg, Patrick Naulleau. The interferometer reached an accuracy of 1/300th of the EUV wavelength, below 50 pm. For this work, Goldberg and Naulleau shared the ALS Halbach Prize for Instrumentation. Goldberg and Naulleau are presented with the award by Werner Meyer-Ilse.