Posted on September 17, 2003July 15, 2023 by g15bossCommissioning and aligning the Microfield Exposure Tool (MET), 2003 Commissioning the MET 0.3-NA, two-mirror optic at 13.4-nm wavelength. Shown are [Goldberg, Naulleau, Denham] At high-NA, measurement accuracy is incredibly sensitive to the alignment and geometry. We devised a null-test to provide an absolute measurement of the system geometry for calibration of all other tests. The Foucault Test or (Knife-Edge) test is the easiest to perform, and easiest to interpret. Indepenent of the geometry, the light and dark pattern here reveals the x-derivative of the wavefront error in this moment. The 3rd-order pattern reveals a 4th-order, spherical aberration, which we corrected. Applying our highest-accuracy technique Phase-Shifting Point-Diffraction Interferometry (PS/PDI) was a challenging task since the pinholes were below 15 nm wide and hard to find. We used a real-time holographic feedback approach that we invented, and software I wrote to visualize the data as we aligned the beam. This was a beautiful optic! Shearing interferometry quickly became our favorite approach. Alignment is trivial, the efficiency is high, and the data is easy to analyze. Now, single-grating shearing is used in many beamline applications worldwide.