Optical methods for measuring the feature size of optical diffraction gratings with nano-meter accuracy and implementation of suitable feedback control loopsThomas Flügel-Paul, Martin Heusinger, Kristin Gerold, Adriana Szeghalmi and Uwe ZeitnerEPJ Web Conf., 266 (2022) 03008DOI: https://doi.org/10.1051/epjconf/202226603008