{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:24:05Z","timestamp":1760239445082,"version":"build-2065373602"},"reference-count":41,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2020,11,10]],"date-time":"2020-11-10T00:00:00Z","timestamp":1604966400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Wavefront analysis is a fast and reliable technique for the alignment and characterization of optics in the visible, but also in the extreme ultraviolet (EUV) and X-ray regions. However, the technique poses a number of challenges when used for optical systems with numerical apertures (NA) &gt; 0.1. A high-numerical-aperture Hartmann wavefront sensor was employed at the free electron laser FLASH for the characterization of a Schwarzschild objective. These are widely used in EUV to achieve very small foci, particularly for photolithography. For this purpose, Schwarzschild objectives require highly precise alignment. The phase measurements acquired with the wavefront sensor were analyzed employing two different methods, namely, the classical calculation of centroid positions and Fourier demodulation. Results from both approaches agree in terms of wavefront maps with negligible degree of discrepancy.<\/jats:p>","DOI":"10.3390\/s20226426","type":"journal-article","created":{"date-parts":[[2020,11,10]],"date-time":"2020-11-10T14:10:41Z","timestamp":1605017441000},"page":"6426","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Wavefront Sensing for Evaluation of Extreme Ultraviolet Microscopy"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7206-6557","authenticated-orcid":false,"given":"Mabel","family":"Ruiz-Lopez","sequence":"first","affiliation":[{"name":"Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg, Germany"}]},{"given":"Masoud","family":"Mehrjoo","sequence":"additional","affiliation":[{"name":"Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg, Germany"}]},{"given":"Barbara","family":"Keitel","sequence":"additional","affiliation":[{"name":"Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg, Germany"}]},{"given":"Elke","family":"Pl\u00f6njes","sequence":"additional","affiliation":[{"name":"Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg, Germany"}]},{"given":"Domenico","family":"Alj","sequence":"additional","affiliation":[{"name":"CNRS, Ecole Polytechique-IPP, ENSTA, Chemin de la Huni\u00e8re, 91761 Palaiseau, France"}]},{"given":"Guillaume","family":"Dovillaire","sequence":"additional","affiliation":[{"name":"Imagine Optic, 18 Rue Charles de Gaulle, 91400 Orsay, France"}]},{"given":"Lu","family":"Li","sequence":"additional","affiliation":[{"name":"Center for Advanced Material Diagnostic Technology, Shenzhen Technology University, Shenzhen 518118, China"}]},{"given":"Philippe","family":"Zeitoun","sequence":"additional","affiliation":[{"name":"CNRS, Ecole Polytechique-IPP, ENSTA, Chemin de la Huni\u00e8re, 91761 Palaiseau, France"}]}],"member":"1968","published-online":{"date-parts":[[2020,11,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1002\/pat.662","article-title":"Recent progress in high resolution lithography","volume":"17","author":"Bratton","year":"2006","journal-title":"Polym. 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