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Combining gradient ascent search and support vector machines for effective autofocus of a field emission–scanning electron microscope

Dembélé, Sounkalo and Lehmann, Olivier and Medjaher, Kamal and Marturi, Naresh and Piat, Nadine Combining gradient ascent search and support vector machines for effective autofocus of a field emission–scanning electron microscope. (2016) Journal of Microscopy, 264 (1). 1-9. ISSN 0022-2720

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Official URL: https://doi.org/10.1111/jmi.12419

Abstract

Autofocus is an important issue in electron microscopy, particularly at high magnification. It consists in searching for sharp image of a specimen, that is corresponding to the peak of focus. The paper presents a machine learning solution to this issue. From seven focus measures, support vector machines fitting is used to compute the peak with an initial guess obtained from a gradient ascent search, that is search in the direction of higher gradient of focus. The solution is implemented on a Carl Zeiss Auriga FE-SEM with a three benchmark specimen and magnification ranging from x300 to x160 000. Based on regularized nonlinear least squares optimization, the solution overtakes the literature non-regularized search and Fibonacci search methods: accuracy improvement ranges from 1.25 to 8 times, fidelity improvement ranges from 1.6 to 28 times, and speed improvement ranges from 1.5 to 4 times. Moreover, the solution is practical by requiring only an off-line easy automatic train with cross-validation of the support vector machines.

Item Type:Article
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Other partners > Ecole Nationale Supérieure de Mécanique et des Microtechniques - ENSMM (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Other partners > Université de Franche-Comté (FRANCE)
Other partners > Université de Technologie de Belfort-Montbéliard - UTBM (FRANCE)
Other partners > Université Bourgogne Franche-Comté - UBFC (FRANCE)
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Deposited On:13 Feb 2019 10:48

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