Anwendung von Wavelet-Filtern in einem optischen Prozessor zur automatischen Fehlererkennung in Interferogrammen

Author(s): G. Wernicke, S. Krüger, F. Kallmeyer, H. Gruber, Wolfgang Osten, D. Kayser, N. Demoli

Abstract:

“Die Wavelet-Transformation hat sich als leistungsfähiges Werkzeug bei der Erkennung von Strukturen mit definierter räumlicher Auflösung erwiesen. Im vorliegenden Aufsatz wird die Filter-Prozedur in der komplexen Ebene nicht nur auf numerische Simulationen erweitert, sondern auch in optischen Experimenten durch einen zweifachen Frequenzebenen-Korrelator angewandt. Hierzu wurden drei räumliche Lichtmodulatoren (SLM) auf der Basis von Twisted-Nematic-Flüssigkristallen verwendet.”

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Publication: tm – Technisches Messen
Issue/Year: tm – Technisches Messen, Volume: 69, Issue: 5, Page 236
DOI: 10.1524/teme.2002.69.5.236

Optical processing for the detection of faults in interferometric patterns

Author(s): Frank Kallmeyer, Sven Krueger, Guenther Wernicke, Hartmut Gruber, Nazif Demoli, Wolfgang Osten, Daniel Kayser

Abstract:

“The detection and classification of faults is a major task for optical nondestructive testing in industrial quality control. Interferometric fringes, obtained by real-time optical measurement methods, contain a large amount of image data with information about possible defect features. This mass of data must be reduced for further evaluation. One possible way is the filtering of these images applying the adaptive wavelet transform. The wavelet transform has been proved to be a capable tool in the detection of structures with definite spatial resolution. In this paper it is shown the extraction and classification of disturbances in interferometric fringe patterns, the application of several wavelet functions with different parameters for the detection of faults, and the combination of wavelet filters for fault classification. Furthermore the implementation of complex valued wavelet filters and correlation filters is shown. We will present an algorithm to classify interferometric fringe patterns. In order to achieve real-time processing a hybrid opto-electronic system with a digital image processing and an optical correlation module is favored. The calculated wavelet filters are implemented into the optical correlator system that is based on liquid-crystal spatial light modulators. So, all discussed items were verified experimentally in the optical setup. ”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE, Vol. 4777, 371 (2002)
DOI: 10.1117/12.472237