Recognition of Cuneiform Inscription Signs by use of a Hybrid-Optoelectronic Correlator Device

Author(s): Nazif Demoli, Jörn Kamps, Sven Krüger, Hartmut Gruber, and Günther Wernicke

Abstract:

“A hybrid-optoelectronic correlator device and an algorithm are proposed for recognizing cuneiform inscription signs. The device is based on the extended correlator architecture with three liquid-crystal display(s) (LCD)s and three light detectors: one CCD camera for capturing the input image, one LCD for displaying the input image, two LCDs for the complex correlation filter (amplitude and phase parts), and two detectors for measuring the total and peak intensities of the output correlation information. The recognition algorithm is designed to allow automatic as well as real-time processing. The recognition results are given for the cuneiform signs impressed on an original clay tablet. The investigated tablet (VAT 12890 of the Pergamon Museum, Berlin, Germany) was found in Bogazköy (Hattusha) and dates from the 14th century B.C. It is a fragment of the Epic of Gilgamesh in the Akkadian language with a large number of the sign samples.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 41, Issue 23, pp. 4762-4774, 2002
DOI: 10.1364/AO.41.004762

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

Optimization in mapping of correlation filters in a liquid crystal display based frequency plane correlator

Author(s): Alexander Hirsch, Sven Krüger, Günther Wernicke, Hartmut Gruber, and Mathias Senoner

Abstract:

“An optimization procedure for the optical implementation of correlation filters (CFs) in an optical-hybrid frequency plane correlator is presented. Our approach is based on mapping of the given calculated CF values to the values constrained by the available spatial light modulator (SLM) device to achieve the maximum intensity of the output correlation peak. The optimization is provided for the implementation of the CFs using a Sanyo liquid crystal display (SLCD). The commercially available SLCDs are characterized by the phase modulation curves that are (1) nonlinear, (2) of a smaller total phase change interval than desired (0,2 pi) interval, and (3) significantly disturbed by the coupled amplitude variations. For such a case, the optimization achieved by varying a phase shift parameter is explained theoretically, demonstrated numerically, and confirmed experimentally.”

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Publication: SPIE Optical Engineering
Issue/Year: Opt. Eng., Vol. 38, 1058 (1999);
DOI: 10.1117/1.602150
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