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Author: search.filters.author.Haist, TobiasEnd date: 1999Institute: search.filters.UBSInstitut.Institut für Technische Optik

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Now showing 1 - 4 of 4
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    3D-Linienraster für die optische Formaufzeichnung
    (1996) Haist, Tobias
    Innerhalb der optischen Messtechnik ist es oft nötig, Intensitätsmuster auf die zu vermessenden Objekte zu projizieren. Mit herkömmlichen Abbildungen ergeben sich bei sehr tiefen Objekten Probleme aufgrund der begrenzten Tiefenschärfe. Holographische Projektionen umgehen diese Einschränkung. In der Arbeit wird untersucht, in wieweit computergenerierte Hologramme basierend auf Flüssigkristall-Displays (LCD) für diesen Zweck eingesetzt werden können. Unterschiedliche Algorithmen und LCDs werden untersucht. Eine dreidimensionale Verallgemeinerung des Gerchberg-Saxton-Algorithmus wird dargestellt. Simulationen zur Nutzung der geometrischen Phase (Pancharatnam Phase) um die Phasenmodulationseigenschaften der LCDs zu verbessern werden beschrieben.
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    Optical detection of random features for high security applications
    (1998) Haist, Tobias; Tiziani, Hans J.
    Optical detection of random features in combination with digital signatures based on public key codes in order to recognise counterfeit objects will be discussed. Without applying expensive production techniques objects are protected against counterfeiting. Verification is done offline by optical means without a central authority. The method is applied for protecting banknotes. Experimental results for this application are presented. The method is also applicable for identity verification of a credit- or chip-card holder.
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    Positioning of noncooperative objects using joint transform correlation combined with fringe projection
    (1998) Haist, Tobias; Schönleber, Martin; Tiziani, Hans J.
    Automated assembly and quality control require reliable systems for the detection of the position and orientation of complicated objects. Correlation methods are well suited, but they are affected by structured backgrounds, varying illumination conditions, and textured or dirty object surfaces. Using fringe projection to exploit the three-dimensional topography of objects, we improve the performance of a nonlinear joint transform correlator. Positioning of noncooperative objects with subpixel accuracy is demonstrated. Additionally, the tilt angle of an arbitrarily shaped object is measured by projecting object-adapted fringes that produce a homogeneous fringe pattern in the image plane. An accuracy of better than one degree is achieved.
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    Iterative nonlinear joint transform correlation for the detection of objects in cluttered scenes
    (1999) Haist, Tobias; Tiziani, Hans J.
    An iterative correlation technique with digital image processing in the feedback loop for the detection of small objects in cluttered scenes is proposed. A scanning aperture is combined with the method in order to improve the immunity against noise and clutter. Multiple reference objects or different views of one object are processed in parallel. We demonstrate the method by detecting a noisy and distorted face in a crowd with a nonlinear joint transform correlator.