Universität Stuttgart
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Item Open Access Farbkodierte objektangepasste Streifenprojektion für die schnelle 2D- und 3D-Qualitätsprüfung(2002) Haist, Tobias; Tiziani, Hans J.Die Kontrolle von Werkstücken hinsichtlich ihrer dreidimensionalen Geometrie und ihrer Oberflächencharakteristik ist von entscheidender Bedeutung für die automatisierte industrielle Produktion. Vorgestellt wird ein schnelles und robustes Einzelbildverfahren das es gestattet, gleichzeitig die Topographie zu kontrollieren und ein Videobild des Werkstückes zu generieren. Hierzu wird eine objektangepasste Streifenprojektion mit einer farbkodierten Maske verwendet. Zur Detektion können preiswerte Einzelchip Farbkameras zum Einsatz kommen. Das Verfahren erzielt eine vergleichsweise gute 3D-Auflösung von 1/4000 bei einer hohen lateralen 2D- und 3D-Auflösung und ist weitgehend unempfindlich gegen lokale Verschmutzungen und Variation der Beleuchtung.Item Open Access Depth from axial differential perspective(2022) Faulhaber, Andreas; Krächan, Clara; Haist, TobiasWe introduce an imaging-based passive on-axis technique for measuring the distance of individual objects in complex scenes. Two axially separated pupil positions acquire images (can be realized simultaneously or sequentially). Based on the difference in magnification for objects within the images, the distance to the objects can be inferred. The method avoids some of the disadvantages of passive triangulation sensors (e.g., correspondence, shadowing), is easy to implement and offers high lateral resolution. Due to the principle of operation it is especially suited for applications requiring only low to medium axial resolution. Theoretical findings, as well as follow-up experimental measurements, show obtainable resolutions in the range of few centimeters for distances of up to several meters.Item Open Access 3D printing of colored micro-optics(2023) Aslani, Valese; Toulouse, Andrea; Schmid, Michael; Giessen, Harald; Haist, Tobias; Herkommer, AloisItem Open Access Field evaluation of a novel holographic single-image depth reconstruction sensor(2023) Hartlieb, Simon; Schober, Christian; Haist, Tobias; Reichelt, StephanItem Open Access 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.Item Open Access 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.