@article{VogtKruegerSchmidtetal.2004, author = {Vogt, F. and Kr{\"u}ger, S. and Schmidt, Jochen and Paulus, D. and Niemann, H. and Hohenberger, W. and C. H., Schick}, title = {Light Fields for Minimal Invasive Surgery Using an Endoscope Positioning Robot}, series = {Methods of Information in Medicine}, journal = {Methods of Information in Medicine}, year = {2004}, abstract = {OBJECTIVES: To generate a fast and robust 3-D visualization of the operation site during minimal invasive surgery. METHODS: Light fields are used to model and visualize the 3-D operation site during minimal invasive surgery. An endoscope positioning robot provides the position and orientation of the endoscope. The a priori un-known transformation from the endoscope plug to the endoscope tip (hand-eye transformation) can either be determined by a three-step algorithm, which includes measuring the endoscope length by hand or by using an automatic hand-eye calibration algorithm. Both methods are described in this paper and their respective computation times and accuracies are compared. RESULTS: Light fields were generated during real operations and in the laboratory. The comparison of the two methods to determine the unknown hand-eye transformation was done in the laboratory. The results which are being presented in this paper are: rendered images from the generated light fields, the calculated extrinsic camera parameters and their accuracies with respect to the applied hand-eye calibration method, and computation times. CONCLUSION: Using an endoscope positioning robot and knowing the hand-eye transformation, the fast and robust generation of light fields for minimal invasive surgery is possible.}, language = {en} } @inproceedings{ZinsserSchmidtNiemann2003, author = {Zinßer, T. and Schmidt, Jochen and Niemann, H.}, title = {Performance Analysis of Nearest Neighbor Algorithms for ICP Registration of 3-D Point Sets}, series = {Vision, Modeling, and Visualization 2003}, booktitle = {Vision, Modeling, and Visualization 2003}, year = {2003}, abstract = {There are many nearest neighbor algorithms tailor made for ICP,but most of them require Special input data like range Images or triangle meshes. We focus on efficient nearest neighbor algorithms that do not impose this limitation, and thus can also be used with 3-D point sets generated by structure-frommotion techniques. We shortly present the evaluated algorithms and introduce the modifications we made to improve their efficiency. In particular, several enhancements to the well-known k-D tree algorithm are described. The first part of our Performance Analysis consists of Experiments on synthetic point sets, whereas the second part features experiments with the ICP algorithm on real point sets. Both parts are completed by a thorough evaluation of the obtained results.}, language = {en} } @inproceedings{WenhardtSchmidtNiemann2002, author = {Wenhardt, S. and Schmidt, Jochen and Niemann, H.}, title = {Didaktische Aufbereitung von Methoden des Rechnersehens f{\"u}r virtuelle Vorlesungen}, series = {Forschungsbeitr{\"a}ge zur Didaktik der Informatik - Theorie, Praxis, Evaluation}, booktitle = {Forschungsbeitr{\"a}ge zur Didaktik der Informatik - Theorie, Praxis, Evaluation}, year = {2002}, abstract = {Dieser Artikel stellt ein Konzept f¨ur eine Online-Vorlesung im Rahmen der virtuellen Hochschule Bayern vor. Zun{\"a}chst werden kurz die fachlichen Inhalte erl¨autert, die es zu vermitteln gilt. Nach dieser Einf{\"u}hrung wird auf die Umsetzung der Inhalte in eine dem neuen Medium Internet angemessene Form eingegangen. Dies betrifft vor allem die ausgew{\"a}hlten Techniken, die zur Wissensvermittlung eingesetzt werden. Ein besonderer Schwerpunkt liegt auf der M{\"o}glichkeit durch Interaktivit{\"a}t das Wissen experimentell zu vertiefen und somit eine Verbindung zwischen dem theoretisch Gelernten und dem praktisch Erfahrenen herzustellen. Weiterhin wird eine Vielfalt an Kommunikationsm¨oglichkeiten vorgestellt, da Kommunikation eine wichtige soziale Komponente im Lernprozess und h¨aufig entscheidend f¨ur den Erfolg ist.}, language = {de} } @inproceedings{SchmidtVogtNiemann2002, author = {Schmidt, Jochen and Vogt, F. and Niemann, H.}, title = {Nonlinear Refinement of Camera Parameters using an Endoscopic Surgery Robot}, series = {Proceedings of IAPR Conference on Machine Vision Applications (MVA)}, booktitle = {Proceedings of IAPR Conference on Machine Vision Applications (MVA)}, year = {2002}, abstract = {We present an Approach for non linea roptimization of the parameters of an endoscopic camera mounted on a surgery robot. The goal is to generate a depth map for each image in order to enhance the quality of medical light fields. The pose information provided by the robot is used as an initialization, where especially the orientation isi naccurate. Refinement of intrinsic and extrinsic camera parameters is performed by minimizing the back-projectionerror of 3-D points that are reconstructed by triangulation from image Feature stracked over an image sequence. Optimization of the camera parameters results in an enhancement of Rendering Quality in two ways: More accurate parameters lead to better interpolation as well as to better depth maps for approximating the scenegeometry.}, language = {en} } @inproceedings{SchmidtNiemannVogt2002, author = {Schmidt, Jochen and Niemann, H. and Vogt, F.}, title = {Dense Disparity Maps in Real-Time with an Application to Augmented Reality}, series = {Proceedings Sixth IEEE Workshop on Applications of Computer Vision (WACV 2002), pages 225-230, Orlando, FL USA}, booktitle = {Proceedings Sixth IEEE Workshop on Applications of Computer Vision (WACV 2002), pages 225-230, Orlando, FL USA}, year = {2002}, abstract = {This work presents a technique for computing dense disparity maps from a binocular stereo camera system. The methods are applied in an Augmented Reality setting for combining real and virtual worlds with proper occlusions. The proposed stereo correspondence technique is based oil area matching and facilitates an efficient strategy by using the concept of a three-dimensional similarity accumulator whereby occlusions are detected and object boundaries are extracted correctly. The main contribution of this paper is the way we fill the accumulator using absolute differences of images and computing a mean filter on these difference images. This. is. where the main advantages of the accumulator approach can be exploited, since all entries can be computed in parallel and thus extremely efficient. Additionally, we-perform an asymmetric correction step and a post-processing of the disparity maps that maintains object edges.}, language = {en} } @inproceedings{SchmidtNiemann2002, author = {Schmidt, Jochen and Niemann, H.}, title = {Using Quaternions for Parametrizing 3D Rotations in Unconstrained Nonlinear Optimization}, series = {Vision, Modeling, and Visualization 2001, pages 399-406, Stuttgart, Germany}, booktitle = {Vision, Modeling, and Visualization 2001, pages 399-406, Stuttgart, Germany}, year = {2002}, abstract = {In this paper we address the problem of using quaternions in unconstrained nonlinear optimization of 3-D rotations. Quaternions representing rotations have four elements but only three degrees of freedom, since they must be of norm one. This constraint has to be taken into account when applying e.g. the Levenberg-Marquardt algorithm, a method for unconstrained nonlinear optimization widely used in computer vision. We propose an easy to use method for achieving this. Experiments using our parametrization in photo grammetric b{\"u}ndle -adjustment are presented at the end of the paper.}, language = {en} } @inproceedings{SchmidtScholzNiemann2001, author = {Schmidt, Jochen and Scholz, I. and Niemann, H.}, title = {Placing Arbitrary Objects in a Real Scene Using a Color Cube for Pose Estimation}, series = {Pattern Recognition, 23rd DAGM Symposium}, booktitle = {Pattern Recognition, 23rd DAGM Symposium}, year = {2001}, abstract = {We describe an Augmented Reality system using the corners of a color cube for camera calibration. In the augmented image the cube is replaced by a computer generated virtual object. The cube is localized in an image by the CSC color segmentation algorithm. The camera projection matrix is estimated with a linear method that is followed by a nonlinear refinement step. Because of possible missclassifications of the segmented color regions and the minimum number of point correspondences used for calibration, the estimated pose of the cube may be very erroneous for some frames; therefore we perform outlier detection and treatment for rendering the virtual object in an acceptable manner.}, language = {en} } @inproceedings{ScholzSchmidtNiemann2001, author = {Scholz, I. and Schmidt, Jochen and Niemann, H.}, title = {Farbbildverarbeitung unter Echtzeitbedingungen in der Augmented Reality}, series = {Workshop Farbbildverarbeitung, pages 59-65, Erlangen, Germany, 4.-5. Oktober 2001. Universit{\"a}t Erlangen-N{\"u}rnberg, Institut f{\"u}r Informatik}, booktitle = {Workshop Farbbildverarbeitung, pages 59-65, Erlangen, Germany, 4.-5. Oktober 2001. Universit{\"a}t Erlangen-N{\"u}rnberg, Institut f{\"u}r Informatik}, year = {2001}, abstract = {Es wird ein System aus der Augmented Reality (Erweiterte Reali{\"a}at, AR) vorgestellt, das zur Kamerakalibrierung einen farbigen W{\"u}rfel verwendet, der außerdem als Platzhalter f{\"u}r ein virtuelles Objekt dient. Zur Erkennung des W{\"u}rfels in einer Szene werden Methoden aus der Farbbildverarbeitung verwendet, wie der Color Structure Code (CSC) und die Klassifikation der entstehenden Regionen nach ihrer Farbe. Zur Beschleunigung der Segmentierung wird ein hierarchisches Verfahren eingesetzt.}, language = {de} } @article{SchmidtNiemann2008, author = {Schmidt, Jochen and Niemann, H.}, title = {Data Selection for Hand-eye Calibration: A Vector Quantization Approach}, series = {The International Journal of Robotics Research}, journal = {The International Journal of Robotics Research}, year = {2008}, abstract = {This paper presents new vector quantization based methods for selecting well-suited data for hand-eye calibration from a given sequence of hand and eye movements. Data selection can improve the accuracy of classic hand-eye calibration, and make it possible in the first place in situations where the standard approach of manually selecting positions is inconvenient or even impossible, especially when using continuously recorded data. A variety of methods is proposed, which differ from each other in the dimensionality of the vector quantization compared to the degrees of freedom of the rotation representation, and how the rotation angle is incorporated. The performance of the proposed vector quantization based data selection methods is evaluated using data obtained from a manually moved optical tracking system (hand) and an endoscopic camera (eye).}, language = {en} } @inproceedings{SchmidtVogtNiemann2005, author = {Schmidt, Jochen and Vogt, F. and Niemann, H.}, title = {Calibration-Free Hand-Eye Calibration: A Structure-from-Motion Approach}, series = {Joint Pattern Recognition Symposium}, booktitle = {Joint Pattern Recognition Symposium}, publisher = {Springer}, address = {Berlin}, year = {2005}, abstract = {The paper presents an extended hand-eye calibration approach that, in contrast to the standard method, does not require a calibration pattern for determining camera position and orientation. Instead, a structure-from-motion algorithm is applied for obtaining the eye-data that is necessary for computing the unknown hand-eye transformation. Different ways of extending the standard algorithm are presented, which mainly involves the estimation of a scale factor in addition to rotation and translation. The proposed methods are experimentally compared using data obtained from an optical tracking system that determines the pose of an endoscopic camera. The approach is of special interest in our clinical setup, as the usage of an unsterile calibration pattern is difficult in a sterile environment.}, language = {en} }