TY - JOUR A1 - Vogt, F. A1 - Krüger, S. A1 - Schmidt, Jochen A1 - Paulus, D. A1 - Niemann, H. A1 - Hohenberger, W. A1 - C. H., Schick T1 - Light Fields for Minimal Invasive Surgery Using an Endoscope Positioning Robot JF - Methods of Information in Medicine N2 - 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. KW - Robotics Y1 - 2004 ER - TY - CHAP A1 - Zinßer, T. A1 - Schmidt, Jochen A1 - Niemann, H. T1 - Performance Analysis of Nearest Neighbor Algorithms for ICP Registration of 3-D Point Sets T2 - Vision, Modeling, and Visualization 2003 N2 - 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. KW - ICP Algorithm KW - 3D Point-Sets Y1 - 2003 ER - TY - CHAP A1 - Wenhardt, S. A1 - Schmidt, Jochen A1 - Niemann, H. T1 - Didaktische Aufbereitung von Methoden des Rechnersehens für virtuelle Vorlesungen T2 - Forschungsbeiträge zur Didaktik der Informatik - Theorie, Praxis, Evaluation N2 - Dieser Artikel stellt ein Konzept f¨ur eine Online-Vorlesung im Rahmen der virtuellen Hochschule Bayern vor. Zunächst werden kurz die fachlichen Inhalte erl¨autert, die es zu vermitteln gilt. Nach dieser Einführung wird auf die Umsetzung der Inhalte in eine dem neuen Medium Internet angemessene Form eingegangen. Dies betrifft vor allem die ausgewählten Techniken, die zur Wissensvermittlung eingesetzt werden. Ein besonderer Schwerpunkt liegt auf der Möglichkeit durch Interaktivität 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. KW - Rechnersehen KW - virtuelle Vorlesung KW - Didaktik Y1 - 2002 ER - TY - CHAP A1 - Schmidt, Jochen A1 - Vogt, F. A1 - Niemann, H. T1 - Nonlinear Refinement of Camera Parameters using an Endoscopic Surgery Robot T2 - Proceedings of IAPR Conference on Machine Vision Applications (MVA) N2 - 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. KW - Endoscopic Surgery Robot KW - endoscopic camera KW - minimalinvasive surgery Y1 - 2018 ER - TY - CHAP A1 - Schmidt, Jochen A1 - Niemann, H. A1 - Vogt, F. T1 - Dense Disparity Maps in Real-Time with an Application to Augmented Reality T2 - Proceedings Sixth IEEE Workshop on Applications of Computer Vision (WACV 2002), pages 225-230, Orlando, FL USA N2 - 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. KW - Augmented Reality (AR) KW - Layout KW - Camera KW - Real time systems Y1 - 2018 ER - TY - CHAP A1 - Schmidt, Jochen A1 - Niemann, H. T1 - Using Quaternions for Parametrizing 3D Rotations in Unconstrained Nonlinear Optimization T2 - Vision, Modeling, and Visualization 2001, pages 399-406, Stuttgart, Germany N2 - 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 bündle -adjustment are presented at the end of the paper. KW - 3D Rotations KW - Pattern recognition KW - Unconstrained NonlinearOptimization Y1 - 2002 ER - TY - CHAP A1 - Schmidt, Jochen A1 - Scholz, I. A1 - Niemann, H. T1 - Placing Arbitrary Objects in a Real Scene Using a Color Cube for Pose Estimation T2 - Pattern Recognition, 23rd DAGM Symposium N2 - 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. KW - Augmented Reality (AR) KW - Camera calibration KW - Color segmentation Y1 - 2001 ER - TY - CHAP A1 - Scholz, I. A1 - Schmidt, Jochen A1 - Niemann, H. T1 - Farbbildverarbeitung unter Echtzeitbedingungen in der Augmented Reality T2 - Workshop Farbbildverarbeitung, pages 59-65, Erlangen, Germany, 4.-5. Oktober 2001. Universität Erlangen-Nürnberg, Institut für Informatik N2 - Es wird ein System aus der Augmented Reality (Erweiterte Realiäat, AR) vorgestellt, das zur Kamerakalibrierung einen farbigen Würfel verwendet, der außerdem als Platzhalter für ein virtuelles Objekt dient. Zur Erkennung des Würfels 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. KW - Augmented Reality (AR) KW - Farbsegmentierung Y1 - 2001 ER - TY - JOUR A1 - Schmidt, Jochen A1 - Niemann, H. T1 - Data Selection for Hand-eye Calibration: A Vector Quantization Approach JF - The International Journal of Robotics Research N2 - 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). KW - hand- eye calibration KW - vektor quantization Y1 - 2018 ER - TY - CHAP A1 - Schmidt, Jochen A1 - Vogt, F. A1 - Niemann, H. T1 - Calibration-Free Hand-Eye Calibration: A Structure-from-Motion Approach T2 - Joint Pattern Recognition Symposium N2 - 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. KW - Translation Vector KW - Feature Tracking KW - World Coordinate System KW - Dual Quaternion Y1 - 2005 PB - Springer CY - Berlin ER - TY - CHAP A1 - Zinßler, T. A1 - Schmidt, Jochen A1 - Niemann, H. T1 - Point Set Registration with Integrated Scale Estimation T2 - Proceedings of the Eighth International Conference on Pattern Recognition and Image Processing (PRIP 2005), pages 116-119, Minsk, Republic of Belarus N2 - Wepresentaniterativeregistrationalgorithmfor aligning two differently scaled 3-D point sets. It extends the popular Iterative Closest Point (ICP) algorithm by estimating a scale factor between the two point sets in every iteration. The presented algorithm is especially useful for the registration of point sets generated by structure-frommotion algorithms, which only reconstruct the 3-D structure of a scene upto scale. LiketheoriginalICPalgorithm,thepresentedalgorithm requires a rough pre-alignment of the point sets. In order to determine the necessary accuracy of the pre-alignment, wehaveexperimentallyevaluatedthebasinofconvergence of the algorithm with respect to the initial rotation, translation, andscale factor between the two point sets. KW - Iterative Closest Point KW - Scale Estimation Y1 - 2005 ER - TY - CHAP A1 - Schmidt, Jochen A1 - Vogt, F. A1 - Niemann, H. T1 - Vector Quantization Based Data Selection for Hand-Eye Calibration T2 - Vision, Modeling, and Visualization 2004, pages 21-28, Stanford, USA N2 - The paper presents a new vectorquantization based Approach for selecting well-suited data for hand-eye calibration from a given sequence of hand and eye movements. Data selection is essential if control of the movements used for calibration is not possible, especially when using continuously recorded data. The new algorithm is compared to another method for data selection as well as to the processing of subsequent movements. Experimental results on real and synthetic data sets show the superior performance of the new approach with respect to calibration errors and computation time. Real data has been obtained from an optical tracking system and a camera mounted on an endoscope, the goal being the reconstruction of medical lightfields. KW - Vector Quantization KW - Hand-Eye Calibration KW - Data selection Y1 - 2005 ER - TY - CHAP A1 - Schmidt, Jochen A1 - Vogt, F. A1 - Niemann, H. T1 - Robust Hand-Eye Calibration of an Endoscopic Surgery Robot Using Dual Quaternions T2 - Pattern Recognition, Proceedings of the 25th DAGM Symposium, Magdeburg N2 - This paper presents an approach for applying a dual quaternion hand–eye calibration algorithm on an endoscopic surgery robot. Special focus is on robustness, since the error of position and orientation data provided by the robot can be large depending on the movement actually executed. Another inherent problem to all hand–eye calibration methods is that non–parallel rotation axes must be used; otherwise, the calibration will fail. Thus we propose a method for increasing the numerical stability by selecting an optimal set of relative movements from the recorded sequence. Experimental evaluation shows the error in the estimated transformation when using well–suited and ill–suited data. Additionally, we show how a RANSAC approach can be used for eliminating the erroneous robot data from the selected movements. KW - Pattern Recognition KW - Temporal Orderr KW - Numerical Stability KW - Dual Quaternion  KW - Calibration Pattern  Y1 - 2018 ER - TY - CHAP A1 - Zinßer, T. A1 - Schmidt, Jochen A1 - Niemann, H. T1 - A Refined ICP Algorithm for Robust 3-D Correspondence Estimation T2 - Proceedings of the IEEE International Conference on Image Processing, volume 2, pages 695-698, Barcelona, Spain N2 - Robust registration of two 3-D point sets is a common problem in computer vision. The iterative closest point (ICP) algorithm is undoubtedly the most popular algorithm for solving this kind of problem. In this paper, we present the Picky ICP algorithm, which has been created by merging several extensions of the standard ICP algorithm, thus improving its robustness and computation time. Using pure 3-D point sets as input data, we do not consider additional information like point color or neighborhood relations. In addition to the standard ICP algorithm and the Picky ICP algorithm proposed in this paper, a robust algorithm due to Masuda and Yokoya and the RICP algorithm by Trucco et al. are evaluated. We have experimentally determined the basin of convergence, robustness to noise and outliers, and computation time of these four ICP based algorithms KW - Iterative closest point algorithm KW - Iterative algorithms KW - Noise robustnes KW - Computer vision Y1 - 2003 ER -