Then, the corners in all images are detected and matched automatically. First, a series of images of the designed marker board at different imaging orientations are captured by the endoscope. The paper proposes a novel method for radial distortion correction using spherical projection model. The goals of this survey are (1) to introduce this research field to a broader audience in the Multimedia community to stimulate further research, (2) to describe domain-specific characteristics of endoscopic videos that need to be addressed in a pre-processing step, and (3) to systematically bring together the very diverse research results for the first time to provide a broader overview of related research that is currently not perceived as belonging together.Īlthough medical endoscopy has been widely used in surgical procedures in clinical practice, radial distortion induced by the small size of the spherical lens in the endoscopic images generally lead to depth perception error and wrong position correlation of human tissues. Many post-processing problems are based on typical Multimedia methods like indexing, retrieval, summarization and video interaction, but have only been sparsely addressed so far for this domain. While most contributions deal with real-time assistance at procedure time, the post-procedural processing of recorded videos is still in its infancy. Proposed works mainly include image processing techniques, pattern recognition, machine learning methods and Computer Vision algorithms. Since then, various research communities with manifold backgrounds have picked up on the idea of processing and automatically analyzing the inherently available video signal that is produced by the endoscopic camera. In recent years, digital endoscopy has established as key technology for medical screenings and minimally invasive surgery. The contributions are highly relevant for applications in computer-aided surgery and image-guided intervention such as improved visualization by image warping, 3-D modeling, and visual SLAM. The system is evaluated for different technical aspects, including accuracy of modeling and calibration, overall robustness, and runtime profile. This enables real-time performance, even for HD video inputs. The workload is distributed across the CPU and GPU through an optimized CPU+GPU hybrid solution. For oblique-viewing endoscopes the changes in calibration during operation are handled by a new adaptive camera projection model and an algorithm that infer the rotation of the probe lens using only image information. The initial camera calibration is performed in an unsupervised manner from a single checkerboard pattern image. Our system can be used with any type of medical endoscopic technology, including oblique-viewing endoscopes and HD image acquisition. This article presents a complete software-based system to calibrate and correct the radial distortion in clinical endoscopy in real time. The small size of the lens causes radial distortion of the image, which hinders the navigation process and leads to errors in depth perception and object morphology. These procedures are renowned for the difficulty of orienting the camera and instruments inside the human body cavities. Medical endoscopy is used in a wide variety of diagnostic and surgical procedures. Therewith, a distortion correction for arbitrary rotation angles and shifts becomes possible without performing static calibrations for every possible combi- nation of shifts and angles beforehand. This enables us to estimate the position of the distortion centre according to the relative movement of camera and optics. For the compensation, we combine a conventional static method for distortion correction with an algorithm to detect the position and the orientation of the elliptic fleld of view. In this paper, we describe an algorithm for the dynamic correction of lens distortion in cystoscopy which is based on a one time calibration. This ∞exibility has a major impact on the location of the distortion centre as it is moved along with the optics. in bladder endoscopy or sinus endoscopy, the camera sensor and the optics do not form a rigid system but they can be shifted and rotated with respect to each other during an examina- tion. In case of endoscopy systems with exchangeable optics, e.g. Endoscopic images are strongly afiected by lens distortion caused by the use of wide angle lenses.
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