Stereo Matching in the Presence of Sub-Pixel Calibration Errors

Stereo matching commonly requires rectified images that are computed from calibrated cameras. Since all under-lying parametric camera models are only approximations, calibration and rectification will never be perfect. Additionally, it is very hard to keep the calibration perfectly stable in application scenarios with large temperature changes and vibrations. We show that even small calibration errors of a quarter of a pixel are severely amplified on certain structures. We discuss a robotics and a driver assistance example where sub-pixel calibration errors cause severe problems. We propose a filter solution based on signal theory that removes critical structures and makes stereo algorithms less sensitive to calibration errors. Our approach does not aim to correct decalibration, but rather to avoid amplifications and mismatches. Experiments on ten stereo pairs with ground truth and simulated decalibrations as well as images from robotics and driver assistance scenarios demonstrate the success and limitations of our solution that can be combined with any stereo method

Towards an Autonomous Walking Robot for Planetary Surfaces

In this paper, recent progress in the development of the DLR Crawler - a six-legged, actively compliant walking robot prototype - is presented. The robot implements a walking layer with a simple tripod and a more complex biologically inspired gait. Using a variety of proprioceptive sensors, different reflexes for reactively crossing obstacles within the walking height are realised. On top of the walking layer, a navigation layer provides the ability to autonomously navigate to a predefined goal point in unknown rough terrain using a stereo camera. A model of the environment is created, the terrain traversability is estimated and an optimal path is planned. The difficulty of the path can be influenced by behavioral parameters. Motion commands are sent to the walking layer and the gait pattern is switched according to the estimated terrain difficulty. The interaction between walking layer and navigation layer was tested in different experimental setups

Stereo-vision-based navigation of a six-legged walking robot in unknown rough terrain

In this paper we presents a visual navigation algorithm for the six-legged walking robot DLR Crawler in rough terrain. The algorithm is based on stereo images from which depth images are computed using the semi- global matching (SGM) method. Further, a visual odometry is calculated along with an error measure. Pose estimates are obtained by fusing iner- tial data with relative leg odometry and visual odometry measurements using an indirect information filter. The visual odometry error measure is used in the filtering process to put lower weights on erroneous visual odometry data, hence, improving the robustness of pose estimation. From the estimated poses and the depth images, a dense digital terrain map is created by applying the locus method. The traversability of the terrain is estimated by a plane fitting approach and paths are planned using a D* Lite planner taking the traversability of the terrain and the current motion capabilities of the robot into account. Motion commands and the traversability measures of the upcoming terrain are sent to the walking layer of the robot so that it can choose an appropriate gait for the terrain. Experimental results show the accuracy of the navigation algorithm and its robustness against visual disturbances

The effect of foot orthoses with forefoot cushioning or metatarsal pad on forefoot peak plantar pressure in running.

Background Foot orthoses are frequently used in sports for the treatment of overuse complaints with sufficient evidence available for certain foot-related overuse pathologies like plantar fasciitis, rheumatoid arthritis and foot pain (e.g., metatarsalgia). One important aim is to reduce plantar pressure under prominent areas like metatarsal heads. For the forefoot region, mainly two common strategies exist: metatarsal pad (MP) and forefoot cushioning (FC). The aim of this study was to evaluate which of these orthosis concepts is superior in reducing plantar pressure in the forefoot during running. Methods Twenty-three (13 female, 10 male) asymptomatic runners participated in this cross-sectional experimental trial. Participants ran in a randomised order under the two experimental (MP, FC) conditions and a control (C) condition on a treadmill (2.78 ms−1) for 2 min, respectively. Plantar pressure was measured with the in-shoe plantar pressure measurement device pedar-x®-System and mean peak pressure averaged from ten steps in the forefoot (primary outcome) and total foot was analysed. Insole comfort was measured with the Insole Comfort Index (ICI, sum score 0–100) after each running trial. The primary outcome was tested using the Friedman test (α = 0.05). Secondary outcomes were analysed descriptively (mean ± SD, lower & upper 95%-CI, median and interquartile-range (IQR)). Results Peak pressure [kPa] in the forefoot was significantly lower wearing FC (281 ± 80, 95%-CI: 246–315) compared to both C (313 ± 69, 95%-CI: 283–343; p = .003) and MP (315 ± 80, 95%-CI: 280–350; p = .001). No significant difference was found between C and MP (p = .858). Peak pressures under the total foot were: C: 364 ± 82, 95%-CI: 328–399; MP: 357 ± 80, 95%-CI: 326–387; FC: 333 ± 81 95%-CI: 298–368. Median ICI sum scores were: C 50, MP 49, FC 64. Conclusions In contrast to the metatarsal pad orthosis, the forefoot cushioning orthosis achieved a significant reduction of peak pressure in the forefoot of recreational runners. Consequently, the use of a prefabricated forefoot cushioning orthosis should be favoured over a prefabricated orthosis with an incorporated metatarsal pad in recreational runners with normal height arches

Mapping the Navigational Information Content of Insect Habitats

For developing and validating models of insect navigation it is essential to identify the visual input insects experience in their natural habitats. Here we report on the development of methods to reconstruct what insects see when making navigational decisions and critically assess the current limitations of such methods. We used a laser-range finder as well as camera-based methods to capture the 3D structure and the appearance of outdoor environments. Both approaches produce coloured point clouds that allow within the model scale the reconstruction of views at defined positions and orientations. For instance, we filmed bees and wasps with a high-speed stereo camera system to estimate their 3D flight paths and gaze direction. The high-speed system is registered with a 3D model of the same environment, such that panoramic images can be rendered along the insects’ flight paths (see accompanying abstract “Benchmark 3D-models of natural navigation environments @ www.InsectVision.org” by Mair et al.). The laser-range finder (see figure A) is equipped with a rotating camera that provides colour information for the measured 3D points. This system is robust and easy-to-use in the field generating high resolution data (about 50 × 106 points) with large field of view, up to a distance of 80 m at typical acquisition times of about 8 minutes. However, a large number of scans at different locations has to be recorded and registered to account for occlusions. In comparison, data acquisition in camera-based reconstruction from multiple view-points is fast, but model generation is computationally more complex due to bundle adjustment and dense pair-wise stereo computation (see figure B, C for views rendered from a 3D model based on 6 image pairs). In addition it is non-trivial and often time-consuming in the field to ensure the acquisition of sufficient information. We are currently developing the tools that will allow us to combine the results of laser-scanner and camera-based 3D reconstruction methods

Einführung

Anlaß, Ziele und Verlauf der Tagung „Psychiatrie in Binswangers Klinik Bellevue. Diagnostik, Therapie, Arzt-Patient-Beziehung“, werden hier einleitend erläutert

Sclerotherapy and prolotherapy for chronic patellar tendinopathies - a promising therapy with limited available evidence, a systematic review

Chronic Patellar tendinopathy (CPT) is a frequent overuse disorder in athletes and active people. Sclerotherapy (ST) and prolotherapy (PT) are, among a wide range of conservative treatment options, two promising therapies and have shown positive results in other tendinopathies. Since the treatments' efficacy and safety are still not defined, this review sought to answer questions on recommendations for use in clinical utility, safety, and how to perform the injection in the most effective way. An electronic database search was conducted following the PRISMA guidelines. Inclusion criteria were set up according to the PICOS-scheme. Included were athletes and non-athletes of all ages with diagnosed painful CPT. Studies including patients suffering from patellar tendinopathy which can be originated to any systemic condition affecting the musculoskeletal system (e.g. disorders associated with rheumatism) and animal studies were excluded. Methodological quality (modified Coleman Methodology Score) and risk of bias (Cochrane Risk of Bias Assessment Tool 2.0) were assessed by two independent reviewers, with disagreements resolved with a third reviewer. The search yielded a total of 416 entries. After screening titles, abstracts, and full texts, ten articles were found for qualitative analysis. The mean Coleman Score was 64.57. Three randomized-controlled trials showed positive results with an increase in VISA-P score or a decrease in VAS or NPPS, respectively. The non-randomized studies confirmed the positive results as well. Among all ten studies no serious adverse events were reported. Based on this limited set of studies, there seems to be some evidence that ST and PT may be effective treatment options to treat pain and to improve function in patients with CPT. To strengthen this recommendation, more research is needed with larger volume studies and randomized controlled studies with long term follow up. LEVEL OF EVIDENCE: IV

Untersuchungen zur Wahrnehmung von Oberflächen- und Beleuchtungsfarben- Chromatische Szenenstatistiken und temporale Integration -

Diese Arbeit aus dem Bereich der Farbkonstanz untersucht mit psychophysikalischen Methoden die zeitliche Integration visueller Information, welche einen Beitrag zur Beleuchtungsschätzung liefern könnte. Dabei stehen die Nutzung chromatischer Regelmäßigkeiten – beschreibbar durch chromatische Szenenstatistiken – im zeitlichen Integrationskontext sowie die Eigenschaften des zeitlichen Informationsintegrationsprozesses im Fokus. Die hier durchgeführten Experimente weisen darauf hin, dass das visuelle System die beiden untersuchten chromatischen Szenenstatistiken – den chromatischen Mittelwert und die Luminanz-Rötlichkeits-Korrelation (LRK) – als Hinweisreize nutzt. Jedoch zeigt sich für die LRK, dass ihre Nutzung von ihrer Ausprägung beeinflusst zu sein scheint. Des Weiteren weisen die Untersuchungen dieser Arbeit darauf hin, dass das visuelle System bei starken Veränderungen der Beobachtungsbedingungen in der Lage ist, den Prozess der zeitlichen Informationsintegration flexibel zu steuern und an die veränderte Situation aktiv anzupassen. Im Rahmen einer dritten Fragestellung wurde die Rolle chromatischer Regularitäten bei der räumlichen Informationsintegration mit dem Ziel untersucht, anhand von Urteilen über Beleuchtungswechsel einen alternativen methodischen Untersuchungszugang zu nutzen, der die Wirkung der Beleuchtungsveränderung direkt erfasst. Hierzu wurde aus der Literatur ein Paradigma übernommen und erweitert. Die durchgeführten Untersuchungen legen den Schluss nahe, dass die Untersuchungsmethode hier ungeeignet ist, denn die Ergebnisse weisen darauf hin, dass bei dieser Erhebung von direkten Urteilen über einen Beleuchtungswechsel, Wahrnehmungsprozesse nicht isoliert von kognitiv überlagernden Vorstellungen von Beleuchtungswechseln erfasst werden konnten