In recent decades, great progress has been made in the contactless detection of infant and child respiratory motion. Systematic camera errors and disturbing environmental influences can have a strong impact on the signal quality of depth cameras. The prevalence of respiratory diseases in children and the central role that respiratory activity plays in the treatment of these conditions necessitate a robust and non-intrusive way of quantifying nocturnal respiratory activity in children. The aim of our study was to assess the robustness of various depth cameras (Microsoft Kinect V2, PMD CamBoard pico flexx, PMD CamBoard pico monstar, ORBBEC Astra Pro, Intel RealSense D435) regarding ambient factors typically found during the use in clinical and home settings. We investigated the influence of viewing angles, reflectivity and IR light on the signal quality. By correlating depth images with respiratory - belt signals, our analyses show that three cameras achieved adequate performance and might be considered for use in contactless assessment of infant or child respiration. Several cameras failed under some of the ambient conditions which are likely to be encountered in real life settings. Therefore, a careful camera selection regarding environmental influences is pivotal.

Because of their resilience, Time-of-Flight (ToF) cameras are now essential components in scientific and industrial settings. This paper outlines the essential factors for modeling 3D ToF cameras, with specific emphasis on analyzing the phenomenon known as “wiggling”. Through our investigation, we demonstrate that wiggling not only causes systematic errors in distance measurements, but also introduces periodic fluctuations in statistical measurement uncertainty, which compounds the dependence on the signal-to-noise ratio (SNR). Armed with this knowledge, we developed a new 3D camera model, which we then made computationally tractable. To illustrate and evaluate the model, we compared measurement data with simulated data of the same scene. This allowed us to individually demonstrate various effects on the signal-to-noise ratio, reflectivity, and distance.

Background: Pediatric respiratory disorders frequently necessitate clinical evaluation, often during sleep. Traditional polysomnography (PSG), while the gold standard for sleep-related respiratory assessment, is resource-intensive and can cause discomfort, particularly in children. Therefore, in a prior published study, we designed and technically validated a video-based prototype for contactless monitoring of respiratory movements. Objective: Our present study aimed to clinically validate the contactless monitoring prototype in pediatric patients, with a primary focus on detecting respiratory rate and identifying abnormal breathing patterns. Methods: Twenty-seven pediatric patients (aged 6 months to 12 years) were recruited from a pediatric sleep laboratory. To monitor thoracoabdominal movements in real time, the prototype employed a time-of-flight camera and a 3D imaging module, coupled with artificial-intelligence-based determination of the region of interest (ROI). Respiratory rates obtained from the prototype were compared to simultaneously recorded PSG data. Data were collected under various conditions, including different sleeping positions. A total of 296 h of respiratory data were acquired, of which selected 60 s segments (54 during N3 sleep and 27 during REM sleep) were analyzed using the prototype and compared with PSG-derived respiratory parameters. Conclusion: The contactless prototype demonstrates that reliable and non-invasive respiratory monitoring is feasible in pediatric patients. It enables accurate detection of respiratory rate as well as abnormal breathing patterns under routine clinical conditions, while reducing patient burden compared with conventional approaches. Its usability and minimal patient discomfort suggest potential for broader clinical adoption. Future work should focus on full-night recordings across all sleep stages and the development of automated data analysis pipelines to facilitate routine clinical implementation.

For electric propulsion (EP) systems, measurement of plume ion currents and densities is a core diagnostic tool. The state of the art, Faraday-Cups (FCs), terminate the beam, since the ions must impinge on a collector plate. Chief among the issues associated with this approach are the emission of secondary electrons, the unknown transmission function of the screening grid used, and backscattering, thus requiring calibration. Direct-Current Current Transformers (DCCT) provide, in principle, an absolute and contactless option for inductively measuring any direct current. For application in typical EP systems, the concept needs to be adapted for small currents $$<{1}\ {\upmu }\text{A}$$ < 1 μ A compared to the established use case in particle accelerators ( $$\gg {1}\ {\upmu }\text{A}$$ ≫ 1 μ A ). A modular prototype was developed and investigated for possible optimizations as well as error sources. The system was tested in the far field of the ion beam of a gridded ion source. However, the measurement does not align with the theoretically expected value. Susceptibility to electromagnetic interference (EMI) and non-periodic drifts in the measurement signal across various timescales were found to introduce noise. Wire-bound test currents down to $$<{10}\ {\upmu }\text{A}$$ < 10 μ A could be reliably measured. The wire-bound tests show promise for DCCTs to complement FCs as a calibration device and alternative for use cases in which FCs show limitations, i.e. for extended, integral, near field, or combined diagnostics.