Investigation on chromatic aberrations and its potential for application in depth measurement. - In: Measurement: sensors. - [London] : Elsevier Ltd., ISSN 2665-9174, Bd. 18 (2021), S. 1-4
Chromatic aberrations are mostly supressed in typical industrial lenses to ensure a well-defined colour image. Beside the main wavelengths which are recognizable for the human eye, multispectral cameras can sample with a more detailed chromatic (spectral) resolution. This leads to a partial wavelength depended unsharpness in the images. If the imaging system can be well defined out of these imperfections, a depth information can be calculated. In this paper the theoretical model as well as a method for the 3D-reconstruction out of different colour (spectral) channels will be discussed.
Real-time multimodal 3D imaging system for remote estimation of vital signs. - In: Multimodal Sensing and Artificial Intelligence: Technologies and Applications II : 21-25 June 2021, online only, Germany.. - Bellingham, Washington, USA : SPIE, (2021), S. 117850F-1-117850F-14
The contactless estimation of vital signs based on conventional color cameras and ambient light can be affected by motions of patients and changes in ambient light. In this work, a multimodal 3D imaging system with an irritation-free controlled illumination was developed in order to mitigate these both problems. In the developed system the real-time high-precision 3D imaging is combined with VIS-NIR multispectral imaging and thermal imaging. Based on 3D data and color images, an approach was proposed for the efficient compensation of head motions, and novel approaches based on 3D regions of interest were developed for the estimation of heart rate, oxygen saturation, respiration rate, and body temperature from NIR multispectral video data and thermal video data. A proof-of-concept for the developed imaging system and algorithms can be delivered with first experimental results.
Measurement accuracy and practical assessment of the lidar camera Intel RealSense L515. - In: Optical Measurement Systems for Industrial Inspection XII : 21-25 June 2021, online only, Germany.. - Bellingham, Washington, USA : SPIE, (2021), S. 1178213-1-1178213-12
LiDAR technology is increasingly being used as an area-based 3D measurement method. In addition to high aspirations in terms of accuracy, speed and resolution, manufacturers of lidar cameras are competing to reduce size, weight and power consumption. As one of the most compact high-resolution systems, the Intel RealSense L515 has undergone extensive testing according to VDI/VDE Guideline 2634. In addition, tests were conducted with glossy or partially transparent surfaces (acrylic glass, carbon fiber material and aluminum) as well as with human skin. The latter shows the applicability for human-machine interactions. Both laboratory conditions and the influence of natural light were used as environmental conditions. A comparison of the results is given by the Intel RealSense D415 stereo camera system.
Irritation-free optical 3D-based measurement of tidal volume. - In: Automated Visual Inspection and Machine Vision IV : 21-25 June 2021, online only, Germany.. - Bellingham, Washington, USA : SPIE, (2021), S. 117870A-1-117870A-7
The measurement of breathing biomechanics, such as tidal volume, can be used to assess both the breathing performance and the respiratory health of individuals. State-of-the-art methods like spirometry or body plethysmography require a mouthpiece or facemask., which can be uncomfortable to the test person. As an alternative, we propose to use the change of the geometric shape of the subjects torso while breathing. By acquiring 3D point clouds of the person with a real-time near-infrared (NIR) 3D scanner, we measure those changes in a comfortable, irritation-free, and contact-free manner. Accordingly, two continuously measuring structured light 3D sensors, using a GOBO-based aperiodic sinusoidal pattern projector at a wavelength of 850 nm, simultaneously capture the upper front and side torso of the subject at a frame rate of 200 Hz. Both 3D scanners are calibrated and operated in a sensor network fashion, yielding a unified data stream within a global coordinate system. This results in increased coverage and reduced occlusion of the patient's body shape, enabling robust measurements even in the presence of loose clothing and varying body figure. We collected data from 16 healthy participants in an upright sitting position, wearing everyday clothing during the measurements. For reference, we simultaneously recorded spirometry readings. An algorithm ("OpTidal") tracks the volume of the subject's torso from the 3D data. Comparison whith the reference data shows high correlation and low mean error for the absolute tidal volume readings. As such, our method is a viable, safe, and accurate alternative to spirometry and plethysmography.
Kl-gesteuerte Prozesskontrolle für das Selektive Laserschmelzen. - In: Innovative Verfahren der Lasermaterialbearbeitung. - Düsseldorf : DVS Media GmbH, (2021), S. 142-151
Echtzeitfähige Ansätze zum Monitoring der dehnungsfeldbasierten Spaltentstehung und resultierender Nahtqualität beim Laserstrahlschweißen. - In: Innovative Verfahren der Lasermaterialbearbeitung. - Düsseldorf : DVS Media GmbH, (2021), S. 44-55
High-resolution sequential thermal fringe projection technique for fast and accurate 3D shape measurement of transparent objects. - In: Applied optics. - Washington, DC : Optical Soc. of America, ISSN 2155-3165, Bd. 60 (2021), 8, S. 2362-2371
Three-dimensional (3D) shape measurement systems based on diffuse reflection of projected structured light do not deliver reliable data when measuring glossy, transparent, absorbent, or translucent objects. In recent years, we have developed a method based on stereo recording with infrared cameras and projection of areal aperiodic sinusoidal thermal patterns to detect such objects. However, the measurements took longer than 10 s, up to minutes; moreover, the measurement accuracy was improvable. Now, we have succeeded in both drastically reducing measurement time and significantly increasing measurement quality. This finally provides a technique for reliably measuring transparent objects, e.g., in series production. We demonstrate measurement examples achieved within 1 s and with 3D standard deviations less than 10 [my]m.
Imaging flow cytometry with snapshot-mosaic cameras for characterization of Haematococcus pluvialis cells. - In: Microfluidics, BioMEMS, and Medical Microsystems XIX : 6-11 March 2021, online only, United States.. - Bellingham, Washington, USA : SPIE, (2021), S. 116370R-1-116370R-7
The evaluation of CUDA performance on the Jetson Nano board for an image binarization task. - In: Real-Time Image Processing and Deep Learning 2021 : 12-16 April 2021, online only, United States.. - Bellingham, Washington, USA : SPIE, (2021), S. 117360G-1-117360G-8
One of the most preferred platforms or boards for developing 'real-time image-video processing' applications is NVIDIA's Jetson Nano, which is equipped with CUDA that will accelerate the performance. However, there is no research has yet evaluated CUDA performance on the Jetson Nano for Real-Time Image/Video Processing applications. Through this research, an evaluation of the CUDA performance on Jetson Nano will be obtained by running the Thresholding application with and without the CUDA feature. Some of the aspects evaluated from this study are as follows: CPU usage percentage, GPU usage percentage, temperature level, Current Usage on CPU, Current Usage on GPU from the research results, it was found that the CUDA feature does not always provide added value or performance in its use, CUDA will run very effectively when offline (not real-time), but in real-time, the performance with and without CUDA is almost the same.
Mid-wave infrared 3D sensor based on sequential thermal fringe projection for fast and accurate shape measurement of transparent objects. - In: Dimensional Optical Metrology and Inspection for Practical Applications X : 12-16 April 2021, online only, United States.. - Bellingham, Washington, USA : SPIE, (2021), S. 1173204-1-1173204-11
Structured light sensors based on diffuse reflection of projected patterns are widely used to measure the 3D shape of objects, e.g., in industry, medicine, or cultural heritage. Unfortunately, there exist many objects made of uncooperative materials, i.e., materials with optical properties such as being glossy, transparent, absorbent, or translucent, which cannot be measured reliably by this measurement technique. In the last years, we presented a two-step method based on thermal pattern projection which allows the determination of the object surface of these uncooperative objects. In the first step, a multi-fringe thermal pattern is projected onto the measurement object. In the second step, a mid-wave infrared (MWIR) stereo camera records the thermal radiation that is absorbed and re-emitted by the object surface. This system allows us to measure transparent objects. However, the measurement time is with tens of seconds up to minutes quite long and the measurement accuracy should be improved. In this contribution, we present a projection principle of a fast sequentially scanning fringe leading to a significant reduction in measurement periods down to the second range or even below while increasing the measurement accuracy. The work includes a characterization of our MWIR 3D setup for both projection principles, the multifringe and sequential fringe one, regarding the measurement accuracy and speed. We show measurement results obtainted with both projection techniques for an object made of different material classes.