Fraunhofer-Institut für Optronik, Systemtechnik und Bildauswertung IOSB

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  • Publication
    Comparative analysis of C²ₙ estimation methods for sonic anemometer data
    ( 2024-06-01)
    Beason, M.
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    Potvin, G.
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    Sprung, Detlev
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    McCrae, J.
    ;
    Gladysz, Szymon
    Wind speed and sonic temperature measured with ultrasonic anemometers are often utilized to estimate the refractive index structure parameter C²ₙ, a vital parameter for optical propagation. In this work, we compare four methods to estimate C²ₙ from CT2 , using the same temporal sonic temperature data streams for two separated sonic anemometers on a homogenous path. Values of C²ₙ obtained with these four methods using field trial data are compared to those from a commercial scintillometer and from the differential image motion method using a grid of light sources positioned at the end of a common path. In addition to the comparison between the methods, we also consider appropriate error bars for C²ₙ based on sonic temperature considering only the errors from having a finite number of turbulent samples. The Bayesian and power spectral methods were found to give adequate estimates for strong turbulence levels but consistently overestimated the C²ₙ for weak turbulence. The nearest neighbors and structure function methods performed well under all turbulence strengths tested.
  • Publication
    Optimization of the slope efficiency of a core-pumped thulium-doped fiber laser by the thermally diffused expanded-core technique
    ( 2024-05-15)
    Panitzek, Dieter
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    Romano, Clément
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    Eichhorn, Marc
    ;
    Kieleck, Christelle
    We report on the mode field adaption of an active thulium-doped fiber by using the thermally-diffused expanded-core technique. The fiber core diffusion is analyzed by splice transmission measurements and visually from side view images. The obtained heating parameters are used to build a thulium-doped fiber laser emitting at 2036nm that is core-pumped by an erbium:ytterbium fiber laser. By allowing the fiber cores to diffuse, the mode fields of the active and passive fibers are adapted for both the signal and pump wavelength. The adaptation of the mode fields increases the slope efficiency from 66.1% to 75.0%. The obtained slope efficiency is close to the stoke efficiency of 77.0%. By comparing the results with a fiber laser simulation, the slope efficiency of 75.0% is verified to be the maximum slope efficiency taking the active fiber length into account.
  • Publication
    Simulation of the reflection of a high energy laser beam at the sea surface for hazard and risk analyses
    ( 2024-04-10)
    Schwenger, Frederic
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    Azarian, Adrian
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    Henrichsen, Michael
    The application of a high energy laser beam in a maritime scenario necessitates a laser safety concept to prevent injury to personnel or uninvolved third parties from uncontrolled reflections of laser light from the sea surface. Therefore, it is crucial to have knowledge of the amount and direction of reflected laser energy, which varies statistically and depends largely on the dynamics of the wavy sea surface. These dynamics are primarily influenced by wind speed, wind direction, and fetch. An analytical model is presented for calculating the time-averaged spatial intensity distribution of the laser beam reflected at the dynamic sea surface. The model also identifies the hazard areas inside which laser intensities exceed a fixed exposure limit. Furthermore, as far as we know, our model is unique in its ability to calculate the probabilities of potentially eye-damaging glints for arbitrary observer positions, taking into account the slope statistics of gravity waves. This is a critical first step toward an extensive risk analysis. The simulation results are presented on a hemisphere of observer positions with fixed radii from the laser spot center. The advantage of the analytical model over our numeric (dynamic) model is its fast computation time. A comparison of the results of our new analytical model with those of the previous numerical model is presented.
  • Patent
    Network node for a non-detectable laser communication system
    ( 2024-02-07)
    Kieleck, Christelle
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    Eichhorn, Marc
    ;
    Rudow, Oliver
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    Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
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    Hensoldt Sensors GmbH
    A network node (120) for a non-detectable laser communication system (100), wherein the laser communication system (100) is configured to send to the network node (120) at least one laser beam (10), comprises a reflector device (123), configured to generate, by a reflection of the laser beam (10), a reflected laser beam (20), and a modulator device (125), configured to provide a modulation of the reflected laser beam (20).
  • Publication
  • Publication
    A survey of the state of the art in sensor-based sorting technology and research
    ( 2024)
    Maier, Georg
    ;
    Gruna, Robin
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    Längle, Thomas
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    Beyerer, Jürgen
    Sensor-based sorting describes a family of systems that enable the removal of individual objects from a material stream. The technology is widely used in various industries such as agriculture, food, mining, and recycling. Examples of sorting tasks include the removal of fungus-infested grains, the enrichment of copper content in copper mining or the sorting of plastic waste according to the type of plastic. Sorting decisions are made based on information acquired by one or more sensors. A particular strength of the technology is the flexibility in sorting decisions, which is achieved by using various sensors and programming the data analysis. However, a comprehensive understanding of the process is necessary for the development of new sorting systems that can address previously unresolved tasks. This survey is aimed at innovative researchers and practitioners who are unfamiliar with sensor-based sorting or have only encountered certain aspects of the overall process. The references provided serve as starting points for further exploration of specific topics.
  • Publication
    Utilizing Dataset Affinity Prediction in Object Detection to Assess Training Data
    ( 2024)
    Becker, Stefan
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    Bayer, Jens
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    Hug, Ronny
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    Hübner, Wolfgang
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    Arens, Michael
    Data pooling offers various advantages, such as increasing the sample size, improving generalization, reducing sampling bias, and addressing data sparsity and quality, but it is not straightforward and may even be counterproductive. Assessing the effectiveness of pooling datasets in a principled manner is challenging due to the difficulty in estimating the overall information content of individual datasets. Towards this end, we propose incorporating a data source prediction module into standard object detection pipelines. The module runs with minimal overhead during inference time, providing additional information about the data source assigned to individual detections. We show the benefits of the so-called dataset affinity score by automatically selecting samples from a heterogeneous pool of vehicle datasets. The results show that object detectors can be trained on a significantly sparser set of training samples without losing detection accuracy. T
  • Publication
    Quantum computer-aided job scheduling for storage and retrieval systems
    ( 2024)
    Windmann, Stefan
    In this paper, a quantum computer-aided approach to job scheduling for automated storage and retrieval systems is introduced. The approach covers application cases, where various objects need to be transported between storage positions and the order of transport operations can be freely chosen. The objective of job scheduling is to arrange the transport operations in a sequence, where the cumulative costs of the transport operations and empty runs between subsequent transport operations are minimized. The scheduling problem is formulated as an asymmetric quadratic unconstrained binary optimization (QUBO) problem, in which the transport operations are modeled as nodes and empty runs are modeled as edges, with costs assigned to each node and each edge. An Quantum Approximate Optimization Algorithm (QAOA) is used to solve the QUBO. Evaluations of the quantum computer-aided job scheduling approach have been conducted on the IBM Q System One quantum computer in Ehningen. In particular, the running time for the solution of the QUBO has been investigated, as well as the scalability of the approach with respect to the required number of qubits.
  • Publication
    Enhancing Skeleton-Based Action Recognition in Real-World Scenarios Through Realistic Data Augmentation
    ( 2024)
    Cormier, Mickael
    ;
    Schmid, Yannik
    ;
    Beyerer, Jürgen
    Skeleton-based action recognition is a prominent research area that provides a concise representation of human motion. However, real-world scenarios pose challenges to the reliability of human pose estimation, which is fundamental to such recognition. The existing literature mainly focuses on laboratory experiments with near-perfect skeletons, and fails to address the complexities of the real world. To address this, we propose simple yet highly effective data augmentation techniques based on the observation of erroneous human pose estimation, which enhance state-of-the-art methods for real-world skeleton-based action recognition. These techniques yield significant improvements (up to +4.63 accuracy) on the widely used UAV Human Dataset, a benchmark for evaluating real-world action recognition. Experimental results demonstrate the effectiveness of our augmentation techniques in compensating for erroneous and noisy pose estimation, leading to significant improvements in action recognition accuracy. By bridging the gap between laboratory experiments and real-world scenarios, our work paves the way for more reliable and practical skeleton-based action recognition systems. To facilitate reproducibility and further development, the Skelbumentations library is released at https://github.com/MickaelCormier/Skelbumentations. This library provides the code implementation of our augmentation techniques, enabling researchers and practitioners to easily augment skeleton sequences and improve the performance of skeleton-based action recognition models in real-world applications.
  • Publication
    Tiled aperture coherent beam combination of 2 μm fiber lasers
    ( 2024)
    Romano, Clément
    ;
    Panitzek, Dieter
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    Pradat-Peyre, Gabriel
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    Milcent, Simon
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    Uthayakumar, Jashaani
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    Eichhorn, Marc
    ;
    Kieleck, Christelle
    Exceeding the multi-kW power level with thulium-doped fiber lasers has not been achieved using a single thulium-doped fiber laser. One solution to overcome this limit is the coherent beam combination. We focus on an active phase control with tiled aperture configuration. The setup consists in an amplified seed laser split in three channels. These channels are controlled in phase and amplified again before being launched free space and combined. A SPGD algorithm controls the channel’s phase to provide combination. Rise time below 0.5 ms were achieved with a residual amplitude noise lower than λ/30.