TY - JOUR A1 - Fuhrmann, Thomas T1 - Spherical lens aberration minimization method for short-range free-space light transmission JF - Optical Engineering N2 - Spherical aberrations of lenses lead to increased spot radii on the focal plane. Several methods, such as optimizing thickness and radii or building lens groups, are known to minimize these spherical aberrations. Here, an innovative method for spherical aberration minimization is introduced; it can be used for short-range free-space optical communication systems, such as unit power afocal relay trains, lens waveguides, and periodic lens systems. This spherical aberration compensation principle is based on the combination of two identical spherical convex lenses at an optimal distance. Due to the higher refractive power for rays with an larger axis distance, rays from the outer area of the first lens intersect the inner area of the second lens, and vice versa. With this setup, the radial refractive power deviation of the two lenses compensate each other. Analytic calculations and numerical simulations are done to confirm this behavior, and measurements using two symmetric spherical lenses with polymer optical fibers as light feed confirm the calculations. Simulations and measurements show a very good matching behavior except for an unknown systematic error. At a lens distance of 300 mm, the optical attenuation decreased by ∼2 dB compared with a very small lens distance. This leads to the conclusion that this proposed spherical aberration minimization method works as theoretically predicted. KW - Monochromatic aberrations KW - Signal attenuation KW - Spherical lenses KW - Polymer optical fibers KW - Monte Carlo methods KW - Free space optics KW - Optical testing KW - Distance measurement KW - Optical engineering KW - Optical simulations Y1 - 2022 U6 - https://doi.org/10.1117/1.OE.61.8.085101 SN - 1560-2303 SN - 0036-1860 SN - 0091-3286 VL - 61 IS - 8 PB - SPIE CY - Bellingham, Wash. ER - TY - CHAP A1 - Fuhrmann, Thomas T1 - Course Preparation Time Optimization System for Improved Didactic Outcome T2 - 2022 20th International Conference on Information Technology Based Higher Education and Training (ITHET), 07-09 November 2022, Antalya, Turkey N2 - Due to the various demands for lecturers, there is only a limited time to prepare lectures and lab courses. Therefore, it is necessary to invest the time target-oriented for optimal student learning success. A theoretic model is developed to structure course preparation work regarding scientific content, didactic preparation, and course presentation. Model parameters have to be chosen for each course depending on topic complexity, the lecturer’s prior knowledge, and the already available preparation from the prior semesters. With these parameters, a course preparation model for a complete semester is developed. Analytic models for different optimization strategies are introduced according to the overall goal of the lecturer. Numerical optimization is done to find the appropriate course preparation times to reach an optimal course preparation for high student learning success. It is seen that due to the different optimization strategies, the preparation time results vary and no single truth is given. But this optimization system gives hints on how to invest preparation time target-oriented for high student learning success. KW - Higher education KW - Engineering education KW - Course preparation KW - Curriculum development KW - Optimization Y1 - 2022 SN - 978-1-6654-8908-9 U6 - https://doi.org/10.1109/ITHET56107.2022.10031642 PB - IEEE ER -