@article{FuhrmannMandlShamoninChamonine, author = {Fuhrmann, Thomas and Mandl, Roland and Shamonin (Chamonine), Mikhail}, title = {Analysis of learning improvement on changing lab course from single experiments to projects}, series = {International Journal of Electrical Engineering Education}, volume = {52}, journal = {International Journal of Electrical Engineering Education}, number = {4}, publisher = {SAGE}, doi = {10.1177/0020720915583863}, pages = {287 -- 297}, abstract = {During recent years, there has been a trend to replace traditional lab courses by project-based learning activities. However, there is currently little scientific evidence for educational improvements through such changes. Some years ago, a lab course on electrical measurements in our bachelor Electrical Engineering and Information Technology was modified from single experiments to projects. This change led to a significant increase in the necessary manpower and lab costs. To justify these higher efforts, it is important to investigate if the learning success increased. We carried out the surveys and collected the statistical data from the students who attended this course. In order to see if the students appreciated this lab course and if there was an objective increase of the students' knowledge, these results were evaluated. Evaluation of the grades in the lecture and lab courses shows that the increase of the students' theoretical and practical knowledge is statistically significant.}, language = {en} } @article{Fuhrmann, author = {Fuhrmann, Thomas}, title = {Spherical lens aberration minimization method for short-range free-space light transmission}, series = {Optical Engineering}, volume = {61}, journal = {Optical Engineering}, number = {8}, publisher = {SPIE}, address = {Bellingham, Wash.}, issn = {1560-2303}, doi = {10.1117/1.OE.61.8.085101}, abstract = {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.}, language = {en} }