Abstract
Extreme Learning Machines (ELMs) are a versatile Machine Learning (ML) algorithm that features as the main advantage the possibility of a seamless implementation with physical systems. Yet, despite the success of the physical implementations of ELMs, there is still a lack of fundamental understanding in regard to their optical implementations. In this context, this work makes use of an optical complex media and wavefront shaping techniques to implement a versatile optical ELM playground to gain a deeper insight into these machines. In particular, we present experimental evidences on the correlation between the effective dimensionality of the hidden space and its generalization capability, thus bringing the inner workings of optical ELMs under a new light and opening paths toward future technological implementations of similar principles.

Abstract
A comparative analysis on the performance of different scanning regimes in time domain optical coherence tomography is presented in terms of image size. Safety thresholds due to the different continuous irradiation time per transverse pixel in different scanning regimes are also considered. We present the maximum exposure level for a variety of scanning procedures, employing either A scanning (depth priority) or T scanning (transverse priority) when generating cross section images, en face images or collecting 3D volumes. We present a comparison between such B-scan images, and different criteria to allow the user to choose the right mode of operation. Mainly, two criteria are detailed, a scanning criterion and a safety criterion. The scanning criterion depends on the number of pixels along the lateral and axial directions. The analysis shows that en-face scanning allows wider images while the longitudinal scanning is more suitable to deep cross sections. The safety criterion refers to safety levels to be observed in each scanning mode. We show that the flying spot OCT imaging has different safety limits for T- and A- based imaging modes. The analysis leads to maximum permissible optical power levels that favors T-scan imaging of wide objects. We then apply the analysis considering as object the eye.

Abstract
A new transmissive grating-based scanning delay-line for optical coherence tomography is proposed, with dispersion compensation capability. Compared to other spectral delay-lines, our implementation has less loss due to a halved number of diffraction grating reflections, and implements a walk off compensation scheme. The performance of the delay line is evaluated. The delay line transmissive geometry targets balance detection configurations. © 2005 SPIE and OSA.

Abstract
A novel Fourier domain fast scanning optical delay line is proposed in which the walk-off is eliminated by only two passes through a diffraction grating. Working in transmission, the novel delay line is ideal for balanced optical coherence tomography configurations with recirculation of the reference beam. We evaluate theoretically and experimentally its walk-off and dispersion compensation capabilities. (c) 2005 Optical Society of America

Abstract
We present the time variant second order statistics of the depth-scan photocurrent in timedomain optical coherence tomography (TD-OCT) systems using polarized thermal light sources. Our results are prerequisite for future development of statistical image processing techniques for TD-OCT. © 2007 Optical Society of America.

Abstract
The European Space Research and Technology Center ESTEC, ESA's premises in Noordwijk, The Netherlands, has a long lasting cooperation with the ZARM-FAB (Centre of Applied Space Technology and Microgravity-Drop Tower Operation and Service Company) in Bremen on the utilization of the Drop Tower for ground-based microgravity research and space hardware development studies. During the period January 2000 to December 2011 ESA will have procured in total some 840 drops addressing a variety of scientific and technological disciplines. The experiments are usually carried out in campaigns of 15 to 20 drops each, with an annual average of about 5 campaigns. The cooperation agreement between ESA and the ZARM-FAB includes experiment preparation advice by ZARM's experts, the integration of the hardware into the drop capsule, dedicated safety reviews, the execution of the drop or catapult experiments, the post-flight payload de-integration as well as the handover of acquired data to the experimenters. The experiment hardware itself is provided by the scientists or has to be procured from sources outside of ESA's drop tower utilization contract. ESA appreciates the cooperation of the ZARM-FAB in Bremen whose drop-and catapult facility provides excellent microgravity quality, is operated by a highly competent, flexible and extremely supportive expert team, allows campaign integration at relatively short notice throughout the entire year, offers real-time experiment operations and immediately after each drop delivers experiment results and provides on-site hardware modification possibilities.