Wavefront predictions for the automated assembly of optical systems

Industrial assembly of optical systems is still a tedious and cost-intensive task that is mostly dominated by manual labor. Positional fine-adjustment of optical components is pivotal to ensure a desired performance of the optical device at hand. In this paper, we use wavefront predictions to aim for fully automated assembly procedures. Wavefront measurements along with position identification methods can be utilized to continuously update a simulation model which in turn allows for predictions on future wavefront errors. This enables to take according correction measures during the assembly process if a certain wavefront tolerance specification is not met. In order to demonstrate the efficacy of the proposed approach and methods, a beam expander is sequentially assembled. The setup consists of a laser, two bi-convex lenses, and a Shack-Hartmann wavefront sensor and has to satisfy a certain wavefront tolerance specification after its assembly. © 2018 SPIE

Predictive tolerance bands for the correction-less assembly of optical systems

When assembling optical systems, uncertainties of the positioning system and overall mounting tolerances lead to the deterioration of performance due to resulting misaligned optical components. In this paper, we present a novel methodology for the correction-less assembly of optical systems based on predictive tolerance bands. By running a simulation model in parallel to the assembly process, performance predictions can be made during the assembly that take into account the uncertainties of the positioning system. Typically, optical performance can be assessed by a variety of criteria. In this paper, we utilize the Marechal criterion based on the root mean square (RMS) error as it allows to verify if the optical system is defraction-limited. The extension with Monte Carlo methods enables the prediction of mean values and standard deviations for the chosen metric. This is done for the entire optical system yet to be assembled by integrating uncertainties of the positioning system within the simulation framework. Before assembly, a desired threshold (here the RMS value derived from the Marechal criterion) can be specified which is predicted and monitored throughout the assembly process. For verification, we analyze a two-lens system in simulation to demonstrate our proposed framework

8. DACH-Studierendentagung der Skandinavistik

Ebenso wie ihre Vorgängerveranstaltungen zielte auch die diesjährige DACH-Tagung darauf ab, den Austausch zwischen den verschiedenen Instituten und Abteilungen innerhalb der deutschsprachigen Skandinavistik zu fördern.1 Aus diesem Grund und um den Teilnehmenden der Tagung eine möglichst breite Bühne für ihre aktuellen Projekte und Interessen zu bieten, wurde bewusst davon abgesehen, ein allgemeines Tagungsthema vorzuschreiben. Dieses Ziel eines freien Austauschs wurde weitgehend erreicht, auch wenn nicht alle Institute des deutschsprachigen Raums durch Teilnehmende repräsentiert waren; beteiligt waren zehn Vertreter_innen der Universitäten München, Wien und Greifswald. Sie präsentierten Ansätze aus so verschiedenen Fachbereichen wie Kulturwissenschaft, Literaturwissenschaft, Digital Philology, Gender Studies und Religionswissenschaft

Stones in swamps: remains of a mythical past in the Sepik area

Early documents on Middle Sepik cultures mention special mounds, which fascinated the first travellers in that region, in front of the huge men’s houses. Situated in the midst of the well-groomed meadows of the so-called dancing grounds, these mounds attracted the explorer’s attention, but their meaning remained hidden. Their beauty was enhanced by tall palm trees and colourful bushes, as well as by carvings – some of them huge – and several upright stones (menhirs, stelae) surrounding the mounds. Later research revealed that they were associated with warfare and headhunting, but also with the founding ancestors of villages. This article summarizes these early descriptions and then proceeds to the later, more detailed research. Additional information is included from the author’s own fieldwork among the Sawos and Kwanga people, and a comparison is made with data from neighbouring cultures of the Middle Sepik region.Les documents anciens sur les cultures du Moyen Sepik mentionnent des buttes remarquables devant les grandes maisons des hommes. Ces buttes fascinèrent les premiers voyageurs dans cette région. Implantées au milieu de l’espace le plus souvent plat fréquemment qualifié de place de danse, elles attirèrent l’attention mais sans révéler leur sens. Leur beauté était soulignée par des bouquets de palmiers et des plantes au feuillage coloré qui entouraient la butte et auxquels étaient parfois mêlées de grandes sculptures. Quelques fois, elles étaient entourées de plusieurs pierres dressées, menhirs ou stèles. Des recherches plus récentes ont montré que ces buttes devaient être mises en relation avec la guerre et la chasse aux têtes mais aussi avec les ancêtres fondateurs du village. L’article résume les premières descriptions et rend compte des recherches détaillées plus récentes. Des informations complémentaires provenant de mes recherches de terrain chez les Sawos et les Kwanga sont données et une comparaison est faite avec les informations sur les cultures voisines du moyen Sepik