Entwurf und Erzeugung neuartiger diffraktiver Optiken durch die Mikrostrukturierung von Kontaktlinsenoberflächen

In dieser Arbeit werden die Möglichkeiten zur Herstellung von diffraktiven optischen Elementen, Fresnelsche Zonenplatten und Photonensieben auf Kontaktlinsenoberflächen zum Ausgleich von Sehfehlern des menschlichen Auges untersucht. Dabei wird beschrieben, inwieweit sich die Elektronenstrahllithographie zur Applikation dieser Optiken auf entsprechende Trägermedien eignet. Da formstabile Kontaktlinsen eine besonders gute und sichere Anwendung am menschlichen Auge ermöglichen, wurden diese als Testmedien verwendet. Ein fundamental neuer Ansatz ist, die von Kipp et al entwickelte Photonensiebtechnologie für die Anwendung als Korrektionssystem nutzbar zu machen. Da sich die Technik bei der Fokussierung von Röntgenstrahlung als optisch überlegen herausgestellt hat, liegt der Gedanke nahe, dass dies auch unter normalen Bedingungen im polychromatischen Tageslicht der Fall ist. Diese Arbeit verbindet die Anwendung von Dünnfilm- und Lithographietechniken mit der Berechnung neuer physikalisch-optischer Zonenplatten- und Photonensiebtechnologie im Zusammenspiel mit physiologisch-optischen Parametern des menschlichen Auges und somit die Gebiete Materialwissenschaft, Physik und Optometrie. Die Anwendung der Elektronenstrahllithographie zur Erzeugung diffraktiver optischer Elemente auf Kontaktlinsen stellt ein Novum dar. In dieser Arbeit wird untersucht, inwieweit sich das Verfahren zur Fertigung individueller Kontaktlinsen eignet. Dazu werden die verschiedenen Anwendungsbereiche definiert und die erforderliche Genauigkeit der optischen Elemente zum Ausgleich menschlicher Sehfehler definiert. Die vorliegende Arbeit gliedert sich in drei große Teile. Im ersten Teil werden die anatomischen und physiologischen Zusammenhänge des komplexen visuellen Systems betrachtet. Der zweite Teil befasst sich mit den physikalisch-optischen Ableitungen von Korrektionsmitteln und fertigungstechnischen Besonderheiten der Elektronenstrahllithographie. Der dritte Teil ist der Kernteil der Arbeit und befasst sich mit Berechnungen diffraktiver optischer Elemente, der experimentellen Fertigung dieser auf flachen Substraten und formstabilen Kontaktlinsen mittels Elektronenstrahllithographie, sowie der Bewertung der optischen Eigenschaften der somit erzeugten optischen Systeme. Zur Berechnung werden realistische Daten und Anforderungen des menschlichen Sehsystems verwendet. Die experimentelle Fertigung diffraktiver optischer Elemente, insbesondere die Schreibfeldgröße, wurde maßgeblich durch die technische Ausstattung zur Durchführung der Elektronenstrahllithographie bestimmt. Daher wurde die Berechnung der Größe und optischen Parameter der applizierten Zonenplatten- und Photonensiebstrukturen diesen Gegebenheiten angepasst. Geeignete Beschichtungsmaterialien wurden in Form von Chrom, für flache Substrate, und Gold, für Kontaktlinsen, angewendet. Einige fertigungstechnische Probleme, wie die Oberflächenaufladung der Kontaktlinsen, mussten überwunden werden. Zur Aufnahme der Kontaktlinsen wurde ein spezieller Probenhalter konstruiert und eingesetzt. Alternativ werden ebenfalls die UV-Lithographie und die Applikation von Lack mittels Tampondruck als Verfahren zur Erzeugung diffraktiver optischer Elemente auf ihre Eignung hin betrachtet. Abgeschlossen wird diese Arbeit mit der Diskussion der Ergebnisse und dem Ausblick für eine Anwendung der Elektronenstrahllithographie zur Herstellung von Muttermasken für die vergleichsweise schnelle und preisgünstige Herstellung von multifokalen formstabilen Kontaktlinsen im Pressschmelzverfahren und Weichlinsen im Cast-Moulding Verfahren, bzw. mit der Light-Stream-Technologie

Automatic Behavior Assessment from Uncontrolled Everyday Audio Recordings by Deep Learning

The manual categorization of behavior from sensory observation data to facilitate further analyses is a very expensive process. To overcome the inherent subjectivity of this process, typically, multiple domain experts are involved, resulting in increased efforts for the labeling. In this work, we investigate whether social behavior and environments can automatically be coded based on uncontrolled everyday audio recordings by applying deep learning. Recordings of daily living were obtained from healthy young and older adults at randomly selected times during the day by using a wearable device, resulting in a dataset of uncontrolled everyday audio recordings. For classification, a transfer learning approach based on a publicly available pretrained neural network and subsequent fine-tuning was implemented. The results suggest that certain aspects of social behavior and environments can be automatically classified. The ambient noise of uncontrolled audio recordings, however, poses a hard challenge for automatic behavior assessment, in particular, when coupled with data sparsity

A questionnaire to estimate the needs for research data management

The development of a data management plan requires detailed knowledge about the research data and the corresponding processes. Moreover, detailed knowledge about the entire data life-cycle in the respective research group is necessary when providing support with respect to reproducibility and data management. In order to allow curators to gain this knowledge, we developed a questionnaire, which provides a set of topics including questions to inspire discussions on data management and the data life-cycle. This questionnaire consists of a collection of questions targeting different phases of the data life-cycle. It was developed in order to gain insight about the data management practices in the subproject of the collaborative research centre 1270 ELAINE, but can also be used as guideline for so interviews with individual research groups

Detection of Constant Phase Shifts in Filters for Sound Field Synthesis

Filters with constant phase shift in conjunction with 3/6 dB amplitude decay per octave frequently occur in sound field synthesis and sound reinforcement applications. These ideal filters, known as (half) differentiators, exhibit zero group delay and 45/90 degree phase shift. It is well known that certain group delay distortions in electro-acoustic systems are audible for trained listeners and critical audio stimuli, such as transient, impulse-like and square wave signals. It is of interest if linear distortion by a constant phase shift is audible as well. For that, we conducted a series of ABX listening tests, diotically presenting non-phase shifted references against their treatments with different phase shifts. The experiments revealed that for the critical square waves, this can be clearly detected, which generally depends on the amount of constant phase. Here, -90 degree (Hilbert transform) is comparably easier to detect than other phase shifts. For castanets, lowpass filtered pink-noise and percussion the detection rate tends to guessing for most listeners, although trained listeners were able to discriminate treatments in the first two cases based on changed pitch, attack and roughness cues. Our results motivate to apply constant phase shift filters to ensure that also the most critical signals are technically reproduced as best as possible. In the paper, we furthermore give analytical expressions for discrete-time infinite impulse response of an arbitrary constant phase shifter and for practical filter design

In-Vivo Evaluation of Peripheral Refraction Changes with Single Vision and Multifocal Soft Contact Lenses

This study investigated in-vivo changes of peripheral refraction with commercially available single vision and multifocal soft contact lenses, utilizing different designs and various corrective power values. Starting at the fovea, wave-front aberrations were measured up to 30o nasal retinal eccentricity, in 10o increments, using a commercially available Shack-Hartmann aberrometer. Three different types of contact lenses were fitted in an adult subject’s right eye: Acuvue Oasys Single Vision (ASV), Proclear Multifocal D with 2.50 diopters (D) add power (PMD), and ArtMost SoftOK (SOK). Each lens type was fitted in corrective power values of -2.00 D, -4.00 D, and -6.00 D. Refractive errors were computed in power vector notation: The spherical equivalent (M), the Cartesian Jackson-Cross-Cylinder (J0), and the oblique Jackson Cross Cylinder (J45) from measured second order Zernike terms. Acuvue Oasys Single Vision lenses produced a slight myopic shift at 30o retinal periphery (-0.32 D ± 0.05) without significant differences between the various lens power values. Proclear Multifocal D lenses did not create clinically significant myopic shifts of at least -0.25 D. All SOK lenses produced clinically significant relative myopic shifts at both 20o (-0.61 D ± 0.08) and 30o (-1.42 D ± 0.15) without significant differences between the various lens power values. For all lens types and power values, off-axis astigmatism J0 was increased peripherally and reached clinical significance beyond 20o retinal eccentricity. The increased amount of off-axis astigmatism J0 did not show a significant difference for the same type of lenses with different dioptric power. However, at 30o retinal eccentricity, SOK lenses produced significantly higher amounts of off-axis astigmatism J0, compared with ASV and PMD lenses (SOK versus ASV versus PMD: -1.67 D ± 0.09, -0.81 D ± 0.07, and -0.72 D ± 0.15). Both ASV and SOK lenses showed no clinically significant differences in the amount of introduced astigmatic retinal image blur, with various lens power values. Proclear Multifocal D lenses showed a systematic increase of astigmatic retinal image blur with an increase of add power. At 30o retinal eccentricity, -6.00 D SOK lenses introduced 0.73 D astigmatic retinal image blur, while PMD and ASV lenses introduced 0.54 D and 0.37 D, respectively. In conclusion, relative peripheral refractions, measured in-vivo, were independent of the contact lenses central corrective power. The SOK contact lenses demonstrated a stronger capability in rendering relative peripheral myopic defocus into far periphery, compared to the other lens designs used in this study. This was accompanied by higher amounts of introduced astigmatic retinal image blur

Optical Rehabilitation of a Patient with Keratoconus and Nystagmus

Keratoconus is a progressive corneal disease characterized by bilateral yet usually asymmetric thinning of the cornea with an onset typically in teenage years.  While it often presents as an isolated condition, keratoconus may also be associated with many systemic and/or ocular diseases, such as connective tissue and chromosomal disorders.  Its association with nystagmus has been described in Leber’s congenital amaurosis, where patients also exhibit abnormal pupillary responses, early-onset retinal dystrophy, mental developmental delays, and eventual blindness.  The case described here, however, was a high-functioning teenager with keratoconus and infantile nystagmus, and oscillopsia on left gaze and a compensatory head turn to the patient’s left. The initial distance visual acuities of 20/60 and 20/150 in the right and left eye, respectively improved to 20/25 and 20/40 by the use of corneal rigid gas permeable contact lenses. In addition, the patient’s neck strain and overall gait were eased by yoked prism spectacles

In-Vivo Evaluation of Peripheral Refraction Changes with Single Vision and Multifocal Soft Contact Lenses

This study investigated in-vivo changes of peripheral refraction with commercially available single vision and multifocal soft contact lenses, utilizing different designs and various corrective power values. Starting at the fovea, wave-front aberrations were measured up to 30o nasal retinal eccentricity, in 10o increments, using a commercially available Shack-Hartmann aberrometer. Three different types of contact lenses were fitted in an adult subject’s right eye: Acuvue Oasys Single Vision (ASV), Proclear Multifocal D with 2.50 diopters (D) add power (PMD), and ArtMost SoftOK (SOK). Each lens type was fitted in corrective power values of -2.00 D, -4.00 D, and -6.00 D. Refractive errors were computed in power vector notation: The spherical equivalent (M), the Cartesian Jackson-Cross-Cylinder (J0), and the oblique Jackson Cross Cylinder (J45) from measured second order Zernike terms. Acuvue Oasys Single Vision lenses produced a slight myopic shift at 30o retinal periphery (-0.32 D ± 0.05) without significant differences between the various lens power values. Proclear Multifocal D lenses did not create clinically significant myopic shifts of at least -0.25 D. All SOK lenses produced clinically significant relative myopic shifts at both 20o (-0.61 D ± 0.08) and 30o (-1.42 D ± 0.15) without significant differences between the various lens power values. For all lens types and power values, off-axis astigmatism J0 was increased peripherally and reached clinical significance beyond 20o retinal eccentricity. The increased amount of off-axis astigmatism J0 did not show a significant difference for the same type of lenses with different dioptric power. However, at 30o retinal eccentricity, SOK lenses produced significantly higher amounts of off-axis astigmatism J0, compared with ASV and PMD lenses (SOK versus ASV versus PMD: -1.67 D ± 0.09, -0.81 D ± 0.07, and -0.72 D ± 0.15). Both ASV and SOK lenses showed no clinically significant differences in the amount of introduced astigmatic retinal image blur, with various lens power values. Proclear Multifocal D lenses showed a systematic increase of astigmatic retinal image blur with an increase of add power. At 30o retinal eccentricity, -6.00 D SOK lenses introduced 0.73 D astigmatic retinal image blur, while PMD and ASV lenses introduced 0.54 D and 0.37 D, respectively. In conclusion, relative peripheral refractions, measured in-vivo, were independent of the contact lenses central corrective power. The SOK contact lenses demonstrated a stronger capability in rendering relative peripheral myopic defocus into far periphery, compared to the other lens designs used in this study. This was accompanied by higher amounts of introduced astigmatic retinal image blur

Theory of Sound Field Synthesis

PDF version of the Theory of Sound Field Synthesis presented at http://sfstoolbox.org/en/3.0/