Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 35 for “"Zernike"”.
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Orthogonality and convergence of discrete Zernike polynomials
The Zernike polynomials are an infinite set of orthogonal polynomials over the unit disk, which are rotationally invariant. They are frequently utilized in optics, opthal- mology, and image recognition, among many other applications, to describe spherical aberrations and image features. …
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Clustering Analysis of Zernike Coefficients Through Quantile Regression
… clustering procedure to cluster fifteen Zernike coefficients into groups. Quantile regressions are considered to describe the relationship between Zernike coefficients and pupil size. We employ Gibbs sampler and adaptive rejection Metropolis sampling to infer the parameters for each …
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Clustering Analysis of Zernike Coefficients From High Order Aberration Patients
<p>This thesis focuses on clustering fifteen Zernike coefficients using the method of clustering of linear regression models (CLM). EM algorithm is used to infer the maximum likelihood estimate of parameters for each cluster. Bayesian information criterion (BIC) combined with Bootstrapped maximum …
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Modal Analysis of Axisymmetric Structures using Zernike Polynomials and Machine Learning
… manual and labor-intensive process. Leveraging Zernike Annular Moment Descriptors (ZAMD) as feature maps, supervised learning models, such as decision trees, random forests, and XGBoost, achieve a high classification accuracy, thus eliminating the need for manual intervention. Furthermore, …
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Performance analysis of functional expansion tallies on 2D PWR pin cell
… applications, the performance of FETs using a Zernike polynomial series has never been thoroughly tested. This work performs an analysis of Zernike-based FETs on a 2D PWR pin-cell geometry and compares the simulation time and accuracy with conventional histogram tallies for reaction rate …
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Fine surface control of flexible space mirrors using adaptive optics and robust control
… this, a new technique for model reduction using Zernike polynomials was developed. The H[infinity] controller was able to achieve a minimum 15 Hz control bandwidth. The previous integral controller was unable to meet the 10 Hz bandwidth requirement. The H[infinity] design process used was …
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Algorithms for the application of Hartmann-Shack wavefront sensors in ophthalmology
… In addition to a modal approach with Zernike Polynomials, alternative possibilities of representation of the wavefront with non-modal and heterogeneous procedures are presented. Within the framework of this thesis, extensive measuring software was developed. An additional program that …
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Tomographic Reconstruction of Wavefront Aberrations using Multiple Laser Guide Stars
… Modal decomposition of wavefront phase using Zernike polynomials is a widely used technique in adaptive optics (AO) research. However, this approach breaks down with the large number of degrees of freedom required by ELTs.This research proposes the use of an alternative basis, the disk …
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Fabrication of extremely smooth blazed diffraction gratings
… wavefront aberration functions known as the Zernike polynomials. The thin film stress is proved to be linearly related to the change of the Z₂₁ Zernike coefficient. The anisotropic material properties of silicon are taken into account in the derivation, and a prediction of lattice dependent …
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On The Use Of Gaussian Filter Functions For Adaptive Optics
… filter functions calculated using various Zernike modes can be useful in removing lower-order aberrations caused by atmospheric turbulence. Traditionally, these filter functions are calculated using the step function depicting a hard aperture that introduces integrals that are sometimes …
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MODEL-BASED 3-D VISION
… is proposed in this thesis. This method uses Zernike moment invariants of the silhouette of the unknown object to form a set of fuzzy-weighted quantities called fuzzy quaternions. The database of the models is generated by first creating the octree representation of the 3-D objects based on …
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Spatio–temporal analysis of changes of shape for constituent bodies within biomolecular aggregates
… unique modelling approach used is the method of Zernike moments. Zernike moments are an extension of spherical harmonics to include more general radial dependence and the ability to model holes, folded layers etc. within and on the unit sphere. The method has traditionally been used to describe …
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Image understanding and feature extraction for applications in industry and mapping
… geometric invariant moments, Legendre moments, Zernike moments and pseudo-Zernike moments. Two-dimensional Fourier transforms are also considered as pattern classifiers. The suitability of these techniques is assessed. These are then applied as object locators and as feature extractors or …
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Adaptive optics aberrometer and wavefront corrector using a twisted-nematic liquid-crystal on silicon chip
… that were carried out include the generation of Zernike wavefronts, measurements of Zernike coefficients of elements with known and unknown optical properties, as well as open- and closed-loop corrections of static and dynamic aberrations. Parameters such as experimental and simulated point …
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A low complexity representation of the coherent point spread function in the presence of aberrations and arbitrarily large defocus
… use of higher order Airy functions along with Zernike and Taylor expansions. Our approach is applicable when we are considering a finite, arbitrary number of aberrations and arbitrary large defocus simultaneously. We present an upper bound for the complexity and the convergence rate of this …
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A New Hybrid Diffractive Photo-mask Technology
… conditions, it is possible to characterize Zernike wave front aberration coefficients up to any desired order. And, the second application is the use of binary phase grating mask for analog micro-optics fabrication. This approach of using binary phase grating mask for fabricating analog …
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Adaptive Optik in der Zwei-Photonen-Mikroskopie
… möglich. Höchste Fluoreszenzintensität wird bei Zernike-Koeffizienten beobachtet, die deutlich unter den theoretisch vorhergesagten Werten liegen. Mögliche Gründe für diese Diskrepanz werden diskutiert.
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Computational imaging and automated identification for aqueous environments
… including a novel focus detector using local Zernike moments. Two methods for estimating lateral positions of objects in holograms without reconstruction are presented by extending a summation kernel to spherical references and using a local frequency signature from a Riesz transform. A new …
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Coherence-Gated Wave-Front Sensing in Strongly Scattering Samples
… measured wave-front with a linear combination of Zernike polynomials up to the fifth radial degree. The principle of CGWS is tested by measuring two wave-front aberrations, defocus and astigmatism, for a mirror as a sample and a strongly scattering sample. The results are compared to theoretical …
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Computational imaging and automated identification for aqueous environments
… including a novel focus detector using local Zernike moments. Two methods for estimating lateral positions of objects in holograms without reconstruction are presented by extending a summation kernel to spherical references and using a local frequency signature from a Riesz transform. A new …
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