Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.763035
Title: Numerical methods for the manufacture of optics using sub-aperture tools
Author: Messelink, W. A. C. M.
ISNI:       0000 0004 7659 8176
Awarding Body: UCL (University College London);
Current Institution: University College London (University of London)
Date of Award: 2015
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Abstract:
Moore's law, predicting a doubling of transistor count per microprocessor every two years, remains valid, demonstrating exponential growth of computing power. This thesis examines the application of numerical methods to aid optical manufacturing for a number of case-studies related to the use of sub-aperture tools. One class of sub-aperture tools consists of rigid tools which are well suited to smooth surfaces. Their rigidity leads to mismatch between the surfaces of tool and aspheric workpieces. A novel, numerical method is introduced to analyse the mismatch qualitatively and quantitatively, with the advantage that it can readily be applied to aspheric or free-form surfaces for which an analytical approach is difficult or impossible. Furthermore, rigid tools exhibit an edge-effect due to the change in pressure between tool and workpiece when the tool hangs over the edge. An FEA model is introduced that simulates the tool and workpiece as separate entities, and models the contact between them; in contrast to the non-contact, single entity model reported in literature. This model is compared to experimental results. Another class of sub-aperture processes does not use physical tools to press abrasives onto the surface. A numerical analysis of one such process, Fluid Jet Polishing, is presented - work in collaboration with Chubu University. Numerical design of surfaces, required for generating tool-paths, is investigated, along with validation techniques for two test-cases, E-ELT mirror segments and IXO mirror segment slumping moulds. Conformal tools are not well suited to correct surface-errors with dimensions smaller than the contact area between tool and workpiece. A method with considerable potential is developed to analyse spatial-frequency error-content, and used to change the size of the contact area during a process run, as opposed to the constant-sized contact area that is state-of-the-art. These numerical methods reduce dependence on empirical data and operator experience, constituting important steps towards the ultimate and ambitious goal of fully-integrated process-automation.
Supervisor: Walker, D. D. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.763035  DOI: Not available
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