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Title: Techniques for the production of high quality lenses by the utilisation of a knowledge based system
Author: Pitschke, Elmar
Awarding Body: University of the West of England, Bristol
Current Institution: University of the West of England, Bristol
Date of Award: 2012
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Abstract:
The rapid increase in the employment of optics-based technologies in modern life has spurred the search for lenses that exhibit exceptionally high optical accuracies, and yet are simple and cheap to manufacture. Currently, most complex lenses are based on multiple lens elements of spherical form, and it is common for a number of these spherical elements to be combined into a single optical objective. However, a characteristic of spherical lenses, spherical aberration, prevents the spherical lens from achieving perfect refraction and leads to distortion of the image at the focus point. It is for this reason that multiple spherical elements are generally necessary. Aspherical, sometimes referred to as free-form, lenses enable the incorporation of compensation for spherical aberration. Such aspherical lenses may exhibit a perfect focus, will be lighter in weight and will be smaller in size than equivalent multi-spherical objectives. However, the production of asphericallenses is complex, a consequence of their intricate shape. Research was undertaken to analyse the methods for producing lenses. In particular magnetorheological finishing was studied extensively. This process utilises a fluid that is stiffened under the influence of a magnetic fluid as the polishing agent. It is an extremely capable and adaptable process, but yet is subject to many complex factors that influence the manner in which it may be applied to the optical finishing process. The magnetorheological finishing process was investigated, and procedures for synthesising the machine characteristic, referred to as the influence function, were proposed. Employment of the technique that was developed will reduce the quantity of optical material used for testing and machine characterisation, so reducing scrap, while saving the manufacturing time that must normally be devoted to the characterisation operation. In addition, a knowledge-based system was established, which may provide guidance and direction as to the most appropriate lens-processing conditions to adopt. The results of this work have generic applications, in diverse processes, wherever surface preparation and surface finishing are required
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.572873  DOI: Not available
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