In this dissertation, the development of alternative fiber based polishing tools for the finishing of precision freeform and aspherical optics is introduced. Freeform and aspherical optics, i.e. optics with varying radius of curvatures (ROC), are the current forefront for solutions for modern optical systems, enabling more compact and higher performance designs than possible with systems composed of classical optical components, i.e. planar and spherical optics. The technological challenges associated with the fabrication of freeform optics include; (1) identification of suitable tooling capable of accommodating the different ROC’s, and (2) achieving surfaces with low mid spatial frequency (MSF) error content. The mainstream fabrication techniques for freeform optics heavily rely on a process called sub-aperture polishing, whereby a tool (down to 1/10th of the optic size), is programmatically traversed across the surface to finish the part. This technique, due to the remnant tool path marks, results in MSF errors on the optic’s surface. Removal of MSF errors is an ongoing challenge in the optics industry. As the main contribution of this work, it will be shown that fiber based tools, which have the flexibility to conform to varying ROCs, have the potential to remove preexisting MSF errors. The other contributions of this work are as follows: (1) Favorable fiber characteristics for use in the proposed fiber based tools are isolated. (2) The material removal mechanism associated with fiber based tools is described. (3) Finite element models (FEM) are created to gain insights on the fundamental fiber-workpiece interaction, and on the fiber properties and geometries most suited for MSF reduction. (4) The initial steps of implementing fiber based tools in commercial, multi axis optic finishing machines are completed and the associated challenges identified.
In summary, this work lays the foundation for using fiber based tools to reduce MSF’s on freeform surfaces, and in doing so, the work addresses a critical need as identified by the optical fabrication community.
|Advisor:||Mullany, Brigid A.|
|Commitee:||Cherukuri, Harish P., Evans, Christopher J., Kazemi, Mohammad, Williams, Wesley|
|School:||The University of North Carolina at Charlotte|
|School Location:||United States -- North Carolina|
|Source:||DAI-B 79/09(E), Dissertation Abstracts International|
|Subjects:||Mechanical engineering, Optics|
|Keywords:||Fiber based tools, Freeform optics, Metrology, Mid spatial frequency, Polishing, Surface finish|
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