MID-SPATIAL FREQUENCY CHARACTERIZATION AND SPECIFICATION FOR FREEFORM SURFACES USING ZERNIKE POLYNOMIALS
1 online resource (175 pages) : PDF
University of North Carolina at Charlotte
Mid-spatial frequency on freeform optical elements induces small-angle scatter and affects the optical performance. Fabrication techniques involved in making freeform surfaces leave tooling marks on the surface due to the sub-aperture nature of the fabrication process. In recent years, there has been a growing need for specification and characterization of the mid-spatial frequencies for freeform surfaces. There is a range of methods to consider for representing the mid-spatial frequency content: the power spectral density (PSD), the structure function (SF), and a polynomial basis representation such as Zernike and Forbes polynomials. Using research discussed here and published discussions from the literature, we compare a Zernike representation to a PSD representation, and structure-function representation in terms of ability to connect to optical performance, ability to connect to the fabrication process, and other practical considerations. Our focus is on investigating a Zernike polynomial representation for quantifying the mid-spatial frequency content in the height maps. We will illustrate how this polynomial representation captures certain characteristics of the mid-spatial frequency texture. A filtering aspect of these polynomials is also explored and optical performance is predicted based on very large orders of Zernike polynomials.
FREEFORM OPTICSMID SPATIAL FREQUENCYOPTICAL METROLOGYOPTICAL PERFORMANCESURFACE CHARACTERIZATIONZERNIKE POLYNOMIALS
Optical Science & Engineering
Evans, ChristopherSuleski, ThomasGbur, Gregory
Thesis (Ph.D.)--University of North Carolina at Charlotte, 2017.
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). For additional information, see http://rightsstatements.org/page/InC/1.0/.
Copyright is held by the author unless otherwise indicated.