Resumen: A rigorous and powerful theoretical framework is proposed to obtain systems of orthogonal functions (or shape modes) to represent optical surfaces. The method is general so it can be applied to different initial shapes and different polynomials. Here we present results for surfaces with circular apertures when the first basis function (mode) is a conicoid. The system for aspheres with rotational symmetry is obtained applying an appropriate change of variables to Legendre polynomials, whereas the system for general freeform case is obtained applying a similar procedure to spherical harmonics. Numerical comparisons with standard systems, such as Forbes and Zernike polynomials, are performed and discussed. Idioma: Inglés DOI: 10.1364/OE.24.005448 Año: 2016 Publicado en: OPTICS EXPRESS 24, 5 (2016), 5448-5462 ISSN: 1094-4087 Financiación: info:eu-repo/grantAgreement/ES/MINECO/FIS2014-58303-P Financiación: info:eu-repo/grantAgreement/ES/MINECO/MTM2014-52859 Tipo y forma: Article (Published version) Área (Departamento): Matemática Aplicada (Departamento de Matemática Aplicada)