## Physics & Astronomy ETDs

#### Publication Date

Fall 11-13-2019

#### Abstract

Scattering from randomly rough surfaces is a well-established sub area of electrodynamics. There remains much to be done since each surface and optical processes that may occur in within the scattering medium, and countless other scenarios, is different. There are also illumination models that describe lighting in a scene on the macroscopic scale where geometrical optics can be considered adequate. Of particular interest for us is the intersection of the physical scattering theories and the illumination models. We present two contributions: 1) A minimum of two independent images are needed since any opaque surface can be uniquely specified in terms of its outward-normal vector field. This required the development of a global, nonlinear, alternating optimization scheme to compute parameter estimates. It is shown that high accuracy estimates can be obtained. 2)The smooth emergence of geometrical optics from physical optics using a full wave electromagnetic solution of the 1D scattering problem. It is shown here that the geometrical optics limit is arrived at in a smooth transition from physical optics starting with the electric field integral equation by varying the size of roughness structures on the surface and calculating the scattering cross length . Starting from roughness features smaller than the incident wavelength and also considering the size of the surface fluctuations relative to the size of the surface, the scattered light patterns show expected wave behavior that gradually transitions to geometrical ray optics as the size of surface roughness features increases well beyond the wavelength.

#### Degree Name

Physics

#### Level of Degree

Doctoral

#### Department Name

Physics & Astronomy

#### First Committee Member (Chair)

Sudhakar Prasad

#### Second Committee Member

Keith Lidke

#### Third Committee Member

Elohim Becerra

#### Fourth Committee Member

Manel Martinez-Ramon

#### Language

English

#### Keywords

optics, BRDF, EFIE, optimization, nonlinear optimization, global optimization

#### Document Type

Dissertation

#### Recommended Citation

Antolin Camarena, Julian. "Electromagnetic analysis of bidirectional reflectance from roughened surfaces and applications to surface shape recovery." (2019). https://digitalrepository.unm.edu/phyc_etds/224