Diameter estimation of cylinders by the rigorous diffraction model.
The Fraunhofer diffraction formula is commonly used for estimating the diameter of thin cylinders by far field diffractometry. However, an experimental systematic overestimation of the value of the cylinder diameter by this diffraction model and other three-dimensional models has been reported when this estimation is compared with those obtained from interferometric techniques. In this work, a rigorous electromagnetic diffraction model is analyzed to determine the cylinder diameter by using the envelope minima of the far field diffraction pattern. The results of this rigorous model are compared with those from the Fraunhofer diffraction formula. The overestimation by the Fraunhofer model is predicted theoretically, presenting a dependence on the wavelength, the polarization state of the incident wave, and the cylinder diameter. The discrepancies are shown to be due to the three-dimensional geometry.
Sanchez-Brea
Luis Miguel
LM
Applied Optics Complutense Group, Departamento de Optica, Universidad Complutense de Madrid, Escuela Universitaria de Optica, Arcos del Jalon s/n., 28037 Madrid, Spain. sanchezbrea@fis.ucm.es