Far Field Diffraction Phenomena on Cylindrical Objects of Small Diameter Taking into Account Their Reflective Properties

Abstract—The features of far field diffraction phenomena on cylindrical (metal) objects of small diameters (0.01–0.5 mm) are investigated taking into account their reflective properties within the framework of the Kirchhoff–Fresnel scalar theory of light diffraction. The calculations used a screen-type cylinder model (of zero thickness). The reflected far field component was calculated by the stationary phase approximation. It is shown that when using standard information processing algorithms (valid for screen-type objects), the effect of the reflected light wave leads to a noticeable measurement error proportional to the amplitude coefficient of light reflection from the cylinder surface. To reduce its influence, we propose an algorithm for determining the diameters of such objects with increased accuracy by appropriate processing of the diffraction pattern near the angles $\theta\ll\sqrt[3]{\lambda/R}$, where $\lambda$ is the light wavelength and $R$ is the cylinder radius. The obtained results can be used in the development of high-precision diffraction meters for thin cylindrical objects (wires, filaments, fibers).