Peculiarities of interference method for measuring the diameters of circular reflecting cylinders

A method of measuring the diameter of circular reflecting cylinders using the interference pattern which is formed when their surface is illuminated by a grazing plane monochromatic light beam. In the approximation of geometrical optics; the behavior of the recorded intensity distribution under inaccurate positioning of the cylinder measured has been studied, and it has been demonstrated that when the field is registered in a zone remote from its diametral plane, the criticity of the measuring scheme to longitudinal displacement of the object decreases noticeably. An analytical formula has been obtained which makes it possible to reconstruct the objects diameter by its interference pattern in the remote zone. For estimation of the influence of light diffraction on the interference field, an equivalent model of field formation has been built according to which it may be regarded as a result of interference of a plane monochromatic wave and two point sources - a "floating" (on the objects surface) one and a stationary one, with ray and Fresnel type radiation patterns accordingly. As a result of calculations, it has been demonstrated that light diffraction on the cylinder influences noticeable the interference pattern which has to be taken into account when estimating the diameters of reflecting cylinders by the interference method with a high accuracy.