The inspection of geometrical parameters of through holes with different configurations is one of the urgent tasks in
industry. The majority of the existing noncontact inspection methods doesn't allow measuring the holes of complicated
(noncylindrical) configurations with good performances. Two simple developed methods based on diffractive optical
elements (DOEs) make possible to inspect the through holes (with the diameter from 5 to 100 mm) both cylindrical and
complicated configurations with acceptable lateral and axial (longitudinal) resolution. First method, based on the
scanning of inner hole surface by light ring, takes a mechanical displacement of the inspected article along its axis. The
second holes inspection method uses the DOE as the diffractive focuser, which generates N light rings simultaneously
along the hole axis with ring spacing &Dgr;z. In this case no need for mechanical displacement of inspected articles, output
image contains full measuring information about 3D article hole configuration. We have fabricated some binary DOEs
using circular laser writing system CLWS-300, developed and produced at the TDI SIE SB RAS. The obtained results
have been used under the development of universal automatic inspection system of nuclear reactors fuel assemblies
spacer grids.
The urgent problem for industrial inspection is non-contact precision measurement the diameters of circular reflecting
cylinders, namely, rolling bearing elements with diameter from 10 mm to 50 mm must be inspected with error no more
than 1 ìm. Diffraction method for measurement of diameters of circular reflecting cylinders is presented. Peculiarity of
this method is rather measurement gaps between two cylinder vertexes and two reference half-planes, than
measurement of cylinder diameter by direct Fraunhofer method. Equivalent model of formation of Fraunhofer
diffraction pattern by measurable object is developed. Using this model an algorithm of diffraction pattern processing
was suggested that allows determining gap between object edges and reference half-planes with error no more than 1ìm.
The novel results of the R & D activity of TDI SIE SB RAS in the field of the optical measuring and laser technologies,
for solving safety problems in atomic and oil industry, as well as in railway transport are presented. 3D profilometer
with submicron and nanometer resolution using Linnik white-light interferometer and testing results of industrial
system for measuring surface defects of fuel elements are given. The metrological characterization of a perspective
Fresnel method for high precision measuring the dimensions of objects is investigated. Results of development and
testing the industrial system prototype for 3D inspection of nuclear grid spacers with micron resolution based on DOE
structured illumination are presented. We have developed an optical structured light method and an optical-electronic
system for automatic noncontact distant measurements of wear and defects detection for a contact wire electro-supply
network. For permanent noncontact bearing position inspection of oil-drilling platforms on Sakhalin coast (Russia) we
have developed optical-electronic method and produce system SAKHALIN. Experimental results and technical
performances are presented.
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 ofthe influence oflight 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 ofcalculations, 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.
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