CALCULATION OF IMAGES OF THE VOLUMETRIC ASYMMETRIC ABSOLUTELY ABSORBING EDGE OF AN OBJECT IN COHERENT LIGHT
Yu. V. Chugui1,2,3
1Technological Design Institute of Scientific Instrument Engineering, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: Fresnel and Fraunhofer diffraction, Fourier optics, spatial filtering, images and spectra of 3D objects, volumetric edge, 3D dimensional inspection
Abstract
As applied to dimensional inspection of 3D objects, specific features of the formation images of a volumetric asymmetric absolutely absorbing edge, which is the main fragment of extended (in depth) plates of constant thickness, in the diffraction-limited projection system of images are analytically investigated. The structures and intensity profiles in images of the front and rear faces of the object are studied, respectively, with small and large apertures of the optical system for various relationships of the object bevel c , Fresnel zone size dd ~ ( l is the light wavelength and d is the object thickness), and angular aperture of the optical system . For the bevel , at a large depth of focus of the system, there is a shift in the intensity profile in the 3D edge images, which is proportional to the Fresnel zone and the bevel value. It is analytically shown that a clear image of either the front face (the rear face is in the shadow) or the rear face (the front face is shaded by the rear face) is observed in the plane conjugated with the front face in the case with large bevels ( ) and small apertures of the system. Formulas for the profile of rear face images are derived and investigated in the case of significant volumetric effects, where the depth of focus of the system is much smaller than the object thickness. The results of the calculations are in good agreement with the results of computer modeling.
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