UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2003 Meeting


Section: Optics, Spectroscopy, Plasma and Lasers


Title:
Nondestructive high sensitivity testing of optically rough materials using DOE


Authors:
Iuliana IORDACHE, Adrian TIMCU, Mihai OANE, Dan APOSTOL, Victor DAMIAN, Raluca MULLER1


Affiliation:
INFLPR, Bucharest / Romania

1 National Institute of Microtechnology


E-mail


Keywords:


Abstract:
Interferometry is still in our days the most precise method for measuring length straightness, flatness, roughness and some other geometrical characteristics of optical and high precision mechanical parts. Many methods were developed- interferometric optical set-ups, algorithms for fringe interpretations and dedicated software- having as a purpose the measurement of these geometrical parameters. Having in mind the large packet of information connected to shape measurement by interferometry sounds reasonable to use these methods to qualitatively test and measure not so sensitive small roughness surfaces. For this purpose is necessary to use a less sensitive interferometer, able to produce fringes on rough materials. Indeed the main problem in interferometry is to use coherent beams to interfere. Reflections on rough surface (mirror) are destroying the spatial coherence of the light beam making the interference impossible. A grating type interferometer [1] uses a grazing reflection on the testing part. In this case grazing reflectance could be very large and the projected roughness height on the incident light directions is small. We build such an interferometer using a diffractive optical element (DOE) realized in National Institute of Microtechnology. It is a 25mm diameter 100 lines/mm transmission nickel on glass grating. The corresponding incidence angle on the sample is very large ƒáƒn= 90o - ƒÑ= 88o 11¡¦ 24¡¦¡¦. We obtain resolvable quality fringes for different material from industrial quality metals to wood. Flatness map for a metallic flatness proof (caliber) and other different material and roughness mechanical parts will be presented using usual algorithm in interferometry. Reference: 1.Sven Brinkmann, 1998, Opt. Eng. 37(9), 2506-2511. 2. Diffractive Optics, 1999 ,EOS topical meeting on Diffractive Optics, Jena