Flatness measurement using a grazing incidence interferometer
N. Alcalá Ochoa*, G. Mendiola, and J.E.A. Landgrave
Centro de Investigaciones en Óptica, Apartado Postal 1–948, Leon, Guanajuato, México, *e–mail: alon@foton.cio.mx
Recibido el 12 de agosto de 2005
Aceptado el 30 de noviembre de 2006
Abstract
The purpose of this work is to report results of flatness measurements using a grazing incidence interferometer. We show that this interferometer provides enough accuracy to measure nominally flat polishing tools and rough surfaces. In order to calculate the deformation of the surface under test, an interferogram is analyzed with digital imaging techniques based on Fourier methods. We found experimentally that the entire surface topography can be recovered with errors lower than ~ 0.6 μm, or ~ λeqv/6, where λeqv = 3.6441 μm is the equivalent wavelength of the interferometer.
Keywords: Optical testing; interferometry; fringe analysis; laser applications.
Resumen
El propósito de este trabajo es el de reportar resultados de medición de planicidad usando un interferómetro de incidencia oblicua. Se muestra que este interferómetro proporciona la exactitud necesaria para medir la planicidad de herramientas de pulido y superficies rugosas. Con el propósito de evaluar las irregularidades de la superficie bajo prueba, el interferograma obtenido se analiza con técnicas de procesamiento digital de imágenes basadas en métodos de Fourier. Encontramos experimentalmente que la superficie completa se puede medir con errores menores a ~ 0.6 μm, o ~ λeqv/6, donde λeqv = 3.6441 μm es la longitud de onda equivalente del interferómetro.
Descriptores: Pruebas ópticas; intereferometría; análisis de franjas; aplicaciones de láseres.
PACS: 06.20.–f; 42.62.–b; 42.62.Cf
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Acknowledgements
The authors would like to express their gratitude to the members of the optical and the mechanical workshops at CIO, in particular to Carlos Perez Santos, and also to Zacarías Malacara Hernández, of the Optical Engineering Group, for their assistance in various tasks that were essential for the successful completion of this work.
References
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is the area of D. In our case, A is clearly the area under inspection.
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