Article
Ronchi test with variable-frequency rulings
Fecha
2009Autor
Salinas-Luna, J.
Granados-Agustin, F.
Cornejo-Rodriguez, A.
Luna, E.
Sanchez-Escobar, J.J.
Hernandez-Cid, J.M.
Institución
Resumen
We present a new method for testing an optical surface. It uses the Ronchi test with variable-frequency rulings and a liquid-crystal display. The rulings can be formed by substructuring the spacing of a Ronchi ruling or combining several classical Ronchi rulings in a single variable-frequency ruling. This change allows us to observe smaller defects on the surface, because it enlarges the spatial-frequency domain of the ruling, and a larger dynamic range of detection of the Ronchi test can be obtained instead of increasing the resolution of the detection of the Ronchi test by iteratively changing classical Ronchi rulings with higher line density. As a result, we have found that it is possible to measure defects on a optical surface that are of size 57 nm (λ/11). © 2009 Society of Photo-Optical Instrumentation Engineers.