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Optical Engineering

New technique for ray aberration detection in Hartmanngrams based on regularized bandpass filters
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Paper Abstract

The Hartmann test is a well-known technique for testing large telescopes mirrors. The Hartmann technique samples the wavefront under analysis using a screen of a uniformly spaced array of holes located at the pupil’s plane. The traditional technique used to gather quantitative data requires the measurement of the centroid of these holes as imaged near the paraxial focus. The deviation from its unaberrated uniform position is proportional to the slope of the wavefront’s asphericity. The centroid estimation is normally done manually with the aid of a microscope or a densitometer. Traditional techniques for carrier frequency fringe analysis cannot be used to analyze Hartmanngrams because this pattern contains many spatial frequencies hard to eliminate using standard linear filters. Also due to the finite extent of the pupils, Fourier transform methods and convolution filters with large support are not well suited for the analysis. We propose a new technique based on regularized bandpass filters to detect the transverse aberration in Hartmanngrams. These filters are used to transform the distorted 2-D dot pattern of the Hartmanngram into two orthogonal linear-carrier phase-modulated cosinusoidal gratings. The resulting cosinusoidal fringe patterns are then well suited for the analysis using highly sensitive 2-D carrier frequency phase estimation techniques such as direct interferometry.

Paper Details

Date Published: 1 June 1996
PDF: 7 pages
Opt. Eng. 35(6) doi: 10.1117/1.600743
Published in: Optical Engineering Volume 35, Issue 6
Show Author Affiliations
Manuel Servin Guirado, Ctr. de Investigaciones en Optica, A.C. (Mexico)
Daniel Malacara-Hernandez, Ctr. de Investigaciones en Optica, A.C. (Mexico)
Jose Luis Marroquin Zaleta, Ctr. de Investigaciones en Optica (Mexico)
Francisco J. Cuevas-de-la-Rosa, Ctr. de Investigaciones en Optica (Mexico)

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