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Journal of Biomedical Optics • Open Access

Anisotropy-based robust focus measure for non-mydriatic retinal imaging
Author(s): Andres G. Marrugo; María S. Millán; Hector C. Abril Baez; Gabriel Cristóbal; Salvador Gabarda

Paper Abstract

Non-mydriatic retinal imaging is an important tool for diagnosis and progression assessment of ophthalmic diseases. Because it does not require pharmacological dilation of the patient's pupil, it is essential for screening programs performed by non-medical personnel. A typical camera is equipped with a manual focusing mechanism to compensate for the refractive errors in the eye. However, manual focusing is error prone, especially when performed by inexperienced photographers. In this work, we propose a new and robust focus measure based on a calculation of image anisotropy which, in turn, is evaluated from the directional variance of the normalized discrete cosine transform. Simulation and experimental results demonstrate the effectiveness of the proposed focus measure.

Paper Details

Date Published: 17 July 2012
PDF: 10 pages
J. Biomed. Opt. 17(7) 076021 doi: 10.1117/1.JBO.17.7.076021
Published in: Journal of Biomedical Optics Volume 17, Issue 7
Show Author Affiliations
Andres G. Marrugo, Univ. Politècnica de Catalunya (Spain)
María S. Millán, Univ. Politècnica de Catalunya (Spain)
Hector C. Abril Baez, Univ. Politècnica de Catalunya (Spain)
Gabriel Cristóbal, Consejo Superior de Investigaciones Científicas (Spain)
Salvador Gabarda, Consejo Superior de Investigaciones Científicas (Spain)

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