Anisotropy-based robust focus measure for non-mydriatic retinal imaging

Andres G. Marrugo; María S. Millán; Hector C. Abril Baez; Gabriel Cristóbal; Salvador Gabarda

doi:10.1117/1.JBO.17.7.076021

17 July 2012 Anisotropy-based robust focus measure for non-mydriatic retinal imaging

Andres G. Marrugo, María S. Millán, Hector C. Abril Baez, Gabriel Cristóbal, Salvador Gabarda

Author Affiliations +

Journal of Biomedical Optics, Vol. 17, Issue 7, 076021 (July 2012). https://doi.org/10.1117/1.JBO.17.7.076021

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.

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Andres G. Marrugo, María S. Millán, Hector C. Abril Baez, Gabriel Cristóbal, and Salvador Gabarda "Anisotropy-based robust focus measure for non-mydriatic retinal imaging," Journal of Biomedical Optics 17(7), 076021 (17 July 2012). https://doi.org/10.1117/1.JBO.17.7.076021

Published: 17 July 2012

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KEYWORDS

Fermium

Frequency modulation

Eye

Cameras

Anisotropy

Imaging systems

Retinal scanning

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