Refocusing criterion via sparsity measurements in digital holography

Year: 2014

Authors: Memmolo P., Paturzo M., Javidi B., Netti P.A., Ferraro P.

Autors Affiliation: Center for Advanced Biomaterials for Health Care@CRIB, Istituto Italiano di tecnologia, Largo Barsanti e Matteucci 53, 80125 Napoli, Italy;
CNR-Istituto Nazionale di Ottica, via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy;
ECE Department, University of Connecticut, U-157, Storrs, Connecticut 06269, USA
ECE Department, University of Connecticut, U-157, Storrs, Connecticut 06269, USA.

Abstract: Several automatic approaches have been proposed in the past to compute the refocus distance in digital holography (DH). However most of them are based on a maximization or minimization of a suitable amplitude image contrast measure, regarded as a function of the reconstruction distance parameter. Here we show that, by using the sparsity measure coefficient regarded as a refocusing criterion in the holographic reconstruction, it is possible to recover the focus plane and, at the same time, establish the degree of sparsity of digital holograms, when samples of the diffraction Fresnel propagation integral are used as a sparse signal representation. We employ a sparsity measurement coefficient known as Gini’s index thus showing for the first time, to the best of our knowledge, its application in DH, as an effective refocusing criterion. Demonstration is provided for different holographic configurations (i.e., lens and lensless apparatus) and for completely different objects (i.e., a thin pure phase microscopic object as an in vitro cell, and macroscopic puppets) preparation.

Journal/Review: OPTICS LETTERS

Volume: 39 (16)      Pages from: 4719  to: 4722

More Information: We are very grateful to Dr. Andrea Finizio for acquiring the holograms of the mouse’s cell and the astronaut puppet. This work was supported by Progetto Bandiera La Fabbrica del Futuro in the framework of the funded project Plastic lab-on-chips for the optical manipulation of single cells (PLUS).
KeyWords: digital holography; image analysis; image reconstruction techniques; amplitude analysis; microscopy
DOI: 10.1364/OL.39.004719

Citations: 108
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