A new focus detection criterion in holograms of planktonic organisms

• Published in: Pattern recognition letters 2020-10, Vol.138, p.497-506
• Main Authors: Moreno, Gelaysi, Ascaneo, Jefferson S., Ricardo, Jorge O., De La Cruz, Leandro T., Arias, Yaumel, Strickler, J. Rudi, Lopes, Rubens M.
• Format: Article
• Language: English
• Subjects: Algorithms; Criteria; Digital holography; Focus detection; Holograms; Holographic reconstruction; Image quality; Mathematical models; Plankton; Quality assessment
• ISSN: 0167-8655; 1872-7344
• DOI: 10.1016/j.patrec.2020.08.004

•A new criterion for automatic focal plane identification in digital holographic reconstruction is proposed.•Three autofocusing metrics, luminance, definition and gradient variation, were evaluated individually and in combination.•The Q quality index, combining the three functions, was the most robust approach for automatic holographic reconstruction.•Plankton organisms with complex 3-D structures were efficiently reconstructed without the need of further manual refocusing. With the increased use of digital holography to observe biological events in three dimensions the need for autofocusing becomes essential. We introduced a modified image quality evaluation technique as a focus criterion in the reconstruction of digital holograms. The method employed was initially proposed by [Wang et al. (2008)] to evaluate image inpainting quality from three aspects: luminance, definition, and gradient similarity. We considered these criteria for automatic focusing, individually and in combination. Our numerical simulation and experimental results obtained from 96 holograms of planktonic organisms show that the combined approach provided more accurate results compared to the individual metrics. We propose the use of such combined criterion to implement autofocusing algorithms for serial holograms, such as from observations of performances of plankton behavior.