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Development of phase retrieval algorithms for lens-free optical microscope

Grant number: 19/19793-7
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): November 01, 2019
Effective date (End): October 31, 2021
Field of knowledge:Physical Sciences and Mathematics - Physics - General Physics
Principal researcher:Sebastião Pratavieira
Grantee:Natália Portes de Oliveira
Home Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
Associated research grant:13/07276-1 - CEPOF - Optics and Photonic Research Center, AP.CEPID


The development of microscopy was central to the scientific progress, especially when it comes to the study of microscope structure, as well as the understanding of the dynamics that occurs in this scale. Since the microscopes propose to exceed the limitations of human vision, the managing and exploitation of this technique are regarded as a science in itself. Within the several existing models, the lens less or lens-free holographic microscope comes as an alternative to the traditional optical microscopes, this was possible thanks to digital holography driven by the technological evolutions in computer science. The application of this technique in microscopy demands image processing in order to reconstruct the holograms that were acquired. However, just like the traditional optical system, the digital ones also present the phase loss problem, a physical limitation from the sensors (or photographic films) that make it impossible to capture all the information of the light's electric field, thus it is necessary a numeric reconstruction of the phase that was lost. Therefore, the purpose of this project is to implement phase retrieval algorithms, in the Python programming language, to reconstruct the holograms for a lens less holographic microscope. For such task, there are different methods that can be applied, among them is the multi-heights method, which uses information from different planes of the light's electric field to approximate to an appropriate phase value, and the other one: multispectral method which, in summary, uses multiple wavelengths of light to calculate the hologram phase values. At the end of the project, we aim to be able to compare these two methods in efficiency and resolution of the system. (AU)