Improvement of the reconstruction algorithm for extended focus image of MEMS by digital holography

Valerio Striano; Giuseppe Coppola; Pietro Ferraro; Domenico Alfieri; Simonetta Grilli; Sergio De Nicola; Andrea Finizio; Giovanni Pierattini

doi:10.1117/12.695465

15 September 2006 Improvement of the reconstruction algorithm for extended focus image of MEMS by digital holography

Valerio Striano, Giuseppe Coppola, Pietro Ferraro, Domenico Alfieri, Simonetta Grilli, Sergio De Nicola, Andrea Finizio, Giovanni Pierattini

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Proceedings Volume 6341, Speckle06: Speckles, From Grains to Flowers; 63411T (2006) https://doi.org/10.1117/12.695465
Event: Speckle06: Speckles, From Grains to Flowers, 2006, Nimes, France

Abstract

Digital Holographic Microscopy (DHM) is an optical interferometric technique for not destructive testing of micro-electro-mechanical systems (MEMS). A characterization process based on a no-contact technique allows us to analyze deformations, warping, residual stress, cracks and more other defects of MEMS, without destroy them. The flexibility of this technique allows us to improve novel numerical reconstruction algorithm for the recovery of more information. The post processing of the acquired holograms allows to reduce noise, optical aberrations, defocusing. In particular, the hologram reconstruction process has been modified to obtain Extended Focus Images (EFI). In Digital holographic microscopy, the use of microscopy objectives with high magnifications, reduces the focus depth. This means that for extended object a single reconstructed image with all the details in focus is not possible to obtain. Using a multiple reconstruction process and opportune resizing algorithms a full focused reconstructed images of extended object has been obtained without any mechanical movement. In particular, the advantages of the EFI technique are unique for dynamical characterization by DHM of extended objects, where the techniques based on multiple acquisitions fail. The EFI technique has been applied to obtain a best focused reconstructed image and profile of some micromechanical systems. It is demonstrated that this new approach allows to improve the accuracy in the EFI image when compared to the previous experimental results. Focusing of zones at different quote has been obtained evidencing, shape, crack and deformation impossible to observe otherwise at the same time. Moreover, these technique of reconstruction and analysis can be advantageous in many other fields of application.

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Valerio Striano, Giuseppe Coppola, Pietro Ferraro, Domenico Alfieri, Simonetta Grilli, Sergio De Nicola, Andrea Finizio, and Giovanni Pierattini "Improvement of the reconstruction algorithm for extended focus image of MEMS by digital holography", Proc. SPIE 6341, Speckle06: Speckles, From Grains to Flowers, 63411T (15 September 2006); https://doi.org/10.1117/12.695465

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KEYWORDS

3D image reconstruction

Digital holography

Microelectromechanical systems

Reconstruction algorithms

Holograms

Holography

Microscopes

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