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

  Articoli su Riviste JCR/ISI  (anno 2006)

Autori:  Striano V., Coppola G., Ferraro P., Alfieri D., Grilli S., De Nicola S., Finizio A., Pierattini G

Affiliazione Autori:  Istituto per la Microelettronica e Microsistemi, Sez. di Napoli, Via P. Castellino 111, 80131 Napoli, Italy; CNR - Istituto Nazionale di Ottica Applicata, Sez. di Napoli, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy; Istituto di Cibernetica "E. Caianiello" del CNR, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy; Istituto per la Microelettronica e Microsistemi, Sez. di Roma, Via del Fosso del Cavaliere 100, 00133, Roma, Italy; Università Mediterranea, Reggio Calabria, Italy

Riassunto:  Digital Holographic Microscopy (DHM) is an optical interferometric technique for not destructive testing of microelectro-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.

Rivista/Giornale:  PROCEEDINGS OF SPIE
Volume n.:  6341      Pagine da: U400  a: U405
Note:  Congress: Speckle06: Speckles, From Grains to Flowers in Nimes (Francia)
DOI: 10.1117/12.695465

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