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Proceedings Paper

Managing the depth of focus in 3D imaging through controlled distortion of digital holograms
Author(s): M. Paturzo; P. Memmolo; A. Finizio; P. Ferraro
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Paper Abstract

In digital holography (DH) the hologram is recorded by a CCD while intensity and phase reconstruction are performed numerically. For imaging objects at different depths, holograms are numerically reconstructed in planes that are parallel to the hologram but at different distances 1. However, for objects having 3D extension or 3D shape, only some portions of the object can be in good focus in each of those planes 2-4. The limited depth of focus is affecting all optical and imaging systems. In classical optical microscopy the problem is resolved by scanning mechanically the 3D volume. By such a procedure it is possible to build-up a single image, named Extended Focus Image (EFI), in which all points of the object are in-focus 5. However, the problem remains unresolved for objects changing their shape during the measuring time (i.e. for dynamic events). Various solutions have been proposed adopting DH methods 6-10. In fact, since all DH methods are based on a single image acquisition, it is clear that those methods are useful for dynamic objects (i.e. objects that change their shape during the observation under the microscope). Here we show a new DH methods based on the hologram deformation 11. It has the advantage to be very simple and without additional computational efforts in respect to a standard reconstruction. The method is applied to maintain in focus the reconstructed image of a MEMS subjected to thermal load that changes its position during the hologram acquisition.

Paper Details

Date Published: 14 May 2010
PDF: 6 pages
Proc. SPIE 7718, Optical Micro- and Nanometrology III, 771806 (14 May 2010); doi: 10.1117/12.855884
Show Author Affiliations
M. Paturzo, CNR-Istituto Nazionale di Ottica Applicata (Italy)
P. Memmolo, CNR-Istituto Nazionale di Ottica Applicata (Italy)
A. Finizio, CNR-Istituto Nazionale di Ottica Applicata (Italy)
P. Ferraro, CNR-Istituto Nazionale di Ottica Applicata (Italy)

Published in SPIE Proceedings Vol. 7718:
Optical Micro- and Nanometrology III
Christophe Gorecki; Anand Krishna Asundi; Wolfgang Osten, Editor(s)

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