Managing the depth of focus in 3D imaging through controlled distortion of digital holograms

M. Paturzo; P. Memmolo; A. Finizio; P. Ferraro

doi:10.1117/12.855884

14 May 2010 Managing the depth of focus in 3D imaging through controlled distortion of digital holograms

M. Paturzo, P. Memmolo, A. Finizio, P. Ferraro

Proceedings Volume 7718, Optical Micro- and Nanometrology III; 771806 (2010) https://doi.org/10.1117/12.855884
Event: SPIE Photonics Europe, 2010, Brussels, Belgium

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.

Citation Download Citation

M. Paturzo, P. Memmolo, A. Finizio, and P. Ferraro "Managing the depth of focus in 3D imaging through controlled distortion of digital holograms", Proc. SPIE 7718, Optical Micro- and Nanometrology III, 771806 (14 May 2010); https://doi.org/10.1117/12.855884

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