Imaging 3-D Objects by Extending the Depth of Focus in Digital Holography

Abstract

Digital holography is an imaging technique offering both sub-wavelength resolution and real-time capabilities to record 3-D objects using the interference between an object wave and a reference wave captured by an image sensor such as a CCD array. The basic advantage of digital holography is that it can quantitatively extract the three-dimensional (3-D) information of the object from the numerical reconstruction of a single digitally recorded hologram [1,2,3]. Since the information of the optically interfering waves is stored in the form of matrices, the numerical reconstruction process enables full digital processing of the holograms and offers many more possibilities than conventional optical processing. It is possible to numerically focus on any section of the 3-D volume object without mechanical focusing adjustment. This opens the field to a variety applications, such as 3-D microscopic investigations and real-time imaging of biological specimens where wavelength-scanning digital interference holography [4] is used to reconstruct the 3-D volume from a set of scanning tomographic images, hybrid holographic microscopy [5], 3-D microscopy by optical scanning holography [6], phase shifting digital holog-