Digital holography has been applied to discriminate particles with different sizes in a capillary flow. With this objective, a specific matched filter, a Wiener Filter, has been applied to the complex amplitude distribution obtained from holograms recorded with a tilted illumination set-up. Different possibilities of applying such a filter have been considered, related to the Wiener Filter definition itself and to its application in a 3D or 2D approach. The tilted illumination set-up allowed us to generate a new 2D visualization of the 3D particle scattering that has been found very useful to help in understanding the difficulties in finding particle trajectories when particle tracking methods are applied.
The simultaneous presence of the real and virtual images in the hologram reconstruction is inherent in the in-line
holography. This drawback can be overcome with a shifted knife-edge aperture at the focal plane of the imaging lens.
The shifted aperture DIH produces holograms where the real and virtual images are completely separated. In this paper
we propose a modification of the shifted aperture DIH that allows recording two holograms simultaneously using one
camera, while retaining the simplicity of the in-line configuration and the advantage of the shifted-aperture strategy. As
in typical stereoscopy, the advantage of this configuration is limited by the angle between the two illuminating beams,
and therefore the aperture size. Some improvement on the out-of-plane resolution can be expected from a combined
analysis of the multiplexed holograms. In order to compare this technique with other in-line holographic configurations,
several experiments have been performed to study the spatial resolution along the optical axis. The capabilities of the
different techniques for characterizing the flow in a flexible and transparent model of a carotid bifurcation are also
True colour Denisyuk-type hologram recording of diffusing objects in Bayfol® HX 102 self-developing photopolymer has been studied. In a first stage, monochromatic Denisyuk holograms of a standard white diffuser (Spectralon) have been recorded using lasers with wavelengths 442, 532 and 633 nm to determine the optimum exposure that gives maximum efficiency. The recording of holograms from a diffusing object has the particularity that intermodulation noise due to interference between waves arriving from different object points reduces effective index modulation. A maximum effective efficiency of 80% has been reached for monochromatic recording. In a second stage, a set of experiments has been carried out to determine the adequate relation of exposure for the recording of a Denisyuk hologram of the standard white diffuser with the three lasers simultaneously to get the maximum efficiency for each wavelength. With the determined optimal exposure, a hologram of a polychromatic diffusing object has been recorded, obtaining a good visual coincidence between hologram and original object.