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.
Holographic techniques have been used to measure the shape and the radial deformation of a blood vessel model and a real sheep aorta. Measurements are obtained from several holograms recorded for different object states. For each object state, two holograms with two different wavelengths are multiplexed in the same digital recording. Thus both holograms are simultaneously recorded but the information from each of them is separately obtained. The shape analysis gives a wrapped phase map whose fringes are related to a synthetic wavelength. After a filtering and unwrapping process, the 3D shape can be obtained. The shape data for each line are fitted to a circumference in order to determine the local vessel radius and center. The deformation analysis also results in a wrapped phase map, but the fringes are related to the laser wavelength used in the corresponding hologram. After the filtering and unwrapping process, a 2D map of the deformation in an out-of-plane direction is reconstructed. The radial deformation is then calculated by using the shape information.
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
Digital Speckle Pattern Interferometry (DSPI) has been applied to measure shape of solid rough objects. A two
wavelength setup with one single recording has been applied. Spatial Phase Shifting techniques, with different carrier
fringes for each wavelength, have been used in order to produce a spatial multiplex. Selecting each aperture image in the
Fourier plane, the amplitude and the phase of the object beam is obtained for each wavelength. The subtraction of those
waves produces a wrapped phase map that can be considered a contour line map for a synthetic wavelength. The
technique has been applied in different material and the visibility of the fringes is observed. The possibilities and limits
of the technique have been analyzed.
The complete measurement of the blood velocity and the vein wall deformation is important in order to obtain the wall
shear stress distribution in blood vessels. This information would facilitate the diagnosis and treatment of some
In this work, endoscopy has been combined with high speed Particle Image Velocimetry (PIV) to obtain the flow
velocity inside a transparent vessel model and with digital holography to measure the vessel wall deformation. The use
of endoscopes presents different advantages: they allow the simultaneous illumination and imaging of the object under
inspection; the endoscopes can be moved as close as required and can be located anywhere to observe different regions.
They can be used for observing inside opaque vessels in an oblique way, where the image perspective distortion can be
High speed PIV and endoscopic PIV have been applied to evaluate the influence of an antithrombotic filter in the
velocity field inside an inferior vena cava (IVC) model. Endoscopic digital holography has been developed to measure
the wall deformation in vessel models with steady and pulsatile flows. The models present different flexibility and
opacity grades. Both the vessel model and the endoscope end are immersed in a refractive index matching liquid in order
to avoid distortions.
In this work endoscopy has been combined with high speed PIV and holographic interferometry for flow velocity and wall deformation measurement of different vessels. Endoscopes have been used for illumination and/or recording of PIV images and digital holograms. High speed PIV has been applied to evaluate the influence of an antithrombotic filter in a vena cava model flow. Qualitative wall deformation has been obtained using digital holography in a vein model and in a real sheep aorta.
Digital speckle pattern interferometry (DSPI) has been applied to analyze surface corrosion processes in a metallic sample immersed in a 0.1 M Cu(NO 3 ) 2 solution. The corrosion process induces changes in the surface and in the solution refractive index. A detailed analysis of the DSPI measurements has been performed to obtain a two-dimensional visualization of the surface changes and an evaluation of the refractive index changes of the solution. The possibilities of DSPI for measuring surface changes in these conditions have been analyzed.
In this work a new application of digital holography for the study of cardio vascular diseases is proposed. The
simultaneous measurement of the blood flow velocity and the vein wall deformation can be obtained by combining
digital holography and endoscopy. Endoscopes are used for the illumination and recording of digital holograms inside a
vein model. Two different endoscopes have been used in different vein models in order to test the technique
performance. Preliminary results of flow velocity and wall deformation are presented.
Digital Speckle Pattern Interferometry is applied to analyze surface corrosion processes in a metal sample immersed in a
corrosive solution. This work describes the analysis process and the problems that can appear due to changes in the
liquid solution. It has been performed a detailed analysis of the optical measurements to obtain a 2D visualization of the
surface changes and an evaluation of the influence of the index refraction changes in the evaluation of the corrosion
This paper presents a force plate specially designed for measuring ground reaction forces in small animals. Digital
Speckle Pattern Interferometry (DSPI) is used to measure the plate deformation produced by the animal. Elasticity theory
is used to obtain force magnitude and application position from the vertical displacement field measured with DSPI. The
force plate has been tested with static weights of 5g and 10g at various locations on the plate. Some experiments with
20g body weight transgenic mice are also reported.
This paper shows the feasibility of applying speckle techniques as a non-destructive evaluation of the performance of ceramic high temperature superconducting materials. Firstly, Digital Speckle Pattern Interferometry has been applied to test these materials during service, with the sample cooled to liquid nitrogen temperatures, to detect where a hot spot will be generated. Surface degradation due to humidity has also been studied. Speckle Photography, whose optical setup is simpler, has been selected for this study.
This paper shows the feasibility of applying digital image plane holography (DIPH) as a fluid velocimetry technique for simultaneous measurements of all three components of the velocity field. As a first approach DIPH has been set up to measure a single fluid plane. The recording apparatus is a digital speckle interferometer (DSPI) with spatial phase shifting (SPS). The speckle interferometer has an out-of-plane sensitivity and the off-axis reference beam produces a spatial modulation in the pattern (hologram) recorded by the CCD camera. From the interferometric and photographic analysis of the reconstructed object wave, the three velocity components in the fluid plane are obtained. The complex amplitude of the object wave is calculated by the application of a Fourier-transform method to the hologram. The phase change between two subsequent frames yields an out-of-plane component of the velocity field. The two in-plane components are obtained, as in digital speckle photography, by cross correlation of the reconstructed object wave's intensity. Some quantitative results in a Rayleigh-Benard convective flow are presented. In the final setup, angular multiplexing with coherence length control has been introduced in order to simultaneously measure the velocity fields in two fluid planes. Some preliminary results from the convective flow are presented.