Julia Lobera - Academia.edu (original) (raw)

Papers by Julia Lobera

Optics and Lasers in Engineering, 2020

Abstract Two are the main limitations of in-line holography: the twin image problem and the poor ... more Abstract Two are the main limitations of in-line holography: the twin image problem and the poor spatial resolution in the optical axis direction. The twin image problem can be solved with the introduction of an imaging lens and a knife-edge aperture located at its focal plane. In this work, a theoretical analysis of the axial resolution with and without aperture is provided from the perspective of the Optical Diffraction Tomography. Theoretical analysis and controlled experiments with the different recording options, demonstrate that a small tilt of the illumination beam, together with a centered rectangular aperture, is a key parameter as it improves the spatial resolution along the optical axis during the location and tracking of a particle field.

Digital Image Plane Holography (DIPH) has been used to record the flow behind a linear turbine bl... more Digital Image Plane Holography (DIPH) has been used to record the flow behind a linear turbine blade cascade installed in a transonic wind tunnel. Illuminating the flow with two double-cavity Nd-YAG lasers and using two digital cameras for image recording, a series of digital holograms were taken with one camera while standard PIV recordings were simultaneously taken with the second camera. Both the intensity as well as the phase distribution of the illuminated flow plane were recovered from the holograms. The intensity distribution was used for a standard Particle Image Velocimetry (PIV) evaluation using a time delay of 1 μs and the two velocity component results are compared with the PIV results obtained from the second camera recordings. The phase distribution was used for a digital speckle pattern interferometry (DSPI) evaluation using a time delay of about 50 ns, which provides out-of-plane velocity component data. Four laser pulses were used to provide the different time delay...

This paper shows the feasibility of applying digital image plane holography (DIPH) as a fluid vel... more 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

Measurement Science and Technology, 2008

Proceedings of SPIE, 2000

Fundamental limitations to the spatial resolution and flow volume that can be mapped using hologr... more Fundamental limitations to the spatial resolution and flow volume that can be mapped using holographic particle image velocimetry. [Proceedings of SPIE 4076, 90 (2000)]. Jeremy M. Coupland, Julia Lobera Salazar, Neil A. Halliwell. Abstract. ...

... flows with high-speed digital image plane holography Virginia R. Palero • Julia Lobera • M. P... more ... flows with high-speed digital image plane holography Virginia R. Palero • Julia Lobera • M. Pilar Arroyo Received: 16 July 2009 / Revised: 18 December 2009 / Accepted: 28 December 2009 / Published online: 20 January 2010 Ó Springer-Verlag 2010 ...

Applied optics, Jan 10, 2004

A technique that allows one to measure simultaneously the three velocity components in a fluid pl... more A technique that allows one to measure simultaneously the three velocity components in a fluid plane is presented. One obtains the quantitative information from only one holographic recording by combining two different reconstruction processes. As both processes use an interferometric comparison of two waves, we refer to this technique as dual holographic interferometry. The far-field fringe pattern that is obtained when reconstruction is made with an expanded laser beam allows one to determine the in-plane velocity components. The image-field fringe pattern that is obtained when a pointwise laser beam is used for reconstruction contains information about an out-of-plane velocity component. As the two reconstruction processes have different sensitivities, two different ways to combine them are proposed. The system has been demonstrated in a fluidlike solid object and in a convective flow.

Purpose: Computational fluid dynamics (CFD) modelling of patient-specific cerebral aneurysms (CAs... more Purpose: Computational fluid dynamics (CFD) modelling of patient-specific cerebral aneurysms (CAs) may help predicting in silico the formation, growth and rupture of CAs. Nevertheless, despite the widespread use of CFD by engineers to simulate pre-and post-treatment blood flow in patient-specific vasculatures, there are still uncertainties regarding the accuracy of hemodynamics simulations. The quantification of their accuracy could potentially get data derived from CFD simulations one step closer to their employment within the clinical practice. In this work we propose a benchmark case based on an in vitro aneurysm similar to the in vivo ones.

... 1 - Digital high speed holography for the measurement of the 3C-2D velocity field in confined... more ... 1 - Digital high speed holography for the measurement of the 3C-2D velocity field in confined flows Virginia R. Palero 1 , Julia Lobera 1 , Pilar Arroyo 1 1: Department of Applied Physics, I3A-University of Zaragoza, Zaragoza, Spain, palero@unizar.es ...

In Optical Diffraction Tomography (ODT) the refractive index is reconstructed from images with di... more In Optical Diffraction Tomography (ODT) the refractive index is reconstructed from images with different illuminating wavefronts. In most cases the Born approximation is assumed, although this limits the applicability of the technique to weak-scattering problems. In this work we examine the scattering problem from first principles beginning from the Helmholtz equation that governs scalar diffraction and wave propagation. We demonstrate

ABSTRACT Digital Speckle Pattern Interferometry is applied to analyze surface corrosion processes... more ABSTRACT 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 effects.

We describe a digital holography technique that, with the simplicity of an in-line configuration,... more We describe a digital holography technique that, with the simplicity of an in-line configuration, produces holograms where the real and virtual images are completely separated, as in an off-axis configuration. An in-line setup, in which the object is imaged near the sensor, is modified by placing a shifted knife-edge aperture that blocks half the frequency spectrum at the focal plane of the imaging lens. This simple modification of the in-line holographic configuration allows discriminating the virtual and real images. As a fluid velocimetry technique, the use of this aperture removes the minimum defocusing distance requisite and reduces the out-of-plane velocity measurement errors of classical in-line holography. Results with different test objects are shown.

ABSTRACT Digital Speckle Pattern Interferometry (DSPI) has been applied to measure shape of solid... more ABSTRACT 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.

Optics and Lasers in Engineering, 2020

Abstract Two are the main limitations of in-line holography: the twin image problem and the poor ... more Abstract Two are the main limitations of in-line holography: the twin image problem and the poor spatial resolution in the optical axis direction. The twin image problem can be solved with the introduction of an imaging lens and a knife-edge aperture located at its focal plane. In this work, a theoretical analysis of the axial resolution with and without aperture is provided from the perspective of the Optical Diffraction Tomography. Theoretical analysis and controlled experiments with the different recording options, demonstrate that a small tilt of the illumination beam, together with a centered rectangular aperture, is a key parameter as it improves the spatial resolution along the optical axis during the location and tracking of a particle field.

Digital Image Plane Holography (DIPH) has been used to record the flow behind a linear turbine bl... more Digital Image Plane Holography (DIPH) has been used to record the flow behind a linear turbine blade cascade installed in a transonic wind tunnel. Illuminating the flow with two double-cavity Nd-YAG lasers and using two digital cameras for image recording, a series of digital holograms were taken with one camera while standard PIV recordings were simultaneously taken with the second camera. Both the intensity as well as the phase distribution of the illuminated flow plane were recovered from the holograms. The intensity distribution was used for a standard Particle Image Velocimetry (PIV) evaluation using a time delay of 1 μs and the two velocity component results are compared with the PIV results obtained from the second camera recordings. The phase distribution was used for a digital speckle pattern interferometry (DSPI) evaluation using a time delay of about 50 ns, which provides out-of-plane velocity component data. Four laser pulses were used to provide the different time delay...

This paper shows the feasibility of applying digital image plane holography (DIPH) as a fluid vel... more 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

Measurement Science and Technology, 2008

Proceedings of SPIE, 2000

Fundamental limitations to the spatial resolution and flow volume that can be mapped using hologr... more Fundamental limitations to the spatial resolution and flow volume that can be mapped using holographic particle image velocimetry. [Proceedings of SPIE 4076, 90 (2000)]. Jeremy M. Coupland, Julia Lobera Salazar, Neil A. Halliwell. Abstract. ...

... flows with high-speed digital image plane holography Virginia R. Palero • Julia Lobera • M. P... more ... flows with high-speed digital image plane holography Virginia R. Palero • Julia Lobera • M. Pilar Arroyo Received: 16 July 2009 / Revised: 18 December 2009 / Accepted: 28 December 2009 / Published online: 20 January 2010 Ó Springer-Verlag 2010 ...

Applied optics, Jan 10, 2004

A technique that allows one to measure simultaneously the three velocity components in a fluid pl... more A technique that allows one to measure simultaneously the three velocity components in a fluid plane is presented. One obtains the quantitative information from only one holographic recording by combining two different reconstruction processes. As both processes use an interferometric comparison of two waves, we refer to this technique as dual holographic interferometry. The far-field fringe pattern that is obtained when reconstruction is made with an expanded laser beam allows one to determine the in-plane velocity components. The image-field fringe pattern that is obtained when a pointwise laser beam is used for reconstruction contains information about an out-of-plane velocity component. As the two reconstruction processes have different sensitivities, two different ways to combine them are proposed. The system has been demonstrated in a fluidlike solid object and in a convective flow.

Purpose: Computational fluid dynamics (CFD) modelling of patient-specific cerebral aneurysms (CAs... more Purpose: Computational fluid dynamics (CFD) modelling of patient-specific cerebral aneurysms (CAs) may help predicting in silico the formation, growth and rupture of CAs. Nevertheless, despite the widespread use of CFD by engineers to simulate pre-and post-treatment blood flow in patient-specific vasculatures, there are still uncertainties regarding the accuracy of hemodynamics simulations. The quantification of their accuracy could potentially get data derived from CFD simulations one step closer to their employment within the clinical practice. In this work we propose a benchmark case based on an in vitro aneurysm similar to the in vivo ones.

... 1 - Digital high speed holography for the measurement of the 3C-2D velocity field in confined... more ... 1 - Digital high speed holography for the measurement of the 3C-2D velocity field in confined flows Virginia R. Palero 1 , Julia Lobera 1 , Pilar Arroyo 1 1: Department of Applied Physics, I3A-University of Zaragoza, Zaragoza, Spain, palero@unizar.es ...

In Optical Diffraction Tomography (ODT) the refractive index is reconstructed from images with di... more In Optical Diffraction Tomography (ODT) the refractive index is reconstructed from images with different illuminating wavefronts. In most cases the Born approximation is assumed, although this limits the applicability of the technique to weak-scattering problems. In this work we examine the scattering problem from first principles beginning from the Helmholtz equation that governs scalar diffraction and wave propagation. We demonstrate

ABSTRACT Digital Speckle Pattern Interferometry is applied to analyze surface corrosion processes... more ABSTRACT 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 effects.

We describe a digital holography technique that, with the simplicity of an in-line configuration,... more We describe a digital holography technique that, with the simplicity of an in-line configuration, produces holograms where the real and virtual images are completely separated, as in an off-axis configuration. An in-line setup, in which the object is imaged near the sensor, is modified by placing a shifted knife-edge aperture that blocks half the frequency spectrum at the focal plane of the imaging lens. This simple modification of the in-line holographic configuration allows discriminating the virtual and real images. As a fluid velocimetry technique, the use of this aperture removes the minimum defocusing distance requisite and reduces the out-of-plane velocity measurement errors of classical in-line holography. Results with different test objects are shown.

ABSTRACT Digital Speckle Pattern Interferometry (DSPI) has been applied to measure shape of solid... more ABSTRACT 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.