Diogo Soga

Single-exposure, photorefractive holographic surface contouring with multiwavelength diode lasers.

We studied the use of multiwavelength diode lasers for surface profilometry through holographic recording in sillenite Bi12TiO20 crystals. When such lasers are used, the holographic image from single-exposure recordings appears covered with interference fringes providing information on the surface relief of the object. By taking advantage of the narrow interference fringes due to the multiwavelength emission of the laser, we obtained interferograms by holographic recording with two reference beams, which improves the surface analysis by visual inspection and enhances the profilometry sensitivity.

Digital speckle correlation for nondestructive testing of corrosion

This paper describes the use of optical correlation speckle patterns to detect and analyze the metallic corrosion phenomena, and shows the experimental set-up used. We present some new results in the characterization of the corrosion process using a model based in electroerosion phenomena. We also provide valuable information about surface microrelief changes, which is also useful in numerous engineering applications. The results obtained are good enough for showing that our technique is very useful for giving new possibilities to the analysis of the corrosion and oxidation process, particularly in real time.

Real-time holographic interferometry using photorefractive Sillenite crystals with phase-stepping technique

This work applies a holographic interferometer setup that it uses the photorefractive Bi12SiO20 crystals for Real-Time Holographic Interferometry (RTHI) in diffusive regimen with configuration exhibiting difraction anisotropy. This device is connected with an interferogram-analysis method that uses the phase-stepping technique for quantitative measurement of changes on object. So we captured holographic interferograms from test surface, and calculated the phase map, using images by Four-Frame Method, and removed the wrapping of tangent function (unwrapping), using the Cellular-Automata Technique. We are obtained good results in applications in basic research, dentistry and technological areas.

Looking to the blue sky with colored patterns

This work presents a simple alternative technique to observe the polarization of the skylight on Earth. Using a birefringent material and a polarizer to look at the polarized light from the blue sky, it is possible to see a colored pattern that is associated to the birefringence of the material and the polarized light. Three different ways to polarize the light are also discussed in the context of the proposed experiment. Keywords: Blue sky, Rayleigh scattering, birefringence, polarization, education.

Contribución de la física al desarrollo de habilidades investigativas en estudiantes de ingeniería

Scientific research is essential to improve the quality of future specialists, due to the high rate of development of science and technology which professionals have to respond creatively to the problems of greatest relevance and importance. Developing scientific thinking is one of the purposes of Higher Education and it is responsibility of all the disciplines that compose a career. Among the main functions of a university professor is their ability to use the results of the research to form the student. The scientific research should be an academic requirement since the early years of career, as part of integral formation of students. This work shows the achieved results of the Physical discipline in the development of student scientific work with students of the Biomedical Engineering career at the Instituto Superior Politecnico Jose Antonio Echeverria, significantly increasing the number of students participating in scientific research and their motivation for this, the activity of independent and creative work and making the link between knowledge and practice as well as the integration with other disciplines of the career.

Dynamical speckles patterns of action potential transmission effects in squid giant axon membrane

Undoubtedly the most important result of the investigations in physiology and biophysics was the discovery of the electrochemical mechanism of propagation of the action potential in nerves that was made by Hodgkin and Huxley during the first half of the past century. Since some decades ago diverse experiments about the electro optical properties of the axon membrane there was published using the most diverse optical experimental procedures6-10. In this paper some results of a dynamical speckle technique applied for obtaining microscopic images of a section of a squid giant axon membrane during the activation by electrical impulses and his digital process are presented.

Digital Holographic Microscopy applied in the obtainment of hematological parameters in healthy and unhealthy individuals

The Digital Holographic Microscopy was applied to obtain hematological parameters in healthy and unhealthy individuals. The parameters analyzed were: mean corpuscular volume, mean corpuscular hemoglobin and the concentration of the mean corpuscular hemoglobin.

Alternative Reconstruction Method and Object Analysis in Digital Holographic Microscopy

Holography is a method for storing and reconstructing both amplitude and phase information of a wave front. In digital holography the reconstruction process is accomplished by means of a computer (Yaroslavsky & Merzyalov, 1980) obtaining directly the phase distribution of the object wave front. Particularly with the improvement of the spatial resolution of CCD cameras and the increasing computational performance of personal computers digital holography has been widely applied in many fields such as deformation analysis (Schedin et al., 2001), object contouring (Wagner et al., 2000), microscopy (Takaki & Ohzu, 1999) and particle measurement (Murata & Yasuda, 2000). The technique of digital holography has been implemented in a configuration of an optical microscope (Schilling et al., 1997); the objective lens produces a magnified image of the object and the interference between this image and the reference beam is achieved by the integration of the microscope into one of the arms of a Mach-Zender interferometer. This configuration is called Digital Holographic Microscopy (DHM). DHM is a powerful technique for real-time quantitative phase contrast imaging, since a single intensity image, called a hologram, allows the reconstruction of the phase shift induced by a specimen. This property of holograms offers phase-contrast techniques, which can then be used for quantitative 3D imaging (Palacios et al., 2005). Quantitative phase imaging is important because it allows the determination of the optical thickness profile of a transparent object with sub-wavelength accuracy (Yu et al., 2009). Through numerical processing of the hologram one can filter out parasitic interferences and the components of the image reconstruction: zero-order and twin image terms (Cuche et al., 2000) or to compensate for curvature introduced by the microscope objective (MO) (Pedrini et al., 2001),

Holographic interferometry techniques using photorefractive crystals of sillenite family Bi12SiO20 (BSO) and their applications in analysis of surfaces

The Holographic interferometry is a non-destructive testing of analysis on surfaces in basic research, technological and biomedical fields. However, the holographic interferometry techniques in real-time with conventional materials present serious difficulties. The photorefractives crystal are present as an attractive holographic recording medium. The phenomenon that characterizes these crystals in the photorefractive effect, consists of the refractive index modulation through photo-induced and linear electro-optic effect, allows the register of holograms of phase. Also it presents advantages as in situ self-proceeding of the recording medium and its indefinite reusability, i.e. it does not present fatigue. Thus, the objective of this work is the development of a holographic interferometer that uses the photorefractive crystal of the selenite family Bi12SiO20 as holographic recording medium. In this direction, we search to characterize BSO crystal determining some figures of merit in diffusive regime and drift regime. The holographic techniques of metrology are presented in three methods: real time holographic interferometry, double- exposure holographic interferometry, and time-average holographic interferometry had been studied with some applications in analysis of statics and dynamics processes on surfaces.

Nondestructive study of corrosion by the analysis of diffused light

This work describes the application of mean intensity diffusion analysis to detect and analyze metallic corrosion phenomena. We present some new results in the characterization of the corrosion process using a model based in electroerosion phenomena. Valuable information is provided about surface microrelief changes, which is also useful for numerous engineering applications. The quality of our results supports the idea that this technique can contribute to a better analysis of corrosion processes, in particular in real time.