Daniel S. F. Magalhães

Holo-television system with a single plane

We show a system capable of projecting a video scene onto a white-light holographic screen to obtain a kind of image that results in a plane in front of the screen. This holographic screen is mainly a diffractive lens and is constructed by holography. The image plane can be located at any azimuth angle and seen with continuous parallax and without the use of goggles or any special visualization equipment. The image is not volumetric, but when the plane is oblique to the observer its appearance looks very close to a real volumetric image.

Construction of white-light holographic screens

Abstract In this paper we describe one setup employed for the recording of two types of holographic screens that can be used in white-light applications. We show how to obtain holographic screens with areas up to 1370 cm 2 and diffraction efficiency of 17%. We analyze the holographic screens in their relevant aspects as to focal lengths, theoretical approach, sizes and diffraction efficiencies specifying when each type is appropriate for particular applications.PACS 090.0090 090.1970 090.2890Keywords: holography, holographic screen, three-dimensional imaging 1. Introduction The holographic screen 1 is a diffractive optical element (DOE) constructed by holographic techniques in order to obtain the highest directionality such that one projected image can be seen in strictly one direction, while many images can be seen projected simultaneously. It is primarily a holographically-made lens where the vertical and/or horizontal observers field is extended, allowing for a more comfortable posture of the observer. The term “holographic screen” is used sometimes in a popular way to designate translucent screens that are used for image projections which produce a phantasmagoric two-dimensional image at the plane of the screen. These screens can be holographically constructed or by other methods. The holographic screens that we will describe here are

Pseudoscopic white-light imaging by means of two bi-dimensional diffracting elements and a pinhole

Diffracted images with inverted depth were first reported by the authors where a lens or slit intermediated the white-light double diffraction process. The diffracting elements were simple straight line diffraction gratings and the image could be seen but not projected due to its strong astigmatism. The generalization of the symmetry properties to bi-dimensionally defined diffracting elements allows to produce projected images with circular gratings intermediated by a pinhole. Acting as a focusing element, the possibility of enlargement is reported here with experimental results.

Haciendo hologramas en la escuela y en la casa

La comunidad cientifica que se ocupa de los problemas relacionados con el proceso de ensenanza-aprendizaje de la fisicas, ha dedicado muchos esfuerzos en los ultimos anos al perfeccionamiento del mismo, motivado en primera instancia, por las demandas de renovacion que el impetuoso desarrollo cientifico-tecnico le impone en la actualidad a la ensenanza de las ciencias. En los ultimos anos se ha producido un desarrollo vertiginoso en la fabricacion de diodos laser que emiten en el espectro visible, esto ha permitido su utilizacion creciente en multiples aplicaciones y hace factible su utilizacion en la ensenanza aprendizaje de la fisica universitaria y en particular de la holografia, por sus grandes ventajas frente a los laseres convencionales de gran costo y dificil manipulacion. En el trabajo se describen la instalacion experimental portatil disenada para la obtencion de hologramas en la escuela y en la casa con la utilizacion de diodos laser, la metodologia de trabajo a seguir, los metodos de procesamiento utilizados para diferentes tipos de emulsiones holograficas y un analisis de los defectos que pueden presentar los hologramas producidos y la forma de detectarlos y erradicarlosDepartamento de Fisica, Instituto Superior Politecnico Jose Antonio Echeverŕia, Ciudad de la Habana, Cuba Instituto de Fisica, Universidade Estadual de Campinas, Campinas SP, Brasil Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, SP, Brasil Departamento de Ciencias Basicas, Facultad de Ingenieŕia, Universidad Libre de Colombia, Bogota, Colombia Recebido em 28/10/2009; Aceito em 11/12/2009; Publicado em 17/2/2011

Imaging with two spiral diffracting elements intermediated by a pinhole.

A pseudoscopic (inverted depth) image made with spiral diffracting elements intermediated by a pinhole is explained by its symmetry properties. The whole process is made under common white light illumination and allows the projection of images. The analysis of this projection demonstrates that the images of two objects pointing away longitudinally have the main features of standard pseudoscopic image points. An orthoscopic (normal depth) image has also been obtained with the breaking of the symmetry conditions.

El holograma y su utilización como un medio de enseñanza de la física en ingeniería

With the emergence and development of the white-light holograms, new possibilities were created for its utilization as a teaching tool due to the characteristic of producing a three-dimensional image which constitutes an optical duplicate of the object. In this work the distinctive aspects of the hologram are described and its utilization is analyzed in engineering courses, through the design and construction of a Didactic Exhibition of Holography.Con el surgimiento de los hologramas reconstruibles con luz blanca y su desarrollo posterior, se abrieron grandes posibilidades para su utilizacion como medio de ense~nanza por la caracter¶‡stica de producir una imagen tridimensional que constituye un duplicadode un objeto. En el trabajo se describen las caracter¶‡sticas distintivas del holograma como un medio de ense~nanza de la f¶‡sica y se analiza su utilizacion en carreras de ingenier¶‡a, mediante la fundamentacion, el dise~no y construccion de una Exposicion Didactica de Holograf¶‡a creada para este proposito. Palavras-chave: holograma, medio de ense~nanza, f¶‡sica, exposicion didactica. With the emergence and development of the white-light holograms, new possibilities were created for its utilization as a teaching tool due to the characteristic of producing a three-dimensional image which constitutes an optical duplicate of the object. In this work the distinctive aspects of the hologram are described and its utilization is analyzed in engineering courses, through the design and construction of a Didactic Exhibition of Holography.

A Brazilian original pedagogical approach to the teaching of neurology

UNLABELLED The two-arm Clinical Decisions/Diagnostic Workshop (CD/DW) approach to undergraduate medical education has been successfully used in Brazil. OBJECTIVE Present the CD/DW approach to the teaching of stroke, with the results of its pre-experimental application and of a comparative study with the traditional lecture-case discussion approach. METHOD Application of two questionnaires (opinion and Knowledge-Attitudes-Perceptions-KAP) to investigate the non-inferiority of the CD/DW approach. RESULTS The method was well accepted by teachers and students alike, the main drawback being the necessarily long time for its completion by the students, a feature that may better cater for different educational needs. The comparative test showed the CD/DW approach to lead to slightly higher cognitive acquisition as opposed to the traditional method, clearly showing its non-inferiority status. CONCLUSION The CD/DW approach seems to be another option for teaching neurology in undergraduate medical education, with the bonus of respecting each learner`s time.

3D brain MR angiography displayed by a multi-autostereoscopic screen

The magnetic resonance angiography (MRA) can be used to examine blood vessels in key areas of the body, including the brain. In the MRA, a powerful magnetic field, radio waves and a computer produce the detailed images. Physicians use the procedure in brain images mainly to detect atherosclerosis disease in the carotid artery of the neck, which may limit blood flow to the brain and cause a stroke and identify a small aneurysm or arteriovenous malformation inside the brain. Multi-autostereoscopic displays provide multiple views of the same scene, rather than just two, as in autostereoscopic systems. Each view is visible from a different range of positions in front of the display. This allows the viewer to move left-right in front of the display and see the correct view from any position. The use of 3D imaging in the medical field has proven to be a benefit to doctors when diagnosing patients. For different medical domains a stereoscopic display could be advantageous in terms of a better spatial understanding of anatomical structures, better perception of ambiguous anatomical structures, better performance of tasks that require high level of dexterity, increased learning performance, and improved communication with patients or between doctors. In this work we describe a multi-autostereoscopic system and how to produce 3D MRA images to be displayed with it. We show results of brain MR angiography images discussing, how a 3D visualization can help physicians to a better diagnosis.

Fazendo imagens com um simples elemento difrativo ou refrativo: o axicon

In this previously divulgated paper [1] we demonstrate that the light diffracted by a simple compact disc can be used to generate images with interesting basic attributes. We compare this attributes with the ones obtained with refractive elements. A compact disc acts as an axicon that generates a diffraction-free beam and, because the focused position of the image depends on the wavelength of the diffracted light, thus it can be useful as a spectral filter. The experiments are of easy reproduction, allowing the understanding of images that the students observe daily at school or at home.

La física en la extensión universitaria a través de la holografía como medio de educación social

With the emergence and development of the white-light holograms, new possibilities were created for its utilization as a social education medium due to the characteristic of producing a three-dimensional image which constitutes an optical duplicate of the object. The paper describes the merits and characteristics of the hologram as a means of social education and experience in the construction and use of permanent holographic exhibitions in museums and traveling in the community as a result of university extension from physics.