Papers by Néstor Bolognini
Stereographic register of nonstatic objects through a speckle carrier
Proceedings of SPIE, Jul 1, 1990
ABSTRACT 3-D data display can be classified into holographic and non-holographic. (1]. Normally, ... more ABSTRACT 3-D data display can be classified into holographic and non-holographic. (1]. Normally, the amount of information stored in a hologram i very large. In this way, if only deph perception is required, the stereoscopic techniques provide an adequate 3-D display. Among the non-holographic method, we have developed an optical method for storing on a single recording plate different perspectives of a 3-D scene [2). In this paper we propose such stereoscopic method for displays of moving objects.
Experimental non-paraxial self-images
Latin America Optics and Photonics Conference, 2018
An experimental report of the Talbot effect at non-paraxial regime for a one dimensional amplitud... more An experimental report of the Talbot effect at non-paraxial regime for a one dimensional amplitude grating of period of 2μm is presented. Quasi and self-images were obtained with a confocal microscope, and these self-images are contrasted with those obtained by the scalar theory of diffraction in representation of plane waves.
Filtrado Espacial Con Cristales Bso
Se propone un metodo para operaciones de filtrado que utiliza un cristal fotorrefractivo en el pl... more Se propone un metodo para operaciones de filtrado que utiliza un cristal fotorrefractivo en el plano de Fourier de un procesador 4-f. El cristal actua como filtro al modificarse la birrefringencia inducida cuando se proyecta la imagen incoherente de una dada transparencia. En consecuencia se modifica el estado de polarizacion de la luz transmitida a traves del cristal. Se realiza un filtrado selectivo al introducir una combinacion de filtros y polarizadores.
Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales, Jun 28, 2018
En este trabajo se estudia el efecto Lau empleando redes de fase de volumen generadas en un crist... more En este trabajo se estudia el efecto Lau empleando redes de fase de volumen generadas en un cristal fotorrefractivo tipo BSO. En nuestra propuesta la red de fase objeto se genera mediante la proyección de la imagen de una red iluminada incoherentemente en el volumen del cristal. Para esta red de fase fotorrefractiva se define un parámetro de modulación que depende del espesor del cristal. Se presentan resultados teóricos para diferentes distancias entre redes objeto-fuente que confirman nuestra propuesta. © 2018. Acad. Colomb. Cienc. Ex. Fis. Nat. Palabras clave: Efecto Lau; Red de volumen; Cristales fotorrefractivos.
Optica Pura y Aplicada, 2017
The Talbot effect is a diffractive phenomenon which was found since its inception in the Gaussian... more The Talbot effect is a diffractive phenomenon which was found since its inception in the Gaussian optics, but when the period of the object is comparable with the wavelength is considered entering its non-paraxial regime. There, it has attracted interest for its applications related to the design of objects and their restorative effects posing in damaged gratings on this scale. In this contribution a study of this phenomenon at level non-paraxial (metaxial) is presented by using scalar diffraction theory in plane waves representation for periodic transversal fields. To this end, a one-dimensional amplitude grating of period p is used which is illuminated by a monochromatic plane wave of wavelength λ where p ranges between 1,5 λ and 4,2 λ.
Experimental realization of 3D clustered speckle field simulation: An approach to optical trapping
Frontiers in Optics 2011/Laser Science XXVII, 2011
Optimized characterization for a spatial light modulator under less restrictive operating conditions
AIP Conference Proceedings, 2008
An alternative way to easily find out the characterization parameter set which describes nematic ... more An alternative way to easily find out the characterization parameter set which describes nematic liquid crystal spatial light modulators (NLCSLM) is presented. By following a constraint set analysis, the successive elimination of superfluous sets finally leads to the proper values. It is shown that the availability of two wavelengths is enough to develop the procedures leading to a correct SLM
Optics Express, 2011
We introduce for the first time the concept of an all-optical encrypted movie. This movie joints ... more We introduce for the first time the concept of an all-optical encrypted movie. This movie joints several encrypted frames corresponding to a time evolving situation employing the same encoding mask. Thanks to a multiplexing operation we compact the encrypted movie information into a single package. But the decryption of this single package implies the existence of cross-talk if we do not adequately pre-process the encoded information before multiplexing. In this regard, we introduce a grating modulation to each encoded image, and then we proceed to multiplexing. After appropriate filtering and synchronizing procedures applied to the multiplexing, we are able to decrypt and to reproduce the movie. This movie is only properly decoded when in possession of the right decoding key. The concept development is carried-out in virtual optical systems, both for the encrypting and the filtering-decrypting stages. Experimental results are shown to confirm our approach.
El efecto fotorrefractivo consiste en un cambio reversible del índice de refracción, bajo ilumina... more El efecto fotorrefractivo consiste en un cambio reversible del índice de refracción, bajo iluminación no uniforme, que se presenta en materiales fotoconductores y que poseen efecto electro-óptico lineal. Estos cristales, son medios de registro volumétricos, y permiten poner en evidencia la naturaleza de volumen en los casos que la información a almacenar la tenga. En ese sentido, se estudiaron en distintos arreglos experimentales la influencia 3D de la información registrada. En todos ellos se emplearon cristales fotorrefractivos BSO que combinan respuesta en tiempo real, reversibilidad y alta sensibilidad en la región visible del espectro. Uno de los casos analizados, consistió en estudiar el registro y reconstrucción de distribuciones unidimensionales (redes de Ronchi) de baja frecuencia, registradas incoherentemente en un convertidor óptico fotorrefractivo. Se verificó un comportamiento característico de la holografía de volumen en transmisión a pesar de tratarse de un registro no holográfico. En la implementación se observó que para aumentar la selectividad angular, es conveniente emplear cristales de mayor espesor y redes de mayor frecuencia espacial. Sin embargo, este incremento está limitado por la resolución del sistema formador de imágenes. Es justamente la selectividad angular, la característica que permiten el almacenamiento múltiple sin solapamiento. Otro caso estudiado fue el de las autoimágenes generadas a partir de una red almacenada en un cristal fotorrefractivo. Las redes almacenadas tienen una naturaleza de fase y de volumen. Recordemos que una distribución de intensidad no uniforme queda replicada en el cristal como variaciones locales de birrefringencia del orden de 10-4. Una red plana de fase con esta modulación genera autoimágenes de baja visibilidad, sin embargo aquellas formadas a partir de las redes 3D fotorrefractivas presentan una alta visibilidad. Hemos encontrado una relación directa entre la visibilidad y el volumen del medio de registro. Asimismo, se verificó una dependencia de la visibilidad en términos de la profundidad de foco de la red incoherentemente almacenada cuanto del espesor del cristal. Otro arreglo en el cual se pone en evidencia las características volumétricas del medio de registro es el registro de patrones de patrones de speckle modulados. En este caso, se generan dentro del volumen del grano de speckle redes de índices. Hemos demostrado que la finitud de estas estructuras se traduce en un comportamiento particular de la eficiencia de difracción.
Fringe visibility control in DSPI by using a BSO crystal
A method for the visibility control in an interference fringe system is proposed. The experimenta... more A method for the visibility control in an interference fringe system is proposed. The experimental arrangement employs a BSO crystal as a passive element, which provides, by adjusting an external applied voltage, changes in the polarization states of the incident light, thus inducing the visibility variations. A theoretical explanation and experimental results are included
<title>Surface roughness measurement by speckle processing</title>
Optics in Complex Systems, 1990
ABSTRACT
<title>Real-time pseudocoloring of gray levels</title>
Optics in Complex Systems, 1990
ABSTRACT A new real-time pseudocoloring technique which employs photorefractive biased BSO crysta... more ABSTRACT A new real-time pseudocoloring technique which employs photorefractive biased BSO crystals and coherent or incoherent illumination is proposed.
Double-aperture speckle method using a BSO crystal for in-plane displacement
SPIE Proceedings, 1999
The possibility of using a BSO crystal as a recording medium of specklegrams with carrying freque... more The possibility of using a BSO crystal as a recording medium of specklegrams with carrying frequency fringes, to storage multiple interferograms, for uniform in-plane displacements, is presented. Experimental results are shown.
Optical Vortex Metrology from Phase Modulo 2 π Maps
Frontiers in Optics 2012/Laser Science XXVIII, 2012
ABSTRACT Conventional Optical Vortex Metrology techniques rely on the generation of pseudo-phase ... more ABSTRACT Conventional Optical Vortex Metrology techniques rely on the generation of pseudo-phase maps for image processing and measuring. In our work, as a novel alternative the application of this techniquefrom phase modulo 2π maps is discussed.
Optics Communications, 1998
The use of an electro-optic crystal as phase-stepping device in a digital speckle interferometer ... more The use of an electro-optic crystal as phase-stepping device in a digital speckle interferometer is discussed. Phase stepping is introduced by varying the external voltage applied to the crystal. The crystal calibration procedure is outlined and errors are discussed. Experimental results compared to those obtained with a piezo-electrically driven mirror are presented.
Advances in Optical Speckle Processing, Lecture II
SciVee, 2011
<title>Features of photorefractive registered speckles</title>
Selected Papers from International Conference on Optics and Optoelectronics '98, 1999
ABSTRACT
Image enhancement in multiplexed data by using phase gratings in theta modulation encrypting techniques
Frontiers in Optics 2012/Laser Science XXVIII, 2012
We present an improvement to the theta modulating techniques for multiplexing encrypted images. W... more We present an improvement to the theta modulating techniques for multiplexing encrypted images. We introduce sinusoidal phase gratings finding an increase in the contrasts of the decrypted images thanks to energy redistribution.
Multiplexing encryption technique by combining random amplitude and phase masks
Optik - International Journal for Light and Electron Optics, 2009
We propose and demonstrate an encryption-selectable undercover multiplexing. We encrypt and multi... more We propose and demonstrate an encryption-selectable undercover multiplexing. We encrypt and multiplex images for storage by means of a random phase mask common to every image, covered with random amplitude masks different for each image. In order to get a ...
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Papers by Néstor Bolognini