| Español | HOME |
INSTITUTIONAL
|
RESEARCH
|
ACTIVITIES
|
LINKS |
History
Fotorrefractive optical processing
Holography at ciop
The first holograms made in Argentina (even in SouthAmerica) were devised and produced in 1969 at Laboratorio de Espectroscopía Óptica y Láser (LEOL), Faculty of Science, National University of La Plata. Those holograms were done by Licenciate José Lunazzi under the guidance of Dr. Mario Garavaglia. The holograms of small size were of different types: Gabor, Leith and Upatnieks as well as other configurations conceived by both researchers. In 1970 the student Héctor Rabal and the Licenciates Lía Zerbino and José Calatroni joined the group.
It should be pointed out that further on the LEOL group constituted the Centro de Investigaciones Opticas (CIOp) in 1977.
The main holographic techniques just known in those early years were also reproduced at CIOp. For instance, image holography and holographic microscopy. Besides, some holographic experiences were included in undergraduate courses as laboratory work for students in the last year of the Physics Licenciate Career. Furthermore, in 1973, some projects were carried on concerning experimental arrangements with double exposure holographic interferometry and real time (“in-situ”) holography applied to deformation measurements.
Doctoral Thesis of Lía Zerbino and Héctor Rabal issued in 1978 included some development related with holographic features of Fabry Perot interferometer measurements.
In 1979 took place at CIOp the Fourier Optics Workshop under the agreement of CONICET and National Science Foundation, USA, with the participation of highly qualified researchers and lecturers as Joseph Goodman, James Wyant, CharlesVest, Christ Dainty, Silverio Almeida and Emmet Leith, one of the pioneering researcher on holography. From 1979, several Doctoral Thesis mainly devoted to holography (Enrique Sicre, Néstor Bolognini, Roberto Torroba, Nora Rodriguez ) were carried on. In 1981 German researchers, K. Wanders, H. Steinbischler and G. Schweiger dictated a practical and theoretical holography course that could be considered a preceding step to the “Láser y Óptica en Ingeniería” course.
Professor Maurice Francon from Paris IV University visited CIOp in 1982 and dictated two courses about the recent progress on holography and related techniques. The increasing appeal to holography projects was also encouraged by the visit of Professor Jean Charles Vienot of Besancon University who dictated a two months course on holography in 1983. Afterwards, Professor Vienot visited CIOp several times, keeping up a continuous up-to-date on the subject.
This maintained interest renders good results. In 1986, a new arragement concerning rainbow holography was developed by CIOp researchers. Three years later, in was published a contribution were it was stated that some natural phenomena exhibited an holographic behaviour.
At that time, the public interest in holography prompted to spread out the basic principles and practical approaches on the subject. Therefore, a First Introductory Holography Course that includes a basic theory and practical demonstrations devoted to an audience without a scientific background was conducted at CIOp in June 1989. The course was supported by Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CICBA). Success in people attendance causes to repeat the course twice that year.
During 1990 and 1991 cooperative activities between artists and CIOp researchers leaded to some interesting developments in display holography.
In 1992, professional holographers Ken Harris and Kevin Brown in cooperation with Ricardo Arizaga, Héctor Rabal and Néstor Bolognini made holographic versions of Marta Minujin’s sculpture pieces in a rainbow type format.
It should be pointed out that in 1999, H. Rabal and R. Arizaga made a hologram that was developed with black coffee. It seems to be the first time this chemical procedure was employed.
By going back to 1991, “light in flight” experiments and contouring holography with low coherent sources were implemented. Also that year, digital holographic interferometry started at CIOp and a permanent interest remains in this field.
At present, holography is a main subject in different research lines, for example, dynamic holography in volume media.
Los holografistas profesionales Ken Harris y Kevin Brown en el año 1992 en cooperación con N. Bolognini, R. Arizaga y H. Rabal participaron en la realización de algunos hologramas H2 y arco iris de esculturas de Marta Minujin.
Digital-speckle processing
The beginning of this research line at CIOp traces back to the first papers we developed in metrology by means of speckle patterns. Speckle is the characteristic optical granularity arising when highly spatial coherent light illuminates any rough surface. The advent of the digital processing in the optical domain brought new possibilities, as the software manipulation of the speckle patterns. Digital correlation of speckle patterns results in fringes with the same interpretation as those obtained by classical holographic interferometry. A straightforward advantage is the fringe computer processing, where phase maps were automatically generated, saving time an efforts. Digital Speckle Pattern Interferometry (DSPI) became a new practical tool in optical metrology, generating some collateral research lines. In this frame, digital holography, Virtual Optical Imaging Systems, and more recently opto-digital encryption and validation profited from digital speckle advances. Our group actively contributed to this field developing application, including: digital holographic contouring, control and analysis of digital fringe visibility, optical fibers core measurements, speckle patterns temporal evolution, digital polarization encoding, digital techniques for high precision measurements of focal lengths, digital moiré techniques and its applications to metrology, digital encryption and validation.
Fotorrefractive optical processing
Photorrefractive effect takes place when a refractive index change is produced in a material due to non uniform light distribution. This effect is observed in electro-optic and photoconductive materials having donor and trap centers. The main advantage of photorefractives consist in producing non linear phenomena under low intensity levels (mW/cm2, mW/cm2).
Photorefractives are able to register dynamic holograms in terms of index gratings and to retrieve storage information in parallel, in real time and with a high fidelity. These materials are adequate for image processing due to their high sensitivity, reversibility, multiplexing, phase conjugation and optical amplification capabilities. In particular, it is employed in dynamic holography and reversible optical memories.
>Photorefractive image processing research starts at CIOp in 1987 being the first laboratory in our country to initiate this line of research. The photorefractive crystals have been utilized in image processing and optical metrology (novelty filter, dynamic optical correlation, image enhancement, Talbot and Lau interferometry, holographic memories, speckle metrology and encryptation). In photorefractive speckle metrology has been taking advantage from the photorefractive crystal volume features and three-dimensional nature of speckle in very innovative research.
Modulated speckle
The use of speckles for metrological application has generated a great interest at CIOp since the early 80´s. In particular, the internal modulation of the speckle achieved by locating a multiple aperture pupil mask in front of the imaging lens allows the implementation of several metrological methods. At CIOp the specklegram obtained through an optical system whose pupil consists of multiple apertures in which the pupil change between exposures were widely studied. Applications were developed demonstrating the possibility of carrying out a variety of experiments which can not implemented otherwise. For instance, some developments include image multiplexing, speckle photography (to measure in plane displacements and rotation) and speckle interferometry (to characterize phase objects).
Since 90's at CIOp the use of photorefractive crystals as recording medium allowed implementing speckle metrology techniques in-quasi-real time and in-situ.