1,720,967 research outputs found
Sistema optimizado para la captura de imágenes de fondo de ojo
Get PDFEstá comprobado que el uso de óptica adaptiva para la compensación de aberraciones
de ojos humanos in - vivo, mejora la resolución lateral de imágenes de fondo de ojo. Un
esquema de óptica adaptiva está compuesto básicamente por tres componentes; un dispositivo
de medición de aberraciones, un dispositivo de compensación de aberraciones y
un sistema de control que sincronice los dos primeros en un bucle de medición – compensación.
En éste trabajo de investigación se presenta un arreglo experimental para la
captura de imágenes in - vivo de fondo de ojo, en un esquema optimizado en tamaño y
número de lentes, tal que las aberraciones del sistema óptico de formación de imágenes
debido a las lentes se ve reducido. Éste sistema usa un sensor de frente de onda de tipo
Shack–Hartmann y un espejo deformable para su brazo de óptica adaptiva. Se presentan
resultados experimentales de medición de aberraciones y fondo de ojo utilizando un ojo
modelo y ojos in-vivo capturadas con el arreglo experimental implementado. La seguridad
de los ojos voluntarios se garantizó siguiendo la norma ANSI z136.1-2000 la cual
especifica la potencia máxima que se puede irradiar sobre ojos humanos in - vivo
Application of acousto-optical interactions in crystals to performing the spectrum analysis of radio-signals and shaping the multi-wave coupled states
Get PDFAcoustic waves were studied extensively in the 19th century; surface acoustic waves were first described by Lord Rayleigh in 1885 as they pertained to earthquakes [1]. The acousto-optical effect was first studied or predicted by Brillouin in 1922 [2]. Physically, this effect describes the interaction between light and sound waves. This interaction produces the diffraction of light from the medium which was first perturbed by an acoustic wave. Later, in 1932 Debye and Sears [3] and Lucas and Biquard [4] verified it experimentally when optical sources of sufficiently high coherence become available. Surprisingly, a large number of diffracted orders were observed, symmetrically spaced about the undiffracted beam. Brillouin proposed that this effect was due to rescattering of light from the acoustic beam, it was quantified until a theoretical treatment using Feynman diagrams was presented in 1980 by Korpel and Poon [5]. This established a rigorous physical description of the multiple scattering of plane waves; a similar concept had been employed in a mathematical formalism first presented in 1960 [6].
The presence of multiple diffracted orders was first explained in a classic series of papers by Raman and Nath in 1935-1936 [7], who modeled the sound column as a phase grating acting in transmission to give rise to many diffracted orders by interference. They also considered the problem of oblique and arbitrary angle of incidence of light on the acoustic beam. Debye and Sears [3], who also derived a criteria for single- and multiple-order diffraction phenomena (Debye-Sears ratio)
One-dimensional apodization of light beams by the optimized quasi-Gaussian profiles in potential application to lighting the acousto-optical cells with appreciable linear acoustic losses
Get PDFThe most significant problems of determining the dynamic range of new acousto-optical spectrometers and
processors for astrophysical applications are under discussion. In so doing, two factors governing the dynamic
range of these acousto-optical systems are chosen for the investigations. At first, the influence of the acoustic
attenuation along large-aperture acousto-optical cells on the desired levels of lobes in a focal plane of the
integrating lens as analyzed, and then potential capabilities of exploiting the incident light beam apodization
for increasing the dynamic range of those acousto-optical systems are considered theoretically and within
preliminary experiments
Shaping the dissipative collinear three-wave coupled states in a two-mode medium with a square-law nonlinearity and linear non-optical losses
Get PDFDissipative multi-pulse three-wave coupled states, appearing with collinear Bragg light scattering in a two-mode square-law nonlinear medium with linear non-optical losses, are revealed. Both the localization conditions and the spatio-temporal distributions of their optical components are studied theoretically in quasi-stationary and non-stationary regimes. Then, dissipative multi-pulse three-wave coupled states have been observed within the acousto-optical experiments in a calcium molybdate crystalline collinear cell. The obtained experimental results are in rather good agreement with the non-stationary theory developed
The existence of five-wave non-collinear acousto-optical weakly coupled states
Get PDFFive-wave Bragg solitary waves in the form of weakly coupled states, occurring within a four-order non-collinear scattering of light by acoustic waves in an optically anisotropic crystal, are identified and investigated. Generally, we study this phenomenon in an arbitrary regime with the phase, i.e. frequency-angular, mismatches, while, for simplicity’s sake, the exact conditions appearing of localization for multi-pulse coupled states is illustrated in a regime of the phase synchronism. The spatial-frequency distributions of the optical components inherent in these solitary waves are investigated theoretically, simulated numerically and observed experimentally in a tellurium dioxide crystal. Much attention is given to the analysis of contributions conditioned by the effect of optical activity in a tellurium dioxide crystal of chosen orientation. The performed analysis makes it possible to estimate the effective photo-elastic constants for both normal and anomalous processes of light scattering rather accurately and, in so doing, to match theoretical estimations for the efficiency of multi-order acousto-optical interaction with the experimental results obtained
Efficiency of a one-phonon Bragg anomalous light scattering in tellurium dioxide single crystal with variously polarized incident light of visible range
No full textShaping five-wave non-collinear weakly coupled acousto-optical states in a TeO 2 single crystal
No full textOptically pumped three-wave coupled states in a waveguide with a square-law nonlinearity and losses
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Collinear acousto-optical three-wave solitary states in a two-mode medium with a square-law nonlinearity and losses
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