arXiv subjects

J. B. Almeida

Publications and source records attributed to J. B. Almeida.

4 recordsLinked to original sources

arXiv2004

Corneal thickness and elevation maps computed from optical rotary scans

Purpose: Recently the authors presented a technique that allows corneal thickness measurements along any meridian from optical sections obtained using a rotary scanning system. This paper presents 3-D mapping of the corneal thickness and topography of both corneal surfaces, obtained with the rotary system. Method: Corneal thickness and topography are computed from optical sections obtained by illumination with a collimated beam expanded in a fan by a small cylindrical lens. This lens is provided with motor driven rotation in order to perform automated rotary scan of the whole cornea. Two cameras are used to capture the images of the optical sections. Results: With this system it is possible to obtain 3-D representation of the corneal thickness as well as corneal topography. Corneal thickness and elevation maps are shown. Conclusions: Although still under development, this new optical system allows the measurement of the thickness of the whole cornea as well as 3-D mapping of both corneal surfaces.

physics.gen-ph↗

arXiv2003

Wide angle near-field diffraction and Wigner distribution

Free-space propagation can be described as a shearing of the Wigner distribution function in the spatial coordinate; this shearing is linear in paraxial approximation but assumes a more complex shape for wide-angle propagation. Integration in the frequency domain allows the determination of near-field diffraction, leading to the well known Fresnel diffraction when small angles are considered and allowing exact prediction of wide-angle diffraction. The authors use this technique to demonstrate evanescent wave formation and diffraction elimination for very small apertures.

physics.optics↗

arXiv2003

Wigner distribution transformations in high-order systems

By combining the definition of the Wigner distribution function (WDF) and the matrix method of optical system modeling, we can evaluate the transformation of the former in centered systems with great complexity. The effect of stops and lens diameter are also considered and are shown to be responsible for non-linear clipping of the resulting WDF in the case of coherent illumination and non-linear modulation of the WDF when the illumination is incoherent. As an example, the study of a single lens imaging systems illustrates the applicability of the method.

physics.optics↗

arXiv2000

Optical interpretation of special relativity and quantum mechanics

The present work shows that through a suitable change of variables relativistic dynamics can be mapped to light propagation in a non-homogeneous medium. A particle's trajectory through the modified space-time is thus formally equivalent to a light ray and can be derived from a mechanical equivalent of Fermat's principle. The similarities between light propagation and mechanics are then extended to quantum mechanics, showing that relativistic quantum mechanics can be derived from a wave equation in modified space-time. Non-relativistic results, such as de Broglie's wavelength, Schroedinger equation and uncertainty principle are shown to be direct consequences of the theory and it is argued that relativistic conclusions are also possible.

physics.optics↗