Diffractive optics, such as Phase Fresnel Lenses (PFL’s), offer the potential to achieve excellent imaging performance in the x-ray and gamma-ray photon regimes. In principle, the angular resolution obtained with these devices can be diffraction limited. Furthermore, improvements in signal sensitivity can be achieved as virtually the entire flux incident on a lens can be concentrated onto a sma...

Ultra high-resolution measurements of amplitude and phase fields emerging from fine period amplitude gratings are presented and discussed. In the axial direction periodically repeated features are found, whose origins are the Talbot effect within the Fresnel diffraction regime. The phase field recording leads to a very precise measurement of the localization of the Talbot planes and precisions ...

This paper describes the use of a building database and a three-dimensional formulation of the Fresnel-Kirchoff diffraction theory to compute the shadowing by buildings in the general situation where diffraction can occur by building edges of both horizontal and vertical orientation. The storage format of buildings in a geographi_c information systems database is described. An algorithm is pres...

We present a new approach to efficiently compute effects of sound occlusion and diffraction by obstacles in general virtual acoustic environments. Based on the Fresnel-Kirchoff approximation to diffraction, our method uses a 3D model of the environment and computer graphics hardware to evaluate diffraction effects between a sound source and a receiver position. No further hypothesis is needed o...

The Huygens-Fresnel diffraction integral has been formulated for incident Gaussian laser beams by using the Kirchhoff obliquity factor with the wave front instead of the aperture plane as the surface of integration. Accurate numerical-integration calculations were used to investigate the Fresnel field diffraction region for the much-studied case of a circular aperture. It is shown that the clas...

A general fast numerical algorithm for chirp transforms is developed by using two fast Fourier transforms and employing an analytical kernel. This new algorithm unifies the calculations of arbitrary real-order fractional Fourier transforms and Fresnel diffraction. Its computational complexity is better than a fast convolution method using Fourier transforms. Furthermore, one can freely choose t...

An ultra-small micro spectrometer with less than 1mm diameter was constructed using Fresnel diffraction. The fabricated spectrometer has a diameter of 750micrometers and a focal length of 2.4 mm at 533nm wavelength. The micro spectrometer was built with a simple negative zone plate that has an opaque center with an ecliptic shadow to remove the zero-order direct beam to the aperture slit. Unli...

Phase Fresnel lenses have the same imaging properties as zone plates, but with the possibility of concentrating all of the incident power into the primary focus, increasing the maximum theoretical efficiency from 11% to close to 100%. For X-rays, and in particular for gamma-rays, large, diffraction-limited phase Fresnel lenses can be made relatively easily. The focal length is very long for exa...