1 February 1993 Finite element area and line integral transforms for generalization of aperture function and geometry in Kirchhoff scalar diffraction theory
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Abstract
Two finite element-based methods for calculating Fresnel region and near-field region intensities resulting from diffraction of light by two-dimensional apertures are presented. The first is derived using the Kirchhoff area diffraction integral and the second is derived using a displaced vector potential to achieve a line integral transformation. The specific form of each ofthese formulations is presented for incident spherical waves and for Gaussian laser beams. The geometry of the twodimensional diffracting aperture(s) is based on biquadratic isoparametric elements, which are used to define apertures of complex geometry. These elements are also used to build complex amplitude and phase functions across the aperture(s), which may be of continuous or discontinuous form. The finite element transform integrals are accurately and efficiently integrated numerically using Gaussian quadrature. The power of these methods is illustrated in several examples which include secondary obstructions, secondary spider supports, multiple mirror arrays, synthetic aperture arrays, apertures covered by screens, apodization, phase plates, and off-axis apertures. Typically, the finite element line integral transform results in significant gains in computational efficiency over the finite element Kirchhoff transform method, but is also subject to some loss in generality.
Hal G. Kraus, "Finite element area and line integral transforms for generalization of aperture function and geometry in Kirchhoff scalar diffraction theory," Optical Engineering 32(2), (1 February 1993). https://doi.org/10.1117/12.60856 . Submission:
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