This paper presents the beam tracing with refraction method, developed to examine the possibility of creating the beam tracing simulation of sound propagation in environments with piecewise non- homogenous media. The beam tracing with refraction method (BTR) is developed as an adaptive beam tracing method that simulates not only the reflection but also the refraction of sound. The scattering and the diffraction of sound are not simulated. The BTR employs 2D and 3D topology in order to efficiently simulate scenes containing non-convex media. After the beam tracing is done all beams are stored in a beam tree and kept in the computer memory. The level of sound intensity at the beginning of each beam is also memorized. This beam data structure enables fast recalculation of results for stationary source and geometry. The BTR was compared with two commercial ray tracing simulations, to check the speed of BTR algorithms. This comparison demonstrated that the BTR has a performance similar to state-of- the-art room-acoustics simulations. To check the ability to simulate refraction, the BTR was compared with a commercial Finite Elements Method (FEM) simulation. In this comparison the BTR simulated the focusing of the ultrasound with an acoustic lens, with good accuracy and excellent performance.
This paper presents a method of correcting the effects caused by refraction phenomena in an optical measurement system. The correction algorithm proposed can be applied in many different photogrammetric applications affected by these effects. To validate this algorithm, a foot sole optical measurement system that uses several cameras to build a mesh of a foot sole has been used. This measurement system has six cameras that are protected by a safety glass that separates the cameras from the foot to be measured. The safety glass produces an air-glass-air interface that causes the refraction phenomena, producing deformations in the images. Due to the deformations it is impossible to obtain reliable metric information of the images captured using the measurement system. The developed correction algorithm is based on a grid layout and associated polynomials and makes it possible to correct the deformations and extract accurate metric information.
Two highly sensitive optical sensor topologies are proposed and simulated in this paper. The proposed structures are optimized to provide better performance characteristics such as sensitivity, detection limit, and quality factor. They are based on two-dimensional photonic crystals consisting of rectangular arrays of GaAs rods in SiO2 substrates. Such lattices have bandgaps for transverse magnetic modes. Two-dimensional finite difference time domain and plane wave expansion methods are used for the simulation and analysis of the refractive index sensors and particle swarm optimization method is used to optimize the structural parameters. The designed structures show a high sensitivity to refractive index variations. They are able to detect refractive indices from 1.33 to 1.5. An excellent figure of merit equal to 737 RIU−1 is observed for the proposed structure and a significant improvement is observed compared to the structures reported in the literature.