Abstract
The improvement in focusing capabilities of a set of annular scatterers arranged in a fractal geometry is theoretically quantified in this work by means of the finite element method (FEM). Two different arrangements of rigid rings in water are used in the analysis. Thus, both a Fresnel ultrasonic lens and an arrangement of rigid rings based on Cantor prefractals are analyzed. Results show that the focusing capacity of the modified fractal lens is better than the Fresnel lens. This new lens is believed to have potential applications for ultrasonic imaging and medical ultrasound fields.
Highlights
It has been found that certain natural phenomena, such as snowflakes or the structure of leaves in certain plants, display self-similar patterns
FRZPand andthe the Figure shows the spatial distribution of the sound pressure level of the modified lens in the in both lenses some focal zones can be considered, it is worth
The ultrasonic modified fractal zone plate (FRZP) lens is here proposed as an alternative to the Fresnel zone plates (FZPs)
Summary
It has been found that certain natural phenomena, such as snowflakes or the structure of leaves in certain plants, display self-similar patterns These distinctive features can be associated with the fractal concept. Sapoval et al [4] investigated numerically the acoustical properties of irregular cavities described by fractal shapes. They showed that the geometrical irregularity enhanced the low frequency modal density and localized many of the modes at the cavity boundaries, and that the damping characteristics of the cavity were modified. Targeting of ultrasonic beams of MHz order are essential for noninvasive tissue ablation Based on these studies, a new possibility of constructing lenses different from the most common cases that are constructed by refractive materials with curved surfaces is proposed. Fresnel lenses have been investigated [10,11], and both air and water, acoustic Fresnel lenses have been investigated [10,11], and labyrinthine channels labyrinthine have recentlylenses been to used in Fresnel to increase have recentlychannels been used in Fresnel increase their lenses efficiency [12,13]. their efficiency [12,13]
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