By using the Generalized Lorentz-Mie Theory (GLMT), which was successfully adapted from optics to acoustics, we present a thorough parametric study of acoustic forces in a standing-wave levitation trap, which allows us to identify the most relevant parameters of the levitation devices, while exploring the size ranges of the objects that can be acoustically levitated in these kinds of traps. We show that particles can be trapped either in pressure nodes or antinodes, depending solely on their size. This is analogous to the particle size-effect found in optical traps with complex light potentials. We present theoretical and experimental results for airborne levitation that are in excellent agreement.
A configuration for the measurement of thickness changes in materials through one-shot digital speckle pattern interferometry (DSPI) was developed. The phase maps calculation was made by adding carrier fringes by the multiple aperture principle and Fourier Transform Method (FTM). With this setup, interferometry configurations verified that the simultaneous and instantaneous visualization of two opposite faces of a surface is possible. In addition, the combination of the simultaneous results obtained from both sides of the material makes it possible to determine displacements with greater sensitivity or to identify changes in their thickness. The validation and demonstrative tests were carried out with a 1-mm thick aluminum plate with a 5-mm diameter through hole coated. Thickness changes until 2 μm was measured.
A configuration for the measurement of thickness changes in materials through one-shot digital speckle pattern interferometry (DSPI) was developed. The phase maps calculation was made by adding carrier fringes by the multiple aperture principle and Fourier Transform Method (FTM). With this setup, interferometry configurations verified that the simultaneous and instantaneous visualization of two opposite faces of a surface is possible. In addition, the combination of the simultaneous results obtained from both sides of the material makes it possible to determine displacements with greater sensitivity or to identify changes in their thickness. The validation and demonstrative tests were carried out with a 1-mm-thick aluminum plate with a 5-mm diameter through hole coated. Thickness changes to 2 μm were measured.
We present a powerful and efficient technique to structure acoustic fields, based on the use of active diffraction elements, which can be designed in practically arbitrary shapes and can be operated within a broad spectral range of ultrasonic frequencies in air. Two kinds of structured fields are demonstrated: focused acoustic vortices and the simultaneous generation of multiple acoustic Bessel beams of different topological charges, well separated among each other along the propagation axis. In both cases, the main parameters of the field can be finely and continuously tuned by setting the operation frequency. Experimental results show very good agreement with theoretical analysis and numerical simulations.
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