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Frequency-dependent focal length of a plano-spherical convex subsonic index lens
- Source :
- Journal of the Korean Physical Society. 78:784-795
- Publication Year :
- 2021
- Publisher :
- Springer Science and Business Media LLC, 2021.
-
Abstract
- This study aims to investigate the frequency-dependent characteristics of the focal length of an acoustic lens made of a material with a frequency-dependent acoustic refractive index (ARI). For this purpose, an exchangeable plano-spherical convex subsonic index lens (PSCSIL) was fabricated using a polydimethylsiloxane (PDMS) material. The ARI of the lens material was evaluated via the tone-burst through-transmission method over the frequency range of 1–10 MHz. The frequency dependence of the focal length of the fabricated PSCSIL was evaluated through graphical analysis of the acoustic field scanned by a hydrophone as well as of that simulated using the finite element method. The measured ARI and focal length were observed to be dependent on frequency. The simulated and measured focal lengths of the PSCSIL exhibited a great discrepancy with their respective values predicted using the conventional focal length equation. This discrepancy was further studied using the ray-tracing method and is described in the discussion section. In conclusion, the spherical curvature of PSCSIL does not induce the convergence of rays to meet in a point. The ray tracing method does not take into account the phase complexity of the near-field region inside the lens. This causes the actual focal length to be shorter than the predicted one.
- Subjects :
- 010302 applied physics
Physics
Hydrophone
business.industry
Phase (waves)
General Physics and Astronomy
02 engineering and technology
021001 nanoscience & nanotechnology
Curvature
01 natural sciences
Finite element method
law.invention
Lens (optics)
Ray tracing (physics)
Optics
law
0103 physical sciences
Focal length
0210 nano-technology
business
Refractive index
Subjects
Details
- ISSN :
- 19768524 and 03744884
- Volume :
- 78
- Database :
- OpenAIRE
- Journal :
- Journal of the Korean Physical Society
- Accession number :
- edsair.doi...........f411b60e6539c4def8e3ffa9551a3624