ACOUSTICAL LENS Russian patent published in 2017 - IPC B06B3/04 

FIELD: physics.

SUBSTANCE: acoustic lens is made in the form of a cuboid with a radial gradient of the acoustic refractive index with the cuboid edge value equal to (0.9-1.2)λN, where N=1,2, …, λ - the length of the elastic wave. The acoustic lens has a relative acoustic refractive index value of 1.1 n_env to 1.6n_env, where n_env - the acoustic refractive index of the lens environment, and a sound-permeable channel of constant cross-section is made along the optical lens axis with a characteristic transverse dimension of not more than 0.25λ, filled with a material with an acoustic refractive index, equal to n_cp.

EFFECT: providing an elastic wave focus to the area of a width less than the diffraction limit.

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