Applied Physics

A Sharper Focus

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Science  18 Feb 2011:
Vol. 331, Issue 6019, pp. 823
DOI: 10.1126/science.331.6019.823-b

Imaging techniques are rarely applied in ideal environments. Ultrasound imaging, for instance, is hindered by scattering from tissue, bone, and other surrounding organs, which often blur the images. The same is true for terahertz body scanners, wherein scattering from clothing or designed concealers may obscure detection. Scattering from random scatterers creates speckle noise in the backscattered signal that results in an overall deterioration in image quality. Montaldo et al. show that this speckle noise can be controlled and mitigated by a time-reversed scattering process using a time-domain array of transmitters and receivers. By sending in pulses of ultrasound from the array and tweaking the timing at each array element, the signals at the receivers are fed back to the transmitters, and the timing is iteratively adjusted to effectively steer the pulses to focus on a desired point. The improved imaging capability is demonstrated in a phantom for ultrasound but should be extendable to other frequency regimes for radar and communication applications.

Phys. Rev. Lett. 106, 54301 (2011).

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