16 March 2006 Breaking the resolution limit: an exciting experimental result
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Abstract
For more than a century the possibility of imaging the structure of a medium with diffracting wavefields has been limited by the tradeoff between resolution and imaging depth. While long wavelengths can penetrate deep into a medium, the resolution limit precludes the possibility of observing subwavelength structures. Recent progress in microscopy has shown that by exploiting the super-oscillatory properties of evanescent fields, resolution several orders of magnitude smaller than the wavelength can be achieved so leading to Near-field Scanning Optical Microscopy. Based on a similar argument, this paper investigates the possibility of obtaining super resolution in the far-field (here far-field refers to a distance greater than λ, which would enable high resolution imaging at relatively large depth. The theoretical principles which result in the resolution limit are reviewed and a new strategy to overcome it is proposed. An advanced imaging algorithm for linear and two-dimensional array probing systems is presented and its capability of resolving targets as close as λ/3 is demonstrated experimentally, the targets being at several wavelength distance from the array. The results show that the method is superior to conventional techniques such as Synthetic Aperture Focusing, Synthetic Phased Arrays and Time Reversal.
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Francesco Simonetti, "Breaking the resolution limit: an exciting experimental result", Proc. SPIE 6147, Medical Imaging 2006: Ultrasonic Imaging and Signal Processing, 61470E (16 March 2006); doi: 10.1117/12.666731; https://doi.org/10.1117/12.666731
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