Importance

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Abstract

A synthetic aperture ultrasonic imaging system for imaging a target with a resolution limited by a designated aperture. A phased array of nonuniformly spaced ultrasound transducers having an average inter-transducer spacing which is greater than a .lambda./2 Nyquist spacing for the transducers is used for imaging in a manner so as to either obtain a desired point spread function which is unattainable by a single image taken by the nonuniformly spaced transducers or to provide coarray equivalence to a phased array of transducers which are uniformly spaced at the .lambda./2 Nyquist spacing for the designated aperture. Coarray equivalence makes possible the technique of applying amplitude weightings to each of the nonuniformly spaced ultrasound transducers during transmit and receive modes and by forming a number of component images which when added together form a sum image substantially equivalent to a single image formed by a scan beam of the uniformly spaced transducers with the designated aperture. The complex values of the resulting component images are then added on a point by point basis, preserving phase, such that a point spread function of the sum image is substantially equivalent to the desired point spread function of the single image formed by the uniformly spaced transducers with the designated ape STATEMENT OF GOVERNMENT INTEREST This invention was made with government support under contract N00014-89-J-1538 awarded by the Department of the Navy. The government has certain rights in the invention.

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First Claim