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.

Abstract: An array of acoustic transmit/receive transducers is placed near the body to be imaged. Acoustic energy is projected upon the body sequentially from different ones of the transducers, each projection covering the entire scene or field of view which it is desired to image. The electrical signals produced from reflected acoustic energy picked up by different transducers are phase shifted, or time delayed as appropriate, so that those from any particular point within the body will additively combine in amplitude, while signals from other points will not. In so doing, there is preserved not only the information about the amplitude of the combined signal from the transducers, but also any information about phase shifts (or time delays as the case may be) which does not result in complete alignment of the signals from the different transducers. The resulting complex signals are further processed, to vectorially add them.

Abstract: Certain ones of a total array of ultrasonic transducers constitute a small aperture and are so energized as to project acoustic energy onto predetermined parts of a scene. Reflections of the transmitted signals are received by certain ones of the array, are converted to electrical signals and are appropriately delayed to enable additive combination of the amplitude of the received signals emanating from the same points in the scene ("targets"). The phase (or time delay) as well as the amplitude information of the reflective signals are stored. Next, the same transmitting elements ("subarray") project acoustic energy upon the remaining parts of the scene in sequence and the reflected signals are similarly processed and stored. This continues until all the parts of the predetermined scene have been interrogated by insonification from that subarray and the reflected signals have been similarly processed.