Abstract: Method and apparatus for ultrasonically imaging objects of interest. The apparatus includes an elongate source of coherent acoustic waves which are brought to a line focus and propagated in an object of interest. The acoustic waves are detected by an elongate linear array of substantially point receivers which are located parallel to the elongate source and substantially at the line focus. The elongate source and the linear receiver array are translated together relative to the object of interest so that an area is swept out across the object of interest. The amplitude and the phase of the acoustic waves scattered by the object of interest are detected by the receiver array, digitized and back wave reconstructed to yield a digital image of the object of interest.

Abstract: An apparatus for ultrasonically measuring concentrations of stress in objects of interest. The apparatus includes an ultrasonic transducer array for propagating acoustic waves in an object of interest along a plurality of determinable directions and from a plurality of determinable positions. A time interval counter measures the time of flight of the acoustic waves along the determinable directions and from the determinable positions. The time of flight measurements are reconstructed into a map of the variations in acoustic velocity within the object. The changes in acoustic velocity are then mathematically converted into a map of stress concentration areas in the object of interest.

Abstract: Method and apparatus for energizing an array of acoustic transducer elements to eliminate grating lobes. The apparatus includes a first subarray of N transducer elements arranged along an axis. The apparatus also includes a second subarray of N+1 transducer elements arranged along a second axis parallel to the first axis. One subarray is energized to propagate an acoustic beam having odd grating lobes with positive amplitude and the other subarray is energized to propagate an acoustic beam having odd grating lobes with negative amplitude. The two subarrays are disposed so that the radiated acoustic beams combine together and the odd grating lobes cancel each other.

Abstract: A linear transducer array for transmitting and receiving acoustic waves in both pulse-echo and holographic modes of operation. For pulse-echo acoustic imaging the array includes a linear subarray of transmitting transducer elements disposed in a plane along a longitudinal axis. Each transmitting element has an elongate shape and a principal axis that is perpendicular to the longitudinal axis of the array. For holographic imaging the apparatus further includes a removable mechanical shutter for blocking a predetermined portion of the principal axis of each of the transmitting elements so that a dispersive acoustic beam can be generated. The array also includes a linear subarray of receiving transducer elements coplanar with the transmitting subarray and disposed parallel to the longitudinal axis. The subarray of receiving elements is used to detect the reflected acoustic waves for both holographic and pulse-echo imaging.