Abstract: A wavefront compensation technique which approaches the performance of Inverse Filtering while demonstrating adequate stability and signal to noise ratio. The spectrum amplitude is compressed in combination with phase deaberration algorithms by compressing the amplitude distortion using an amplitude compression function, such as an Mth root function, which converges the amplitudes towards the ideal inverse filtering solution in conjunction with conventional phase deaberration algorithms. Wavefront compensation using the compressed amplitude distortion data in accordance with the invention provides substantial contrast improvement over conventional phase only deaberration algorithms. In experiments, the mainlobe diffraction shape has been restored down to a -30 dB level necessary for resolving small breast lesions.

Abstract: A technique for subspeckle visibility in ultrasound imaging by using the speckle signatures to differentiate soft tissue from dense tissue and solid or compact objects. The information provided by a disparity mapper is used to automatically mark or tag these objects based on the observation that slight natural motion in soft tissue, as caused by breathing or probe compression, changes the details of a speckle pattern. This results from differential displacements among scatterers which alter the phase relations between their scattered fields. A small, compact object is displaced and distorted less, implying that its reflectivity pattern should be relatively stable, as compared to the fluctuating background reflectivity. This difference in the way the speckle patterns respond to body motion is detected by the disparity mapper. The output of the disparity mapper serves a marker or tag of dense tissue such as tumors or compact objects such as bits of shrapnel.

Abstract: An ultrasound or electromagnetic imaging system characterized by a two-dimensional phased array of ultrawideband, ultrasparse transducers. Ultrasparse is defined as an average inter-transducer spacing' which is greater than a .lambda./2 Nyquist spacing for the transducers and which is greater than a pulse length cT, where c is the speed of propagation of a pulse from a transducer in the imaging medium and T is a duration of the pulse. An ultrawideband low Q transient pulse is emitted by each of the transducers during a transmit mode, and the resulting ultrasound image signals are received from the transducers during a receive mode, processed, and displayed. Preferably, the transducers are uniformly weighted and excited and periodically spaced by distance and/or angle within the coordinate system of the two-dimensional phased array such that projections of the transducers onto a coordinate axis of the coordinate system minimally overlap.

Abstract: A method of high resolution imaging and identifying of targets with an Inverse Synthetic Aperture RADAR (ISAR) coupled with Adaptive Beam Forming (ABF) is disclosed. The ISAR system utilizes a pulsed RADAR transmitter and a highly thinned, dispersed phased array with random, non-colinear elements. An adaptive processor and feedback loop performs the ABF process such that high resolution of a moving target is possible. The high resolution signal allows accurate imaging and identification of the moving target.

Abstract: An array of acoustic receiving transducers is placed next to the body to be imaged. Acoustic energy is initially projected through the body, picked up by these receiving transducers, and processed to determine any time domain deviations which exist in the paths actually followed by that energy from those paths which would have been followed if the body were substantially homogeneous and the transducer array substantially fixed. Further acoustic energy is also picked-up by the transducers, after reflection within the body to be imaged. The image of any given point within the body is then formed by selecting from each transducer output signal that portion which corresponds to the image forming energy emanating from that point, as corrected in accordance with the previously determined deviations.

Abstract: 1. In a secure communication system; means for producing an analog intelligence signal; means for limiting the amplitude of said signal; means for transforming portions of said amplitude limited signal occurring in time sequence into a corresponding digital signal consisting of sequentially occurring n-digit words; means for combining said digital signal with a digital keystream signal in modulo 2.sup.n fashion; and means for transforming the digital signal produced by said combining means into an analog signal.