Other

Wavefield Image, Inc.

Norman S Neidell

Douglas J Morgan

J Robert Fort

Phillip C Landmeier

Stephen T Ha

Ernest E Cook

Acquired signals representing samples of propagating wavefields are processed using space-time linked variable methods to form images having better definition and resolution than may be obtained by conventional methods. Frequencies accessed include those anticipated as well as some apparently beyond those deemed feasible according to Nyquist criteria as well as those present in the wavefield source. The signals and physical features may be obtained in tomography (medical CT scans), echo location (radar or sonar) or seismic imaging for example. Signals are processed maintaining interrelation of the linked variables of time and space, rather than following the conventionally accepted current techniques which treat the time and space variables independently. Definition and resolution of images are obtained beyond those normally considered possible with earlier techniques by understanding and correctly interpreting the information content of a sampled wavefield. Data acquisition speed can be greatly increased, while acquisition costs are also reduced since the methods described require less data and use such data as available more effectively.

Sampling and reconstruction of propagating wavefields

A transducer capable of generating a phase-encoded wavefield is described. The encoded phase is related to the angular co-ordinates of direction of transmission. By decoding the phase values of the received wavefield, a direction can be obtained. Therefore, in navigation applications this transmitter gives additional location information not available from a single received signal using traditional methods such as 'range-range' and 'hyperbolic' systems. In its simplest configuration, the new transducer comprises two transducers which can be individually controlled. In more complex constructions use of more than two transducers increases the controllability of the desired phase characteristics of the resulting wavefield. It has also been discovered that by using two different phase-encoded wavefields, direction finding of small reflectors can not only be accomplished, but small reflectors can be distinguished from large plane reflectors or else dispersive properties of the propagation medium can be characterized. The first wavefield takes the form of monotonic phase increments with direction as for example would be produced by the present invention, while the second wavefield simply reverses the sense of phase increments of the first. The second wavefield is easily obtained from a source that generates the first either by reprogramming the electronic driving signals for transducers or mechanically interchanging the components of the transducers.

Transducer to generate phase-encoded wavefields

An acoustical imaging system for producing high resolution medical images provides a method and apparatus for obtaining accurate velocity characterizations of samples within the human body, and for obtaining high resolution images of the samples by utilizing the velocity characterizations of the samples within the human body. The acoustical imaging system also provides a method and apparatus for efficient use of switching channels whereby for a transducer array having a plurality of transducer elements, a set of receiver channels which number less than the number of transducer elements in the array are assigned to a selected portion of the plurality of transducers in the array, wherein for any predetermined set of transducers symmetrically located about a selected transducer, the predetermined set equal in number to the number of receiver channels in the system, each receiver channel in the set of receiver channels is only assigned to one transducer in said predetermined sampling set.

Synthetic aperture ultrasound imaging system

This invention consists of producing a two-dimensional display from exploration seismic data designed to indicate zones of anomalous low velocity in the subsurface. Such zones may be indicative of porosity and the possible occurrence of hydrocarbons. They will be localized in terms of position along the seismic profile and in approximate zone of reflection arrival time. Data used in making the display are derived from both the CDP stacked seismic profile and corresponding velocity analyses used also to stack the data itself. Stacking velocity curves are plotted according to CDP location for each reflector designated by an interpreter to be of interest. These curves are overlain in pairs using calibration calculations and empirical criteria. Calibration helps smooth 'noisy' values and compensates for velocity variations resulting from changes in separation or dip of the two reflectors from which the overlain velocity curves derive. In addition, it is presumed that the interval bracketed by each reflector pair taken in turn has uniform or only regional lateral variations of interval velocity--no local lateral variation is assumed. 'Cross overs' or convergences of the paired curves thus indicate zones of either high or low interval velocity of local nature. The display itself consists of the velocity curves for all possible reflector pairs and vertical bands of color which are assigned to identify the reflection interval of particular low velocity zones which are shown consistently by all reflectors taken in pairs which bracket such zones. Horizontal position is of course indicated by the CDP location.

Seismic method for identifying low velocity subsurface zones

Navigation systems which position one or more mobile platforms in real time with appropriate accuracy in reference to a known system of coordinates by the emission of signals into a propagation medium and processing them after detection are disclosed. Broad-band, broad-beam signals are employed. All received signals convey phase encoded angular coordinate information which characterizes the particular signal path. Phase encoding of angular information is effected by suitably configured 'lenses' of dispersive materials or by post-critical angle reflection from a suitably configured reflector and shield combination. When the angular coordinate information is used in conjuction with range determinations from detected signals, an especially useful navigation system is provided which can operate from a single reference station.

Navigational systems using phase encoded angular coordinates

This invention generally relates to navigation systems which seek to position in real time with appropriate accuracy one or more mobile platforms in reference to a known system of coordinates by the emission of signals into a propagation medium and processing them after detection. Broad-band, broad-beam signals are employed. All received signals convey phase encoded angular coordinate information which characterizes the particular signal path. When the angular coordinate information is used in conjunction with range determinations from detected signals, an especially useful navigation system is provided which can operate using only a single reference station.

This invention generally relates to echo location or ranging systems in which the individual properties of targets or reflectors (such as range, bearing, elevation angle, relative velocity, impedance contrast, etc.) in a field of targets within some propagation medium are identified by the emission of signals into the propagation medium and processing of the detected reflections from the target field.

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Houston, TX, United States of America

Norman S Neidell