Abstract: In accordance with the principles of the present invention, advantage is taken by the inventors of the fact that the speed of operation of the digital hardware in a digital beamformer having a plurality of parallel receiving channels can be reduced by providing multiple phases for the data signals supplied by each receiving channel and then processing the multi-phase data in N parallel summing paths. An interpolation-decimation filter receives the multi-phase data from the N parallel summing paths and provides at its output a signal having a reduced data rate (1/N). In accordance with this technique, the speed of operation of the individual digital circuits for forming the required beamforming delays are not increased as compared to conventional post-beamforming interpolation schemes, so that hereby the effective data rate is increased by a factor N and the delay quantization error is reduced by a factor N.

Abstract: The acoustic lens system is used for ultrasonic imaging in an ultrasonic system which displays an image of an object while transmitting ultrasonic waves and receiving the ultrasonic waves reflected from the object, and has a half field angle .omega. expressed as follows: ##EQU1## wherein the reference symbol v.sub.0 represents the velocity of sound in the medium located on the incidence side of the first lens surface and the reference symbol v.sub.1 designates the velocity of sound in the medium located on the emergence side of the first lens surface. Accordingly, the acoustic lens system according to the present invention is remarkably excellent in the performance thereof in respect of field angles, aberrations, aperture angles, attenuation, etc., and has an advantage to permits further reducing acoustic attenuation and preventing spurious images from being formed due to multiple reflections by arranging antireflection films on the lens surfaces.

Abstract: A delay interpolator for use in each channel of a digital ultrasound beamformer includes an FIR digital filter that is responsive to delay control information for delaying digital samples of the received beam by different delays that are quantized in increments less than the sampling period and a control unit for supplying the delay control information to the FIR digital filter. In a preferred embodiment, all but one of the filter coefficients are of the form 1/2.sup.m, where m is an integer, and multiplication is implemented in the FIR digital filter by shifting bits of the data samples by m bit positions. The FIR digital filter preferably includes a gain correction multiplier for correcting the gain of the delayed digital samples. The FIR digital filter delay interpolator can utilize a pipeline structure for high speed operation. In addition, the FIR digital filter delay interpolator can be used in a time multiplexed beamformer to process several beams simultaneously.

Abstract: A signal processor eliminates sidelobe response from signals produced by a spaced antenna array that forms a single beam using spatial frequencies. The signal processor also produces error signals. The signal processor uses a phase coherent local oscillator to simultaneously convert the wavefront signal from each element of the antenna array to three different first intermediate frequency signals IF. The first IF signals of each element are cross-correlated with the first IF signals from each of the other array elements to form the signals containing sampled spatial frequency components IF.sub.2. Cross-correlating a second time using the sampled spatial frequencies as inputs produces signals containing derived spatial frequency components IF.sub.3. The signals containing derived spatial frequency components are synchronously detected (phase compared) and summed to provide a single beam output signal.

Abstract: A wideband, derivative-matched, continuous aperture acoustic transducer includes a first sensor area having a predetermined spatial shading and a second sensor area having a spatial shading which is the spatial derivative of the spatial shading of the first area; the first and second spatial shaded areas are superimposed and co-extensive along the sensing axis.

Abstract: An array of transducer elements receives energy from a target or targets in a field of view and operates on the transducer outputs to provide a plurality of different levels of shading. The most useful portion of the field pattern is selected and combined with other most useful portions of other field patterns into a single composite display which results in one or more relatively narrow lobes, indicating targets, and without the presentation of side lobes which may be masking targets.

Abstract: A sonar system wherein sum and difference beam patterns are generated utilizing a plurality of transducer elements arranged in a line array. Receiver apparatus including a receiver transducer also constituted as a line array perpendicular to the transmitter transducer is used to form sum and difference receiver beams and return signals are processed so as to accurately define the azimuth as well as elevational position of a target within a target area.

Abstract: An apparatus for the examination of an object by ultrasonic echography, includes an array of n ultrasonic transducers which is associated with a stage for the emission of signals for scanning the object and with a stage for receiving and processing echographic signals retumed to the transducers, by the obstacles encountered in the object scanned. The emission stage is configured for the focusing of m simultaneously emitted ultrasonic beams, by virute of n emission modules, each of which, for example, the i.sup.th emission module, itself contains m signal generators (201a.sub.1, . . . , 201m.sub.1) which are connected in parallel (or a single signal generator followed by m parallel-connected delay circuits), a stage (202i) for combining the m signals thus generated, and an amplifier (203i) for applying the amplified combined signal to the transducer (10i) corresponding to the relevant emission module.

Abstract: A beamformer system is disclosed which includes an array of sensors such as ydrophones which produce signals from which information relating to a target is to be determined. The beamformer system includes a channel for each sensor, the channel including a varable length shift register which provides bulk delay to received signals, a FIR interpolation filter which provides vernier delay and shading. The system also includes a summation tree which adds the received signals and a sign extension/bit reversal filter to avoid authmetic overflow.

Abstract: A beam former for a ultrasonic diagnostic apparatus is arranged to have low-bit analog-to-digital converters and enables to obtain an excellent echo signal from blood flow. The beam former further includes a sample and hold circuit for sampling an echo signal of a pulse reflected from the inside of a human body. A delaying circuit serves to delay the output of the sample and hold circuit by a delay time corresponding to an integer multiple of a transmitted pulse period and is subtracted from the output of the sample and hold circuit. The subtracted output is analog-to-digital converted and is stored in a memory. The memory reads out the data asynchronously with the storage. The delaying circuit is composed of an analog-to-digital converter, a memory and a digital-to-analog converter and has a delay time corresponding to an integer multiple of the transmitted pulse period.

Abstract: Apparatus and method for compensating for differences in time at which an incoming acoustic wave is received by an array of acoustic signal receivers to take account of the shape of the incoming wave and the non-zero incidence angle of its approach. Each receiver is provided with a time delay module that introduces a large or coarse scale time delay .DELTA.t.sub.L plus a small or fine scale time delay .DELTA.t.sub.S, where .DELTA.t.sub.L is an integral multiple of a coarse scale time interval length .DELTA.t.sub.c and .DELTA.t.sub.S may be varied continuously from 0 to a predetermined time interval length (.DELTA.t.sub.S).sub.max that may be made at least as large as .DELTA.t.sub.c.

Abstract: A device is provided for processing an echo received by an array of N receiving elements from a target at range R ensonified by an LFM signal of bandwidth B transmitted for a duration T. The device receives each elements output f.sub.n (t) over the elements total receiving time and selects time window element outputs f'.sub.n (t), which are discrete portions of f.sub.n (t), each time window extending from an arbitrary initial time T.sub.0 to time T.sub.f and is spaced from T.sub.0 no more than T and, if there is a target within the window, an echo is received at time T.sub.n. Further the device produces element frequency difference outputs g.sub.n (t) from the frequency difference between a replica of at least a portion of the transmitted LFM signal and the time window element outputs f'.sub.n (t), the outputs g.sub.n (t) being tones with frequencies directly proportional to the time T.sub.n of the target from the time T.sub.0 so that the target range R=(c/2)(T.sub.0 +T.sub.n)+.DELTA.R.sub.

Abstract: A wideband, derivative-matched, continuous aperture acoustic transducer includes a first sensor area having a predetermined spatial shading and a second sensor area having a spatial shading which is the spatial derivative of the spatial shading of the first area; the first and second spatial shaded areas are superimposed and co-extensive along the sensing axis.

Abstract: An array of receiver elements in a radar or sonar system is synthetically elongated resulting in a narrower beam pattern. This is accomplished by sampling each output signal of the receiver elements, converting the signal to I and Q components for determination of a magnitude and phase angle. The phase angle is modified by a certain phase modulation factor f.sub.m and new I and Q components are calculated using the modified phase angle. The modified I and Q components from all of the received elements are combined for display purposes.

Abstract: An ultrasonic wave beam former including: a ultrasonic wave probe (1) equipped with a plurality of transducers (2) for converting a ultrasonic wave signal to an electric signal for effecting a dynamic focus by multiplying each channel signal as an output signal from each of the transducers (2) by a reference wave signal having the phase which is dynamically adjusted for each channel, and adding together each after-multiplication signal after the multiplication through a delay line (3), characterized in that at least two kinds of reference signals having mutually different frequencies are provided for each of the channels and at least two multipliers (10) are also provided;each of the reference signals is constituted so as to receive an ultrasonic wave signal from a direction differenct from others and have a phase angle (.theta.

Abstract: A PASS ultrasonic system performs a scan in which phase errors due to aberrations in the sound media are corrected prior to the acquisition of each beam. Phase errors are measured by cross correlating each of a set of reference beams with the desired beam to produce beam forming errors as a function of beam angle. This function is Fourier transformed to produce phase corrections that are employed by the ultrasonic system to offset the phase errors.

Abstract: An array for receiving wave energy at a pair of widely spaced frequencies has receiving elements arranged to function as a half-wave array for the lower frequency and as a random array for the higher frequency. A plurality of receiving elements are arranged in an array with the receiving elements having nominal positions spaced apart such that spacing between adjacent nominal positions is approximately one half the wavelength .lambda. of the wave having the lower frequency. The receiving elements are randomly distributed about their respective nominal positions with each receiving element being within a distance of .epsilon..lambda..sub.o of its corresponding nominal position where .epsilon. is a randomization parameter and .lambda..sub.o is the wavelength of the higher frequency wave.

Abstract: A Frequency Dispersive Transmitting Array (30) for propagating composite e energy (10) emulates narrow-band beams (20) of different frequencies which can be simultaneously radiated in all directions, or in any subset of directions, relative to an array (42) of radiating elements (32) because of the addition and cancellation of components of wave energy (10) radiated, is disclosed. A signal source (34) provides input signals (36), having frequencies which may be acoustic or electromagnetic, which are coupled by feedline (37) to radiating elements (32) through a plurality of time delay devices (38). Each one of time delay devices (38) is interposed between successive ones of radiating elements (32) and delays emission of replicas of signals (36) therefrom by a time delay .tau..sub.0 which is a multiple of the period of the dominant frequency radiated in a direction broadside to the array.

Abstract: Disclosed is a sonar for avoiding sub-surface underwater objects, for a surface vessel, having its directivity in elevation optimized to observe the surface and its surface reverberation reduced to the minimum. It consists in using an acoustic antenna having two columns of n transducers, the first column insonifying, at transmission, an elevation sector corresponding to the collision-risk zone and forming channels at reception, in the insonified elevation sector, the width of the channels being all the finer as the desired precision of the measurement of the position in elevation is high. The second column is necessary for the localization in relative bearing. The disclosure can be applied to the precise localization in elevation of objects located in the path of a vessel.

Abstract: An ultrasound apparatus has a first group of transmission and reception channels that are respectively allocated to elementary transducer in the active aperture of a connectable transducer array. The central transmission location generated by a transmission channel and the reception location sampled by a reception channel coincide and lie on the allocated elementary transducer. In addition, a second group of transmission and/or reception channels is present, each being respectively simultaneously connectable to a plurality of elementary transducers via transmission and/or reception transfer stages for generating a virtual transmission and/or reception location that lies between the elementary transducers.

Abstract: A phased array acoustic transducer apparatus has a controller and an array of ultrasonic transducers mounted in a water tight housing. Also included in the water tight housing are a transmitter circuit which sends phased excitation signals to the array of ultrasonic transducers so as to generate a directed beam of acoustic energy. A receiver circuit, located in the water tight housing, processes and combines signals received by the array of ultrasonic transducers to generate an output signal. The controller sends both power and control signals via a cable to the transmitter and receiver circuits. The cable uses a simple serial data line and a clock signal line to transmit beam angle control signals, thereby minimizing the size of the cable. The controller sends transmitter gating signals over a gate signal line on the cable to enable and disable operation of the transmitter circuit, such as is required for a pulse-echo mode of operation.

Abstract: A sonar that enables an already localized object to be found again uses a transmission antenna fitted out to transmit only the two .+-.first order secondary lobes. This antenna is supplied with a set of frequencies tiered so that each of these lobes determines a series of channels at transmission corresponding to these frequencies and filling two sub-sectors located to the right and to the left of the antenna. The reception is done by forming two wide channels, each of which covers one of the two transmission sub-sectors. The discrimination in bearing at reception is done by the discrimination of the frequencies. To cover a more extensive sector, including especially the central part located between two sub-sectors, the antenna can be made to rotate mechanically. This enables the construction of a simplified sonar which can be used in a consumable way.

Abstract: A system for reducing sidelobes of phased array antenna systems is performed by tapering the current amplitide of edge elements in the array while maintaining a full uniform current to the center elements in the array. Tapering may be adjusted with variable impedance devices until optimum sidelobe reduction is achieved.

Abstract: A method for imaging a sample with a beam of vibratory energy from an array of transducers excites the array with successive ones of a plurality M of coded excitation signal sets with each set occurring in a different one of successive excitation time intervals. Each different set has signals with a different code. An excitation beam, produced by the array, is focused into the sample at successively smaller distances, along a selected ray path from the array, during each successive excitation time interval. A reception beam is focused along the ray path at successively greater distances from a minimum distance away from the array during each successive one of a like plurality of reception time intervals, for receiving, during each reception time interval, return response signals reflected from the sample.

Abstract: An ultrasound system for investigating a subject comprises a probe, a signal processing module, and an interconnecting cable. The probe includes an annular phased array transducer defining multiple signal processing channels. The signal processing module includes a controller, a transmitter, a receiver, delay circuitry, and a video section. Within the delay circuitry, each signal processing channel includes an inphase branch and a quadrature branch. Each branch includes an analog-to digital converter (ADC) and a delay first-in-first-out (FIFO) memory. Dynamically variable delays are implemented by varying the sampling and FIFO input rates relative to constant FIFO output rates. The variable clock rates are derived by switching between phase-staggered replicas of a master clock MCLK, which has a rate at the nominal center frequency of the ultrasound signal prior to sampling.

Abstract: A rectangular antenna array includes a plurality of systolic vertical line arrays. Each vertical line array includes a plurality of signal processors. Within each line array, the signals received at any one moment are held or delayed as required, and the processors progressively form partial sums in an upward direction during first clock intervals and in a downward direction during alternate clock intervals. During each clock intervals, complete sums for one sample interval appear at an end of the vertical line array. The sums appear alternately at the top and the bottom of the line arrays. Beamforming in the horizontal direction is accomplished with systolic horizontal adders coupled to the tops and bottoms of the vertical line arrays. The horizontal adders transfer information and add in one direction during first clock intervals, and then in the other direction during third clock intervals of a four-interval cycle.

Abstract: A method and apparatus steers the returning beams of a receiver in a swath bathymetric system to an actual target based on prior steering angle information for the target and using an algorithm which demonstrates a linear relationship between the phase of the return beam and the steering angle therefor. The receiver comprises a plurality of transducing elements which each emit a signal. The array is divided into two groups of elements which are processed and combined to form beams for each group which are steered to the known steering angle for the target. Beams are then steered to a slightly offset angle to produce an offset beam. Using an equation to define each return beam according to phase and error between prior known and actual steering angles for the target, the error value can be reduced to zero to provide an accurate measurement of the actual steering angle for the target.

Abstract: The intensity profile of an ultrasound beam in an ultrasound imaging system is adjusted by driving the individual piezoelectric crystals with drive signals having adjustable pulse durations. The duration of the drive pulse determines the frequency spectrum of the pulse and therefore determines the amplitude of the emitted ultrasound wave. The pulse durations may be selected such as to compose a desired profile of the ultrasound beam.

Abstract: Delay time data for using the transducers arranged within a probe, for transmitting and receiving an ultrasonic beam, is stored in a memory. The amount of this delay time data is less than that required for using all transducers. The delay time data stored in the memory is interpolation-processed, thereby providing additional delay time data. The sum of the delay time data stored in the memory and the additional delay time data obtained by the interpolation-processing suffices to use all the transducers incorporated in the probe.

Abstract: An object detecting system including an ultrasonic transducer element array including first to N-th ultrasonic transducer elements, a first means for intermittently supplying burst driving pulses to the ultrasonic transducer elements at different times in each of successive intermittent periods. Also, the object detecting system includes a second means coupled between each of the first to N-th ultrasonic transducer elements and the first means for applying the burst driving pulses to the first to N-th ultrasonic transducer elements, successively.

Abstract: An ultrasonic imaging system for transmitting ultrasonic pulses into an object and detecting reflected ultrasonic waves therefrom. The system is provided with delay lines for real time imaging. The system comprises a probe means having a transmitting bundle of acoustic waveguides for transmitting ultrasonic pulses into an object. The transmitting bundle includes the delay lines which consists of having cladded acoustic waveguides of different lengths for introducing different delays in the ultrasonic pulses carried by each waveguide.

Abstract: A switch matrix for a transceiver of ultrasonic waves containing a configuration of electroacoustic transducer elements in which in succession proceeding over the arrangement a group of transducer elements can be activated, contains a number of inputs (K1, K2, K3, K4), the number corresponding to the number of transducer elements of a group which are each connected to one of the activated transducer elements, an equal number of outputs (R1, R2, R3, R4) connected to delay elements and a large number of switches T11, T12, . . . , T44) to establish each of the connections required for electronic focusing between the inputs and the outputs. Each input line (K1) is connected to a number of switches (T11, T12, T13, T14), this number corresponding to the number of transducer elements of a group. The switches of the switch matrix are activated through a control circuit (50) over a number of control lines (L1, L2, L3, L4), this number corresponding to the number of transducer elements of a group.

Abstract: A two-dimensional ultrasonic phase array is a rectilinear approximation to a circular aperture and is formed by a plurality of transducers, arranged substantially symmetrical about both a first (X) axis and a second (Y) axis and in a plurality of subarrays, each extended in a first direction (i.e. parallel to the scan axis X) for the length of a plurality of transducers determined for that subarray, but having a width of a single transducer extending in a second, orthogonal (the out-of-scan-plane, or Y) direction to facilitate dynamic focussing and/or dynamic apodization. Each subarray transducer is formed of a plurality of sheets (part of a 2-2 ceramic composite) all electrically connected in parallel by a transducer electrode applied to juxtaposed first ends of all the sheets in each transducer, while a common electrode connects the remaining ends of all sheets in each single X-coordinate line of the array.

Abstract: A method for receiving a return signal from each of plurality M of different beam directions in media excited by a single excitation event, is to: assign each of the M directions to be substantially equally separated, by a small angular displacement from a central beam; excite the media with a single energy beam transmitted to be focused at the central beam; receive a return signal from the central beam; and for each of the M different beam directions, independently rotating the phase of the received return signal by an amount predetermined to displace the apparent focus of the response beam to the associated direction.

Abstract: An ultrasonic wave sensor wherein the transmitter and receiver include a linear array of transducers. Each of the transducers of the transmitter are driven by plural pulsed signals in each of a plurality of intermittent time periods. The timing of the pulsed signals to each of the transducers is controlled to produce wave fronts that interfere to produce combined wave fronts at angles to the array of transducers. Three-phase charge coupled devices in conjunction with three-phase clocking pulses are used to produce pulsed signals of predetermined delays to each of the transducers. The receiver uses three-phase charge coupled devices and three-phase clocking pulses to process returned signals.

Abstract: An oceanographic mapping system comprises a narrow beam acoustic transmitting transducer, a beam scanning system and controls for controlling the timing of the transmitted pulses and the movement of the bearing scanner. A receiver is also provided to receive the echoes generated by the acoustic pulses and a range calculated as provided for determining the delay between the transmitted pulses and their corresponding echoes. A mapping system is also provided which communicates with the range calculator and the beam scanner and is operable to process the range and bearing signals that generate the profile of the target area. The method of mapping includes the step of transmitting a series of acoustic signals before the first echo generated by a signal of the transmitted series is received by the receiver, thereby to increase the speed at which mapping can be accomplished.

Abstract: An acoustic sensing system to measure a geometry parameter such as, for example, position, orientation and/or shape of an object. The system includes a transmitter for transmitting acoustic wave energy at a single frequency, which acoustic wave energy, in an operating system, interacts with the object in a sensing region to provide reflected or scattered wave energy. A sensor mechanism consisting of many acoustic transducers is positioned to receive the reflected or scattered wave energy, each transducer being operable to convert the received acoustic wave energy to an electrical signal. A processor is connected to receive the electrical signals from the plurality of acoustic transducers; the processor is operable to obtain amplitude and phase information with respect to the electrical signal from each of the transducers, the amplitude and phase information from each of the plurality of transducers being combined and analyzed to derive a geometric parameter of the object.

Abstract: A transmitting/receiving circuit for an acoustic transducer (W1, W2) wherein the transmitting transducer (W1) is sequentially controlled by different modulated carrier frequencies (f1, f2), where the control is first matched to the inherent frequency (f1) of the transducer (W1) and afterwards the control of the transducer (W1) is by a frequency (f2) outside of the inherent frequency. During a signal reception by the receiving transducer (W2), a lock-out of a phase-locking circuit (PLL) is detected, where with an object to be measured is in a near range an active lock-out due to the frequency shift of the reception signal outside a frequency bandwidth of the phase-locking circuit is detected, and where with an object to be measured is in a far range, a passive lock-out is detected due to the fact that the reception signal amplitude falls below a noise level.

Abstract: Disclosed herein is an omnidirectional distance measurement system which transmits and receives ultrasound waves using as many as four transmitting-receiving transducers having specially shaped beamwidths. Through the use of four such ultrasonic transducers, the system may be set up to obtain any beamwidth from 5.degree. up to 360.degree. in both the horizontal and vertical planes. In the preferred embodiment, the present invention is able to detect the distance and direction to up to four objects in a prescribed work area at any one time and may also detect the speed of any one of the objects if desired.

Abstract: Imaging apparatus including an array of transmitters for simultaneously transmitting more than two coded signal beams in different directions to cover different regions of a field of view, said beams being modified by objects within said field of view, signal means for providing individual coded signals to respective transmitters, at least one receiver for simultaneously receiving plural coded modified signals derived from the coded signal beams, and a processor for separating the plural coded modified signals of different codes and processing them into an image signal.

Abstract: A method of imaging an object by the ultrasonic or electromagnetic wave by mechanically or electronically scanning the ultrasonic or electromagnetic wave transmitting/receiving system to transmit the ultrasonic or electromagnetic wave beam spreading in space of the object and using the trace (TOF locus) from the transmission to the reception while receiving the reflected wave from the object, and sequentially reproducing the line image at the central line of the synthetic aperture range using the received signal group from the scanning points in the synthetic aperture range to sequentially image the area to be imaged while scanning the ultrasonic or electromagnetic wave transmitting/receiving system. An imaging apparatus applied with the method has a relatively simple hardware structure for reproducing the image and is also able to perform the operation in real time.

Abstract: In an ultrasonic beam former for phasing and adding received signals supplied from respective elements of an ultrasonic transducer array and for producing the received output in conformity to a desired wave front, a plurality of sampling delay means for sampling and delaying the received signal supplied from each element are disposed for each channel. The plurality of delay means effect the sampling operation successively and alternately. Outputs of delay means are selected by switches activated in response to the alternate sampling operation. As a result, the sampling rate per signal channel is increased.

Abstract: In the ultrasonic wave phase matching diagnostic apparatus described in the specification, an array of ultrasonic transducers is arranged to transmit ultrasonic waves to an object to be investigated and to receive ultrasonic waves returned from the object. Focusing of the waves to a point in the object is accomplished by selective delaying of the transmitted signals from each of the ultrasonic transducers, and similar delays are imposed on received signals to define a focal point for signals received from the object. Scanning of the object is provided by stepwise changes in the ultrasonic transducers used for transmitting and receiving ultrasonic signals, and half-pitch scanning may be effected by using different numbers of ultrasonic transducers for transmission and reception of the ultrasonic waves.

Abstract: Phased-array apparatus has a number of ultrasonic transducer elements (E1 to E64) to which are associated delay line elements (M1, T1 to M64, T64, W1-1, W1-2, N1 to W16-1, W16-2, N16; W1 to W16; VL1 to VL64, VR1 to VR16) to provide reception. In order that the control angle may be adjusted with high accuracy, according to the inventive principles delay line elements are provided for the received signals with a short and with a long delay, and several adjacent channels are combined for signal processing. Due to this arrangement, economical constructions of embodiments of the invention are realized.

Abstract: An ultrasonic imaging apparatus comprises an ultrasonic transducer comprised of a plurality of ultrasonic transducer elements arranged in one direction, a transmission section for driving the ultrasonic transducer to radiate first and second ultrasonic beams from the ultrasonic transducer at a time in their different directions, and a receiver section for processing echo signals which are obtained from the ultrasonic transducer means and for outputting first and second television signals. Television signals are displayed as two lines of raster on a monitor.

Abstract: An ultrasonic sensor system particularly for automatic door openers of a swinging door type, in addition to sensors (14) for people approaching a door for controlling opening and closing purposes, has at least one microprocessor controlled ultrasonic beam transducer (40, 41) for projecting an expanded unidirectional ultrasonic beam in a selected detection zone in the path of the swinging door and an ultrasonic detector for converting reflected ultrasonic beam energy into an analog electrical signal which constitute an acoustical image of objects in and bounding the selected detection zone. This acoustical image is stored or, a number characterized thereof is stored and this acoustic image is then compared with a later acoustical image of an object in the selected detection zone and then the comparison is used to signal a lack of correlation between the first and second acoustical images to produce a signal preventing operation of the door opening.

Abstract: Ultrasound imaging apparatus having an array of electro-acoustic transducer rings, means for exciting said transducer rings in sequence so as to cause them to transmit successive pulses of pressure waves along a path at intervals at least equal to the time of transit of the pressure waves to a maximum range and back to the array, dynamically controlled delays respectively coupled to each transducer ring that bring the electrical signals the transducers supply in response to pressure of waves of each pulse that are reflected along a given range into reasonable phase coherence, processing means coupled to the delays so as to provide a composite signal, and a summing memory coupled to receive the composite signal.

Abstract: An ultrasonic imaging processing system includes transducers and means to generate in an analog fashion, in-phase and quadrature phase signals. These signals are converted to digital form and a butterfly phase rotator circuit is employed to correct for phase differences in beam steering and focusing. In particular, speed and simplicity is achieved through the utilization of read only memory means providing appropriate function values for phase correction in conjunction with digital multiplication and summing circuitry.

Abstract: An ultrasonic antenna is mounted with an ultrasonic transducer on an agricultural implement and directs an ultrasonic burst directly towards the ground in front of the agricultural implement for the purpose of range finding. The transducer receives the reflected signal and, following signal processing, a computation is made of the height of the reference point on the implement above the ground. Ground tillage, seeding, and similar equipment including above ground harvesting implements can be controlled with the equipment. The antenna is characterized by a moulded body having a sensor mounting at one end and an opening at the other end with co-operating first and second concave surfaces for reflecting the ultrasonic beam between the sensor and the opening and vice versa.

Abstract: A method and apparatus for digitally delaying ultrasound signals, which are reflected from a boundary surface inside of an examination subject, upon reception of the signals at an ultrasound receiver employ, in each channel, a shift register, a first multiplexer, another register, and interpolator and a further multiplexer to effect a selected delay. A number of interpolated ultrasound signals is formed from two successively received ultrasound signals. If the successive ultrasound signals are shifted by .DELTA..tau., the interpolated ultrasound signals will be shifted by a smaller time difference relative to each other, dependent on the fineness of the interpolation. That interpolated ultrasound signal or that received ultrasound signal having a delay value which is closest to a selected desired delay value is employed for further signal processing. A high precision in the chronological resolution can thus be achieved with a relatively low sampling rate in comparison to the chronological resolution.