Abstract: A wedge for on-line inspection of a weld includes a wedge body defining a coolant channel and at least one couplant channel, and a coolant input port in fluid connection with a first end of the coolant channel. The wedge body has a surface for disposing a phased array ultrasonic transducer comprising an array of ultrasonic elements. The coolant channel is formed in proximity to the surface for disposing the phased array ultrasonic transducer such that coolant flowing through the coolant channel maintains the phased array ultrasonic transducer below a predetermined temperature without obstructing the array of ultrasonic elements.

Abstract: An ECU of an object detection device stops transmission of search waves from a plurality of ultrasonic sensors when a vehicle travels at a predetermined speed or more, and counts the frequency of receiving waves with an intensity of not less than a threshold intensity for each of the plurality of ultrasonic sensors. The ECU acquires a first count that is a count of the frequency in a first sensor that is one of the plurality of ultrasonic sensors, and a second count that is a count of the frequency in a second sensor different from the first sensor. The ECU determines that snow accretion has occurred on the first sensor if the first count is smaller than the second count, and a difference between the first count and a representative value that is set based on the second count is not less than a predetermined value.

Abstract: An ultrasonic testing device that can make a robotic testing system reach the surface of a complex curved composite workpiece that is not easy to reach and perform a quality testing. By pumping a coupling liquid into the device so that the coupling liquid enters a waveguide and jets onto the surface of the workpiece, an ultrasonic wave can be transmitted in the waveguide and reach the surface of the workpiece and penetrate the workpiece, thereby achieving the purpose of quality testing of the workpiece. By providing two ultrasonic testing devices without a waveguide on both sides of a tested workpiece, respectively, and by mounting the waveguide on one side or both sides of the ultrasonic testing devices, it is possible to transmit the ultrasonic waves to the surface of the workpiece or to receive the ultrasonic waves from the surface of the workpiece.

Abstract: An end effector includes a first portion having a first specific acoustic impedance value, and a second portion having a second specific acoustic impedance value less than the first specific acoustic impedance value. The first portion may include a proximal end segment and a distal end segment. The proximal end segment and the distal end segment are composed of a first material. The second portion may include an insert segment composed of a second material. The insert segment is located between the proximal end segment and the distal end segment along the longitudinal axis of the end effector. The insert segment functions to bridge or fill a nodal energy gap defined by the end effector.

Abstract: An apparatus and method for ultrasonic non-destructive testing provides an elongate strip of ultrasound transmissive material coupled at a proximal end to an object under test. The elongate strip has a transverse cross-section with a width and thickness giving an aspect ratio greater than unity and matched to the ultrasonic transducer such that excitation induces an ultrasonic signal to propagate along the elongate strip to the proximal end and to enter the object under test. These pulses are particularly suited for time-of-flight measurements, thickness measurements, crack measurements and the like. The elongate strip helps to separate the transducer from a potentially hostile environment associated with the object under test. The elongate strip also has a large area of contact with the object under test allowing efficient transmission of energy into the object under test.

Abstract: An apparatus and method for ultrasonic non-destructive testing provides an elongate strip of ultrasound transmissive material coupled at a proximal end to an object under test. The elongate strip has a transverse cross-section with a width and thickness giving an aspect ratio greater than unity and matched to the ultrasonic transducer such that excitation induces a substantially non-dispersive ultrasonic signal to propagate along the elongate strip to the proximal end and to enter the object under test. These non-dispersive pulses are particularly suited for time-of-flight measurements, thickness measurements, crack measurements and the like. The elongate strip helps to separate the transducer from a potentially hostile environment associated with the object under test. The elongate strip also has a large area of contact with the object under test allowing efficient transmission of energy into the object under test.

Abstract: An ultrasonic signal coupling assembly including ultrasonic transducers attached to one or more ultrasonic couplers configured to be coupled to an exterior surface of a pipe. A height of the ultrasonic coupler or couplers is greater than a thickness of the pipe by a factor of about five or more, and a length of the ultrasonic coupler or couplers is greater than the height of the ultrasonic coupler or couplers.

Abstract: An inspection device (300) has an ultrasonic transducer (304) encased in a couplant block (302) mounted in a housing (328). The housing (328) has a pair of encoders (340, 342) mounted thereto. The transducer (304) is mounted to scan perpendicular to the contact surface (306) of the block (302). A coupling block with a PTFE layer on the contact surface is also provided.

Abstract: Apparatus for non-invasive measuring of the sound velocity of a fluid flowing in a tubing having a small internal diameter for the fluid passage as compared to the tubing wall thickness and having points of two different and known transverse length with a sensor mounted at each point and a delay line adjacent to the tubing at each point. Each sensor is connected to a circuit that provides ultrasonic energy signals that are transmitted through the tubing walls, the flowing fluid and the delay line to be reflected back to the sensor from which the round trip transit time of the signals is measured and the sound velocity calculated from the two measured round trip transit times and the differential between the known transverse lengths.

Abstract: An apparatus and method for ultrasonic non-destructive testing provides an elongate strip of ultrasound transmissive material coupled at a proximal end to an object under test. The elongate strip has a transverse cross-section with a width and thickness giving an aspect ratio greater than unity and matched to the ultrasonic transducer such that excitation induces a substantially non-dispersive ultrasonic signal to propagate along the elongate strip to the proximal end and to enter the object under test. These non-dispersive pulses are particularly suited for time-of-flight measurements, thickness measurements, crack measurements and the like. The elongate strip helps to separate the transducer from a potentially hostile environment associated with the object under test. The elongate strip also has a large area of contact with the object under test allowing efficient transmission of energy into the object under test.

Abstract: An apparatus and method for ultrasonic non-destructive testing provides an elongate strip of ultrasound transmissive material coupled at a proximal end to an object under test. The elongate strip has a transverse cross-section with a width and thickness giving an aspect ratio greater than unity and matched to the ultrasonic transducer such that excitation induces a substantially non-dispersive ultrasonic signal to propagate along the elongate strip to the proximal end and to enter the object under test. These non-dispersive pulses are particularly suited for time-of-flight measurements, thickness measurements, crack measurements and the like. The elongate strip helps to separate the transducer from a potentially hostile environment associated with the object under test. The elongate strip also has a large area of contact with the object under test allowing efficient transmission of energy into the object under test.

Abstract: An apparatus and method for ultrasonic non-destructive testing provides an elongate strip of ultrasound transmissive material coupled at a proximal end to an object under test. The elongate strip has a transverse cross-section with a width and thickness giving an aspect ratio greater than unity and matched to the ultrasonic transducer such that excitation induces a substantially non-dispersive ultrasonic signal to propagate along the elongate strip to the proximal end and to enter the object under test. These non-dispersive pulses are particularly suited for time-of-flight measurements, thickness measurements, crack measurements and the like. The elongate strip helps to separate the transducer from a potentially hostile environment associated with the object under test. The elongate strip also has a large area of contact with the object under test allowing efficient transmission of energy into the object under test.

Abstract: Apparatus and method for non-invasive measuring of the sound velocity of a fluid, such as a liquid, flowing in a tubing having points of two different and known transverse length has one sensor mounted at each point connected to a circuit that provides signals to each sensor that are returned to it after passing through the tubing wall and flowing fluid and reflection from the tubing internal wall opposing each sensor and from which the round trip transit time of the signals is measured and the sound velocity calculated from the two measured round trip transit times and the differential between the known transverse lengths. Flexible tubing is placed in the slot of a measuring head which deforms it to provide the two points at one location or the slot has two sections of different transverse length along its length with a point at each section.

Abstract: An ultrasonic sensor includes a transmitting device, a receiving device, and a circuit device. The circuit device determines that the receiving device receives an ultrasonic wave reflected from an object, when an output voltage of the receiving device is equal to or greater than a first threshold. The circuit device includes a humidity detection section configured to detect an ambient humidity of the transmitting and receiving devices and a threshold adjustment section configured to calculate, based on the detected ambient humidity, a sound pressure of the ultrasonic wave that is received by the receiving device after propagating over a round-trip distance between the ultrasonic sensor and the object. The threshold adjustment section reduces the first threshold, when the output voltage corresponding to the calculated sound pressure is less than a second threshold that is greater the first threshold.

Abstract: An apparatus and method for ultrasonic non-destructive testing provides an elongate strip of ultrasound transmissive material coupled at a proximal end to an object under test. The elongate strip has a transverse cross-section with a width and thickness giving an aspect ratio greater than unity and matched to the ultrasonic transducer such that excitation induces a substantially non-dispersive ultrasonic signal to propagate along the elongate strip to the proximal end and to enter the object under test. These non-dispersive pulses are particularly suited for time-of-flight measurements, thickness measurements, crack measurements and the like. The elongate strip helps to separate the transducer from a potentially hostile environment associated with the object under test. The elongate strip also has a large area of contact with the object under test allowing efficient transmission of energy into the object under test.

Abstract: The present invention is seen to provide a new methodology, testing system designs and concept to enable in situ real time monitoring of the cure process. Apparatus, system, and method for the non-destructive, in situ monitoring of the time dependent curing of advanced materials using one or more differential ultrasonic waveguide cure monitoring probes. A differential ultrasonic waveguide cure monitoring probe in direct contact with the material to be cured and providing in situ monitoring of the cure process to enable assessment of the degree of cure or cure level in a non-cure related signal variances (e.g., temperature) independent calibrated response manner. A differential ultrasonic waveguide cure monitoring probe including a transducer coupled to a waveguide and incorporating correction and calibration methodology to accurately and reproducibly monitor the cure process and enable assessment of cure level via ultrasonic reflection measurements.

Abstract: Disclosed is an input apparatus including a coplanar line formed on the surface of a substrate so as to pass through the vicinity of a position at which a user performs an operation, terminating resistor placed at one end of the coplanar line and a microcomputer module at the other end. The microcomputer module has a signal transmitter for outputting a signal to the coplanar line. When the user operates a key, the impedance of the coplanar line changes and a reflected wave is produced. A signal detector in the microcomputer module detects the reflected wave and outputs received-signal strength information, which indicates the strength of the signal included in the reflected wave, to a computing unit. Based upon the received-signal strength information and strength of the signal that has been output by the signal transmitter, the computing unit in the microcomputer module discriminates the key that has been operated and specifies the entered instruction.

Abstract: The invention relates to a system for damping the reflection wave at the open end (6) of a magnetostrictive sensor system, which has at least one magnet device (2), which can be moved relative to a measuring wire (1) that can be deflected mechanically and that experiences a deflection under the influence of a current pulse (3), which deflection can be processed by a signal device (5), wherein the system has at least one damping part (8) lying against the measuring wire (1) at the open end (6), said damping part having a tubular damping element (9), which can be clamped to the measuring wire (1) by means of a sleeve-like enclosure (11).

Abstract: A spiral wound module assembly comprising: a permeate collection tube, at least one membrane envelope wound about the permeate collection tube, an outer module housing, and at least one acoustic transducer located adjacent to the permeate collection tube. Several embodiments are disclosed including a stand-alone probe adapted for insertion into the permeate collection tube. In several other embodiments, one or more transducers are secured to the inner surface of the permeate collection tube.

Abstract: An ultrasonic receiver according to the present invention includes: a wave propagating portion 6, which defines a first opening 63 and a waveguide 60 that makes an ultrasonic wave, coming through the first opening 63, propagate in a predetermined direction; and a propagation medium portion 3, which has a transmissive interface 61 and which is arranged with respect to the waveguide 60 such that the transmissive interface 61 defines one surface of the waveguide 60 in the direction in which the ultrasonic wave propagates. The interface 61 is designed and arranged with respect to the waveguide 60 such that as the ultrasonic wave propagates along the waveguide 60, each portion of the ultrasonic wave is transmitted into the propagation medium portion 3 through the interface 61 and then converged toward a predetermined convergence point. The receiver further includes a sensor portion 2, which is arranged at the convergence point 33 to detect the ultrasonic wave converged.

Abstract: Disclosed herein is a passage detection apparatus capable of detecting a passage of an object in a specific space. The passage detection apparatus includes a transmitting device, a receiving device, and a shielding member. The transmitting device is provided with a vibration generating source. The receiving device is arranged at the position corresponding to the transmitting device across the specific space. The shielding member has a through-hole, and is arranged so as to be interposed between the transmitting device and the receiving device. The vibration transmitted from the transmitting device reaches the receiving device via the through-hole and a passage route of the object. On the other hand, the reception of the vibration, reflected in the specific space, by the receiving device is suppressed by the shielding member.

Abstract: An ultrasonic receiver according to the present invention includes a first horn having a first large opening and a first small opening which are an incidence end and an outgoing end of an ultrasonic wave; a second horn having a second small opening and a second large opening which are an incidence end and an outgoing end of the ultrasonic wave, the first and second horns being located such that the first and second small openings face each other, and such that propagation directions of the ultrasonic wave in the first and second horns match each other; and at least one ultrasonic receiver main body provided between the first and second small openings, the ultrasonic receiver including a surface parallel to the propagation direction and detecting the ultrasonic wave which has propagated in the first horn and then is incident on the parallel surface.

Abstract: Disclosed herein is a passage detection apparatus capable of detecting a passage of an object in a specific space. The passage detection apparatus includes a transmitting device, a receiving device, and a shielding member. The transmitting device is provided with a vibration generating source. The receiving device is arranged at the position corresponding to the transmitting device across the specific space. The shielding member has a through-hole, and is arranged so as to be interposed between the transmitting device and the receiving device. The vibration transmitted from the transmitting device reaches the receiving device via the through-hole and a passage route of the object. On the other hand, the reception of the vibration, reflected in the specific space, by the receiving device is suppressed by the shielding member.

Abstract: An ultrasonic probe has a probe proper, a connector and a cable for electrically connecting between the probe proper and the connector. The probe proper includes a transducer that converts between ultrasonic wave and electricity, and a phase change member having a property to cause a phase change of from solid to liquid at a particular temperature reached in an operation time period of the transducer and a phase change of from liquid to solid at lower than the particular temperature.

Abstract: In order to check a material web (12), in particular a film web, with regard to the correct arrangement of a tear-off strip (11) extending in the longitudinal direction of the material web (12), ultrasonic transmitters are used, specifically an ultrasonic transmitter (11) on the one hand and an ultrasonic receiver (19) on the other hand. The sensors are arranged on opposite sides of the material web (12) in such a way that, if appropriate, focused ultrasonic waves are aimed specifically at the region of the tear-off strip (11). If a tear-off strip (11) is missing, an appropriate signal is generated by the ultrasonic receiver (19).

Abstract: An apparatus for making pulsed acoustic measurements to determine particle size in a sample (1) such as a colloid. The apparatus includes two elctrodes (2) between which an electric voltage is applied to the sample. The voltage is applied in short pulses. The applied voltage generates an acoustic signal, such as a sound wave (5), in the sample which is detected with a transducer (3) after the wave (5) has passed through a delay element (4). The delay element (4) is used to introduce enough of a time delay between the application of the voltage pulse and sound wave (5) reaching the transducer so that the received wave's signal can be isolated from any signal generated in the transducer (3) by the applied voltage. The delay element (4) and the transducer (3) are arranged into a geometry, or, alternatively, the delay element (4) is shaped, so that any reflections of the sound wave (5) from the sidewalls of the delay element (4) are deflected away from the transducer (3).

Abstract: A foreign object impact sensor for use with combustion turbines utilizes a passive acoustic waveguide within the turbine to receive acoustic signals from foreign object impact. The magnitude of these signals is displayed and or stored using a lighted display or other suitable indicating device. The information is also recorded and stored, so that a spectrum signature can be obtained from Fourier analysis.

Abstract: An obstacle detecting system for vehicles has an ultrasonic vibrator having a vibration plate and mounted on a vehicle to transmit and receive an ultrasonic wave. An obstacle is detected in response to an output signal of the ultrasonic vibrator. When the temperature around the ultrasonic vibrator is below a predetermined temperature corresponding to snowfall, the system calculates a ratio of a period of reverberating vibration of the ultrasonic vibrator relative to a predetermined time period following an ultrasonic wave transmission, and determines accumulation of snow when the calculated ratio exceeds a predetermined time ratio. The system notifies an abnormality of the ultrasonic vibrator arising from the accumulation of snow.

Abstract: An obstacle detecting system for vehicles has an ultrasonic vibrator having a vibration plate and mounted on a vehicle to transmit and receive an ultrasonic wave. An obstacle is detected in response to an output signal of the ultrasonic vibrator. When the temperature around the ultrasonic vibrator is below a predetermined temperature corresponding to snowfall, the system calculates a ratio of a period of reverberating vibration of the ultrasonic vibrator relative to a predetermined time period following an ultrasonic wave transmission, and determines accumulation of snow when the calculated ratio exceeds a predetermined time ratio. The system notifies an abnormality of the ultrasonic vibrator arising from the accumulation of snow.

Abstract: An ultrasonic test head for ultrasonically testing flaws in a workpiece includes a common housing. An ultrasonic transducer configuration is disposed in the common housing. At least one ultrasonic transducer array is disposed in the common housing for operation in a pulse echo mode for transverse waves propagating in a workpiece. The ultrasonic transducer configuration includes at least two acoustically separate ultrasonic transducers to be operated in a transmit/receive mode for longitudinal waves propagating near a surface in the workpiece. In a method for operating the ultrasonic test head, each ultrasonic transducer array or arrays is operated in a transmit/receive mode.

Abstract: A sensing apparatus includes a pulse recirculating circuit operatively connected to at least one ultrasonic delay sensor or other device for recirculating pulses therethrough, and a measurement difference output circuit for generating an output signal based upon a difference between first and second measurements of the at least one ultrasonic delay sensor. The pulse recirculating circuit preferably comprises a pulse generator for generating a series of input pulses to the ultrasonic delay sensor, and a pulse detector for detecting a series of output pulses after propagation through the ultrasonic delay sensor. Moreover, the measurement difference output circuit preferably includes an up-down counter for counting pulses during the first measurement in one direction and for counting pulses during the second measurement in an opposite direction. Accordingly, the remaining counter contents represent a difference in delay between the first and second measurements.

Abstract: A beam forming and focusing processing circuit for use in an ultrasound imaging system. The system incorporates a plurality of the processing circuits which differentially delay imaging signals in order to generate an output in which the imaging signals from each circuit implement the desired differential delay. Each of the processing circuits include a first delay line having a plurality of delay units operable for receiving the imaging signals and converting same into sampled data. A selection control circuit is operable for reading the sampled data from a selected first delay unit of the first delay line so as to correspond to a selected first time delay to accommodate fine delay resolution of the imaging signals. A second delay line having a plurality of delay units is operable for sensing the sampled data from the selected first delay unit.

Abstract: An apparatus includes an ultrasonic delay sensor or device having a delay related to the sensed quantity; a pulse recirculating circuit for recirculating pulses through the ultrasonic delay sensor for generating a pulse repetition signal having a frequency related to delay of the ultrasonic delay sensor; and an output circuit for generating an output signal related to delay in the ultrasonic delay sensor based upon a difference in phase velocity between the pulse repetition signal and a time base signal. The output circuit preferably includes a first multiplier for multiplying the pulse repetition signal by a first number, and a second multiplier for multiplying the time base signal by a second number to have a frequency substantially the same as the multiplied pulse repetition signal. The effects of undesired reflections in the ultrasonic delay device may also be reduced or suppressed. Method aspects of the invention are also disclosed.

Abstract: The number of transducers in the scanning of an ultrasonic field from an object is reduced by providing ultrasonic collectors at spaced apart locations in the medium and transmitting the ultrasonic waves which are collected to a transducer through waveguides or paths having different transit times. The waveguides can be individually of different lengths or can be of equal length and terminate at different distances along a common collecting waveguide.

Abstract: A measurement structure for determining the thickness of a specimen without mechanical contact but instead employing ultrasonic waves including an ultrasonic transducer and an ultrasonic delay line connected to the transducer by a retainer or collar. The specimen, whose thickness is to be measured, is positioned below the delay line. On the upper surface of the specimen a medium such as a drop of water is disposed which functions to couple the ultrasonic waves from the delay line to the specimen. A receiver device, which may be an ultrasonic thickness gauge, receives reflected ultrasonic waves reflected from the upper and lower surface of the specimen and determines the thickness of the specimen based on the time spacing of the reflected waves.

Abstract: A method and an apparatus for detecting and identifying a contaminant, such as ice, on the surface of a structure, such as a wing, are disclosed. The apparatus has a probe having a delay block with an interface apt to be placed flush with the surface of the structure and two faces at the same angle of inclination relative to the interface and having transmission and reception transducers each oriented perpendicularly to one of the faces. The block has an acoustic impedance lying in the range of 0.7 to 3.times.10.sup.6 kg/m.sup.2.s. It further has an energization and analysis unit for applying an electrical energization pulse to the transmission transducer and comparing the amplitude and the phase of the echo from the interface with a reference echo corresponding to no contamination.

Abstract: Improved ultrasonic energy transducers each include a material contacting member secured to a piezoelectric element at an interface region between oppositely operated first and second regions of the piezoelectric element. The material contacting member intensifies and amplifies movement of the interface region as the first and second regions of the piezoelectric element operate in a push-pull mode relative to the interface region. The first and second regions of the piezoelectric element can be electrically driven to move the material contacting member for transmission of ultrasonic energy or mechanically driven by the material contacting member for receipt of ultrasonic energy. A variety of piezoelectric elements can be used in the improved transducers including, for example, generally rectangular bars and discs segmented into two or more portions. A variety of material contacting members can also be used including, for example, a cylindrical stud and a more narrow dowel.

Abstract: In a detection device of the presence of frost and/or measuring the thickness of the frost by ultrasound, a probe with a piezoelectric ultrasonic transducer generates an ultra-sonic acoustic emission wave and detects ultrasonic acoustic echo waves reflected by the frost. An actuating device for the probe is arranged to provide to the transducer electrical energizing signals. The probe comprises: a frost detector placed in front of the transducer and constituted of a material having an acoustic impedance between 30.times.10.sup.5 and 44.times.10.sup.5 kg m.sup.-2 s.sup.-1. This detector has a surface designed to be exposed to the surrounding atmosphere to be covered with frost. An acoustic delay device is adapted to ensure acoustic coupling and adaptation between the transducer and the detector and to separate in time the ultrasonic emission add reflected waves. A body of heat insulating material covers the assembly of the detector, the transducer and the acoustic delay device.

Abstract: A non-destructive method and apparatus for inspecting materials in excess of 500.degree. C. includes a dual transducer disposed upon a delay line suitable for operation at the elevated temperatures. The delay line is divided into two parts acoustically isolated and is cooled by a fluid to maintain the surface upon which the transducers are mounted at a safe operating temperature.

Abstract: An ultrasonic diagnostic apparatus protected from multi-reflection of sound echoes. Multi-reflection is avoided by eliminating the reflection from the surface of an electro-sound transducer. This invention eliminates the surface reflection of the transducer by following three methods:(a) changing a direction of each surface of an array of transducer elements to direct the reflected sound wave away from the main direction of the sound beam;(b) applying an acoustic matching layer to a surface of a piezo-electric device of the transducer to cancel out phases of sound waves reflected by the surfaces of the layer and the device; and(c) providing an acoustic matching surface on a front or back face of the piezo-electric device to cancel out phases of sound waves reflected by the surface of the device.

Abstract: A contactless self-scanning electro-elastic nondestructive testing technique is described for determining in real time the presence, location, number and size of defects present on the surface of a material under test. In one embodiment the apparatus includes means for inducing eddy currents or current flow in the surface of the conductive material. A magnetostrictive delay line is disposed parallel to the direction of current flow and equidistant and in fixed spatial relation with the surface. The presence of a crack or defect in the surface proximate to the delay line creates transverse eddy currents or transverse currents in the material which interact locally with the magnetostrictive delay line to induce elastic waves in the delay line. The elastic waves are generated in the delay line only at locations corresponding to the edges of the defects. An ultrasonic sensor coupled to the delay line is used to detect the elastic waves travelling in the delay line.

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.

Abstract: A convergent ultrasonic beam is formed by an emitter made as a sphere and directed to a piece under test. Having been reflected from the surface of the piece and from the defect, the ultrasonic beams are separated in space. The ultrasonic beam carrying information on the defect is displayed.

Abstract: Ultrasonic reflections are received by a transducer array whose resultant signals are passed through an array of time-varying delay lines to provide focusing at all depths. The delay lines are made up of a combination of two components, one increasing and one decreasing with the distance to the axis of the array. This combination minimizes the range of delay variations required over the depth range. When using charge coupled devices as delay elements, this combination minimizes the required range of clock frequencies.