EP0000068A1 - Apparatus for ultrasonic imaging using dynamic focussing - Google Patents

Abstract

The receiver (80) of an ultrasound system is divided into concentric parts (81, 82, 83), each of which is assigned to a memory (130, 131, 132, 133). The sound waves arriving between the center (81) and the outer rinsing (82, 83) are delayed by dividing the outer receivers and memories (132, 133) with a higher clock frequency (141, 142, 143) or by providing delay lines (201, 202) are. The distribution of the signals is sorted with a suitable logic circuit (135, 137, 139, 148, 170) so that signals suitable for the screen can be taken from the memories (130, 131, 132, 133).

Description

The invention relates to a device for displaying a body on a television picture and in particular to the use of dynamic focusing that can be applied to ultrasound imaging systems.

Over the past two decades, ultrasound technology has become increasingly important in clinical diagnostics. Ultrasound technology has already been used in the fields of gynecology, neurology and cardiology, among other things, e.g. was successfully used to visualize subcutaneous blood vessels (including smaller ones).

There are significant reasons for the use of ultrasound technology in medicine: Ultrasound differs from other types of radiation due to its harmless effect on living systems because it is purely mechanical wave nature. The ultrasound technology makes it possible to obtain information that cannot be obtained by other methods, for example by examining with γ and X-rays. Above all, the risk of injury when using ultrasound is much less than e.g. B. when using ionizing rays (y or x-rays). Ultrasound is mainly used as a pulse echo method in diagnostic technology, which involves pulses of ultrasound energy periodically from a piezoelectric transducer; e.g. B. lead-zirconate-titanate ceramic-based. Every small pulse of ultrasonic energy is directed as a sound wave at the patient's body, penetrating through various surface structures, if necessary. If an interface of the body has an irregularity at which the phase of the ultrasonic wave changes, part of the ultrasonic energy becomes thrown back again. After an ultrasound pulse is delivered, the ultrasound device is usually placed on reception in order to be able to convert reflected (or echo) signals from the body back into electrical signals. The time after which these echo signals return to the receiver is directly dependent on the distance of the reflection source and the speed of sound. The strength of the sound echo is also interesting because it provides information about the type of fault.

The echo of sound waves can be represented in different ways. On the one hand, there are devices with amplifiers with which the electrical signals corresponding to the received ultrasonic echo are increasingly applied to the vertically deflecting plates of a cathode ray tube. The exit of one _. The time generator is due to the horizontal deflection of the cathode ray tube. A constant repetition of the impulse / echo process, synchronized with the time generator, then leads to a still picture, so-called "A-scan", in which the time is proportional to the depth of penetration and vertical deflections signal existing disorder. The intensity of these vertical deflections is a measure of the intensity of the echo.

Another common type of pictorial representation of ultrasound waves is the so-called B-scan, in which the echo information corresponds to the usual television picture. ie the received echo signals are used to modulate the brightness of the screen per sampling point. This type of screen is specifically used for sound wave viewing through the body so that each intensity information occupies multiple scan lines of the screen and the successive positions are used to display successive lines on the screen. With this technique, a transmitted light image is scanned in one plane and the resulting image can be viewed directly or through a photograph or magnetic tape.

An object of the invention was to provide a device in which the ultrasound scanning through the body is carried out with a reflector which is mechanically guided over a certain angle with the same frequency as rotated for the deflection of the electron beam of a screen. The reflector would have to be turned sawtooth like the line drive of the screen to avoid losses. However, because of the inertia of the mirror mass relative to the inertia of an electron beam, this is practically impossible. Ultrasonic waves are therefore not easily suitable for display on an electrically controlled screen.

It is also known that ultrasound reflects at the boundary between a liquid and a gas phase. This has led to an ultrasound technique in which the ultrasound is passed through a closed liquid in which it has less losses as structure-borne noise. If, however, the reflecting scanning screen is in a liquid, such as water, the adjustment problem arises even more quickly (back) movement - because of the great internal resistance of the liquid after a slow movement - for display on the screen. This applies in particular to scanning devices with a large scanning range in which the internal resistance of the liquid prevents acceleration of the reflection screen.

The sound excitation or sensor plate of the devices described has limited dimensions, on which the limited penetration depth of the measurable ultrasonic waves depends. It is also known that ultrasonic waves can be directed with suitable lenses, as are described in US Pat. No. 3,598,559 and / or by dividing the ultrasound excitation and sensor system into different ones small parts connected by different delay lines. One type of focusing can be achieved, for example, by designing sound-absorbing components with a multiplicity of concentrically interposed disks of transmission elements which are connected via different delay lines. Because of the relatively low speed of sound, the path difference that the sound waves cross from the center of a transmitter to its edge zone on the way there and back via a theoretical focal point and back plays a major role if beam bundling is provided analogously to electromagnetic waves. The path difference between the short path from the focal point to the center of the transmitter to the path from the focal point to the edge of the transmitter must be compensated for with delay means in accordance with a double pass of the ultrasonic waves. Electrical delay lines on the way from the electrical exciter to the sound transducer have proven their worth.

It is also known to change the ultrasonic measuring depth by varying the delay lines. Non-changeable delay lines only allow an ultrasound measurement with a fixed predetermined focal point, which can be adapted to different problems for examination when the delay lines are varied. Finally, it must be noted that ultrasound waves stay longer in the body for deeper examination. An examination requires observation of the body at different depths. In the case of a more in-depth examination, the path or difference in path between the central receiving point and peripheral zones is somewhat equalized, which must be taken into account by setting the delay lines accordingly. Because of the large number of setting options for the delay lines, the technical scope and use of such devices is very complicated.

The object of the invention is to create an ultrasonic echo measuring device which is constructed as economically as possible, works trouble-free and is easy to use. An object of the invention is therefore seen primarily in significantly improving known devices.

A device for imaging ultrasound, which is applied to a body for diagnosis and which is partially reflected back as an echo, with an electroacoustic transducer according to the invention consists of a plurality of elements of the transducer, which are arranged in concentric rings one inside the other in one plane. Such an electroacoustic transducer is advantageously used simultaneously for emitting the ultrasonic waves and for receiving the reflected ultrasonic waves. The device also has a large number of register units, preferably analog counters of the so-called “CCD” type (charge transport storage register). Each register is coupled to a converter element. A clock pulse generator is connected to each register and generates signals with a first clock frequency. Furthermore, a large number of further clock pulse generators are provided, which are also connected to the analog memories. The second type of clock generator delivers clocks with different predetermined clock frequency. In addition, time-dependent clocks are provided which control the operation of the first and second clocks, so that alternately one memory is loaded with one frequency and the other memory is read out with the other frequency at the same time. Finally, an electrical connection is provided for transporting the read signals to an imaging system.

In the present invention, the delay line required for each converter element is replaced by a predetermined frequency of the second clock generator. With the respective clock frequency, a line is read into a memory with a corresponding delay. By delaying the clock frequency read frequency can be read from the memory with a common frequency for all segments.

Another embodiment of the invention is seen in the fact that, contrary to the reading method described so far, the memories are loaded with a common frequency and the delay required for each segment is only taken into account when reading out with a different frequency. In addition, when reading in and reading out the clock frequency, it can be matched to the respective segment.

• Figur 1 ein Gerät der Erfindung im Einsatz,
• Figur 2 im Querschnitt einen Meßkopf des Gerätes mit einem Blockschaltbild der zugehörigen Auswertelektronik,
• Figur 3 einen Teil der elektrischen Schaltung in Blockform, der zur Anpassung des dynamischen Br.ennpunktes vorgesehen ist,
• Figuren 4 A und B zur Darstellung hilfreiche Funktionen der Schaltung aus Figur 3,
• Figur 5 ein Blockschaltbild einer anderen Schaltung für die Erfindung,
• Figuren 6 A und B die zugehörigen Funktionen zur Erklärung des dynamischen Brennpunktes für Schaltung von Figur 5,
• Figur 7 eine weitere Ausführung der elektrischen Schaltung in Blockform,
• Figur 8 eine zum Verständnis geeignete graphische Darstellung.

Further advantageous embodiments of the inventions are described below with reference to the schematically illustrated drawing. Show it

• 1 shows a device of the invention in use,
• FIG. 2 shows in cross section a measuring head of the device with a block diagram of the associated evaluation electronics,
• FIG. 3 shows part of the electrical circuit in block form, which is provided for adapting the dynamic combustion point,
• FIGS. 4 A and B to illustrate helpful functions of the circuit from FIG. 3,
• FIG. 5 shows a block diagram of another circuit for the invention,
• FIGS. 6 A and B the associated functions for explaining the dynamic focus for the circuit of FIG. 5,
• FIG. 7 shows a further embodiment of the electrical circuit in block form,
• Figure 8 is a graphical representation suitable for understanding.

In Figure 1, the outer dimensions of a scanning device according to the invention are shown in comparison with an object. The Control panel 10 includes a screen 11, such as a cathode ray tube, in a suitable front panel. A video tape recorder or other memory can also be used

e.g. B. on the basis of photographic signals (screen copier), contained in the control panel 10 to provide the signals for displaying an image. Furthermore, the control panel 10 contains a power supply and parts of the circuit for generating time-dependent frequency and for driving the scanner in the Measuring head 50. The measuring head 50 (or probe) is connected to the control panel 10 with an electrical line 48. The measuring head 50 of the present exemplary embodiment is essentially cylindrical in shape and has, in the vicinity of one end, a scanning window 51 which, for example, is made of resilient material such as. Silicone rubber. In order to handle the device, the measuring head 50 is brought into a position to be held by the operator, so that the scanning window 51 is directed towards the object to be scanned. In the case of the object shown in FIG. 1, for example, the area around the heart of a People are scanned. Of course, the probe can also be used to measure other parts of the body or other objects to which it should be directed with a handle.

According to FIG. 2, the probe 50 is shown in cross section, to which associated parts of the evaluation electronics are connected, which can be arranged partly in the probe 50 and partly in the control panel 10. The housing of the measuring head 50 includes a front sound guiding chamber 52, which contains a liquid, and a rear sound measuring chamber 53; which contains part of the electronics. Both chambers 52 and 53 have a cylindrical shape with the same diameter, so that they can be assembled into a cylinder with the aid of a tube 54 which has an annular extension 55 on its outside. The (inner) tube 54 carries a flat-shaped sound generator 80 and a sound collecting lens 90, of which the. the two housing parts are separated from one another (cf. US Pat. No. 3,958,559). The scanning window 51 is located at the end of the chamber 52. Around the window opening an approach is provided on which an elastically resilient membrane 56, for example silicone rubber membrane, is fitted. The front sound chamber 52 is filled with a liquid 57, for example water. The membrane 56 should be so elastic that it lies smoothly with the measuring head on the surface of the body to be measured in order to keep disturbing reflections of sound waves at a transition between the liquid of the device to the object as low as possible.

A flat, e.g. Metallic, sound-reflecting scanning device 70 is arranged in the liquid 57 between the sound lens 90 and the scanning window 51. Of course, the surface of the non-arched scanner can be curved and focus or scatter even reflected sound waves. The scanning device 70 (sound mirror) is fastened to an axis 71 which is perpendicular to the plane of the drawing and which can be passed through the housing wall of the front sound guide chamber 52 in order to be operated from the outside by a small electric motor 72 which generates the reciprocating movement . A torque transmitter 73, which is also fastened on the axis of rotation of the sound mirror and on the housing 52, has been particularly highlighted in FIG. 2.

Like the outer parts of the electric motor, the torque transmitter 73 shown in dashed lines can be accommodated in another housing part (not shown). The sound generator (exciter) 80 is connected directly to an electrically operated sound generator or sound receiver 130, from which sound-stimulating pulses alternate and sound echo pulses coming back are received at the sound sensor 80. It is not shown that various electrical devices known per se for concentrating the ultrasound beam can be provided between the acoustic exciter 80 and the electrical exciter 130.

For dynamic focusing. for example with step lenses, our US patent Ser. No. 665,898 (U.S. Patent No.).

The electroacoustic transducer 80 is divided into a plurality of segments which lie in concentric rings around a central element in one plane. In the illustration, only three segments, designated 81, 82 and 83, are shown instead of a confusing variety. Of course, the electroacoustic transducer has many more segments. The segments of the electroacoustic transducer 81-83 are connected to an electrical pulse generator 120, from which they can be excited in a known manner to emit ultrasound. The transducer elements are also connected to the new circuit for dynamically adjusting the focus according to the invention.

The circuit designated 130 works only when sound waves are received and forwards electrical signals in accordance with the reflected echo signals of the ultrasound for the purpose of being displayed on a screen. Pre-amplifications and amplifiers, which are not shown in detail in the figure, may also be present in this circuit. The output of the circuit 130 for the dynamic adjustment of the focal point is connected to a screen 11 and a further receiver which is used for storing the television picture by means of a video device. A particularly advantageous circuit for amplifier control is described in more detail in US Pat. No. 4,043,181 (US Ser. No. 569,185). Such an amplifier control is intended to filter out echo signals which arise outside the measuring range.

The timing generator 170 is provided to generate pulses at equal intervals with which the system is synchronized; the pulses of the timing generator 170 become the pulse generator 120 and the dynamic pulse receiver 130 alternately and in addition from the scanning drive and the circuit for deflecting the electron beam 180, so that pulsed ultrasonic pulses are emitted and received alternately and that the movement of the mirror drive and the vertical and horizontal deflection of the electron beam of the cathode ray tube 11 are coordinated.

The circuit generally works as follows: A carrier signal from the time-constant clock generator 170, conducted via the connection 178, excites the pulse generator 120 to generate pulses that are transmitted to the segments of the electroacoustic transducer 80. As is known, concentric ring segments of ultrasound transducers are excited to align an ultrasound beam with a focal point via delay lines. A further beam alignment is possible through the lens 90. The ultrasound beam introduced into the body to be examined via the scanning mirror 70, the area of which is shown in the figure by dotted lines, is partially recognized as an echo after the sound has been emitted by the subsequent switchover of the device to reception. The electroacoustic transducer 80 now converts the echo signals reflected back via the scanning mirror into electrical impulses in the opposite direction.

The electrical signals are made visible on a screen 11 by the switching module 130. The screen shows a section in the direction of the ultrasonic wave sent through the object, so-called B scanning direction. The second dimension of the image is the swivel range of the ultrasound wave, which is obtained by slowly moving the scanning mirror 70 back in the direction of the double-sided arrow 7.

FIG. 3 shows a block diagram of the electrical circuit for dynamic beam alignment for the switching module 130, which is connected to the segments of the ultrasonic transducer 80. A memory 131-133 is connected to each segment 81-83. The memories are preferably components that operate analogously as so-called CCD components. The output of this memory is applied to an adder 147, the output of which is at the input of gate 148. The output of gate 148 is connected to screen 11 via a filter 149, from which impressed clock pulses are probed.

Clock generators 141, 142 and 143 are each assigned to a sound converter 81-83, on which they generate clocks with which information is fed into the registers 131-133. The clock generator 141 generates a predetermined frequency F ₀ , the clock generator 142 a predetermined frequency F ₀ ⁺ _A F ₁ and the clock generator 143 a predetermined frequency F ₀ + Δ F ₂ . The outputs of the clock generators 141-143 are connected to the corresponding register inputs via AND gates 151, 152 and 153, through which the counting into the memories is controlled. The second input of each AND gate 151-153 is at the output of switch 154. The output of AND gate 151 is connected, in addition to the input of memory 131, to counter 155, which counts pulses with a frequency F ₀ .

In the example of the present invention, each register 131-133 has n memory locations, accordingly the counter 155 counts up to the number n at a maximum. When the counter 155 has counted n pulses, it resets its counter to 0 and closes the switch 154, which of the Time generator 170 is controlled. The counting signal described in this way can advantageously be used to switch the device from transmission to reception. The clock frequency of the time-dependent clock generator 170 is also set such that only echo waves in the intended measuring range are received.

A pulse generator 135 provides pulses of frequency F _C which are connected to each memory 131-133 and after which the information is read from the memories. Of the. Output of generator 135 is connected to the memories via gate 139. The gate 139, which is also connected to a counter 136, which counts a maximum of m digits, sets the counter 136 to 0 when the maximum permissible pulses m are reached, closes the switch 137 and exchanges the mode of operation of the device from reception to storage via the Switch 155, in which the switch 137 sets the AND gate 139 and the AND gate 148 in the shifted switching position.

• Nach einem Signal des Zeitgenerators 170 öffnet sich der Schalter 154, der seinerseits die Gatter 151 - 153 öffnet. Somit können elektrische Signale von den elektroakustischen Wandlern 81 - 83 in den Speichern 131 - 133 mit der jeweils vorgewählten Taktrate der Taktgeneratoren 141 - 143 eingelesen werden, bis m Takte, die vom Zähler 155 mitgezählt werden, gespeichert sind. Der Speicher 131 wird dabei mit der niedrigen Frequenz F_O aufgefüllt, bis der Zähler 155 m Takte gezählt hat, nach denen er sich selbst auf 0 setzt, den Schalter 154 schließt und den Schalter 137 öffnet. Der Schalter 154 schließt auch die Gatter 151 - 153 und beendet somit den Speichervorgang, dem nun durch den Schalter 137 ausgelöst, das Auslesen folgt, indem die Gatter 139 und 138 geöffnet werden. Die Information aus den Speichern 131 - 133 gelangt über Addierer 147 und Gatter 148, sowie Filter 149 _- auf den Bildschirm 11. Von dem Filter 149 werden aufgeprägte Taktfrequenzen wieder entfernt. Das Auslesen wird mit einem Zähler 136 kontrolliert, der die beim Auszählen aufgeprägten Impulse vom Impulsgenerator'135 bis zu einer Zahl maximal m zählt, wobei n zeitgleich m gesetzt wird, wonach der Zähler 136 den Schalter 137 wieder schließt und Gatter 139 und 148 wieder öffnet.

The circuit 130 shown in detail in FIG. 3 operates on the whole as follows:

• After a signal from the time generator 170, the switch 154 opens, which in turn opens the gates 151-153. Electrical signals from the electroacoustic transducers 81-83 can thus be read into the memories 131-133 at the respectively preselected clock rate of the clock generators 141-143 until m clocks, which are counted by the counter 155, are stored. The memory 131 is filled with the low frequency F ₀ until the counter has counted 155 m cycles, after which it sets itself to 0, closes the switch 154 and opens the switch 137. The switch 154 also closes the gates 151-153 and thus ends the storage process, which is now triggered by the switch 137 and is followed by the reading by opening the gates 139 and 138. The information from the memories 131-133 arrives on the screen 11 via adders 147 and gates 148, and also filters 149- _. Imprinted clock frequencies are removed from the filter 149 again. The reading is controlled with a counter 136 which counts the impulses impressed during the counting from the pulse generator '135 to a maximum number of m, n being set at the same time m, after which the counter 136 closes the switch 137 again and opens gates 139 and 148 again .

A delay in the ultrasound pulses is therefore only simulated after receipt in that the signals supplied by the ultrasound transducer are read in with a higher clock frequency increasing towards the edge of the transducer. This compensates for the path difference from the edge visible from FIGS. 4 A and B. The difference in the respective clock frequency is doubled by a corresponding readout process. When using the frequencies F ₀ , F ₀ + Δ F ₁ and F ₀ + Δ F ₂ , the difference to the central converter element is n times Δ T ₁ and n times Δ T ₂ (where F = 1: T). The delay is therefore set directly by the clock generators 141-143.

Since the difference in the delay depends on the penetration depth (cf. FIGS. 4 A and β, in which measurement at different focal points Z a to Z c'd is shown), the difference in the delay of the adjacent transducer elements must be set inversely to the penetration depth. Part of the delay is taken over by the focusing lens 90 (FIG. 2), which, however, should not be greater than the minimum delay at the maximum penetration depth. The known ultrasound devices were not suitable for penetration depths beyond this. If measuring devices with an arbitrarily large penetration depth are to be developed, then the focusing lens 90 would first have to be dispensed with.

FIG. 4 A shows an arrangement approximately in the order of magnitude of a device to be built, from which it can be seen that sound waves from the intended focal point Z a to the first ring take 2.5 msec and to the second receiver ring 5.0 msec longer than to the center . If the depth of penetration is greater, the difference is that the ultrasonic waves from the focal point to the outer receiver zones require correspondingly less.

If one assumes that the memories 131-133 are designed with 1000 memory locations and that the counter 155 counts to the number 1000, if one continues from a clock frequency F ₀ = 20 megahertz with a shift Δ F ₁ of 1.05 megahertz and ΔF ₂ = 2.22 megahertz, then the clock generators 141 - 143 deliver pulses with a frequency of 20 megahertz, 21.5 megahertz and 22.22 megahertz.

In this example, the device is set as follows: The timing generator 170 is set to a signal which is recorded in the shortest time from point Z a in segment 81. The clock-wise storage of the signals in the memories 131-133 now lasts 50 µsec., Which corresponds to exactly 1000 clocks at a 20 megahertz frequency. The counter. 155 counts these 1000 clocks exactly until the memory is completely filled, so that echo information from the focal point Z a is available in the last filled-up memory location. The clock periods of the clock generators 142 and 143 last 47.5 and 45 microseconds. The external ultrasound transducers are thus divided into smaller storage locations, so they receive more timing pulses after the same reception time, so that the information from the focal point is also stored in the last storage location. However, the smaller the storage clock frequency, the greater the distance to the corresponding information of the neighboring converters. In this way, the focus is shifted electrically adjustable.

The electrical shift of the focal point, which is predetermined by different clocking, is of course only visible when the memories are read out again at a uniform frequency. A shift can be emphasized even more clearly if the same delay is clocked out in reverse order. In terms of circuitry, this is very simple because a control required for this purpose is already provided for recording and storing the signals.

FIG. 4B shows the course of the ultrasound waves from focal points Z b and Z c which are further away, with a path length of 40 μsec. the difference to the outer receivers 82 and 83 on 0.5 and 1µsec. has shrunk. This, smaller path difference is compensated for by a correspondingly smaller cycle number difference.

A particularly advantageous device of the invention is seen in the fact that components for setting the number of cycles of each register are operably connected by a common drive shaft in such a way that they simultaneously determine the number of cycles in proportion to the distance between the focal point and in relation to the change in the number of cycles of the adjacent memories. Such an adjustment can also be done in stages.

In a further embodiment of the invention, an electrical circuit with corresponding block symbols is shown in FIG. 5, in which the corresponding components are provided with reference numerals that differ from the reference numerals in FIG. 3 by a 2 in the hundreds if they fulfill corresponding tasks.

• Nach einem Signal des Zeitgenerators 170 öffnet.sich der Schalter 254, der seinerseits die Gatter 251 - 253 öffnet. Somit können elektrische Signale von den elektroakustischen Wandlern 81 - 83 in den Speichern 231 - 233 mit der jeweils vorgewählten Taktrate der Taktgeneratoren 241 - 243 eingelesen werden, bis n Takte, die vom Zähler 255 mitgezählt werden, gespeichert sind. Der Speicher 231 wird dabei mit der niedrigen Frequenz F₀ aufgefüllt, bis der Zähler 255 n Takte gezählt hat, nach denen er sich selbst auf 0 setzt, den Schalter 254 schließt und den Schalter 237 öffnet. Der Schalter 254 schließt auch die Gatter 251 - 253 und beendet somit den Speichervorgang, dem nun durch den Schalter 237 ausgelöst, das Auslesen folgt, indem die Gatter 239 und 238 geöffnet werden. Die Information aus den Speichern 231 - 233 gelangt über Addierer 247 und Gatter 248, sowie Filter 249 auf den Bildschirm 11. Von dem Filter 249 werden aufgeprägte Taktfrequenzen wieder entfernt. Das Auslesen wird mit einem Zähler 236 kontrolliert, der die beim Auszählen aufgeprägten Impulse vom Impulsgenerator 235 bis zu einer Zahl maximal n zählt, wobei n zeitgleich m gesetzt wird, wonach der Zähler 236 den Schalter 237 und Gatter 239 und 238 wieder schließt.

The circuit 130 shown in detail in FIG. 5 generally works as follows:

• After a signal from the time generator 170, the switch 254 opens, which in turn opens the gates 251-253. Thus electrical signals from the electroacoustic transducers 81-83 can be read into the memories 231-233 with the respectively preselected clock rate of the clock generators 241-243 until n clocks, which are counted by the counter 255, are stored. The memory 231 is filled with the low frequency F ₀ until the counter 255 has counted n clocks, after which it sets itself to 0, closes switch 254 and opens switch 237. The switch 254 also closes the gates 251-253 and thus ends the storage process, which is now triggered by the switch 237 and is followed by the reading by opening the gates 239 and 238. The information from the memories 231-233 reaches the screen 11 via adder 247 and gate 248, as well as filter 249. Imprinted clock frequencies are removed again from the filter 249. The reading is controlled by a counter 236, which counts the impulses impressed during counting from the pulse generator 235 up to a maximum number of n, n being set at the same time m, after which the counter 236 closes the switch 237 and gates 239 and 238 again.

The electrical circuit according to FIG. 5 differs from that described in FIG. 3 by delay elements 201 and 202 on the direct connection of the electroacoustic transducers 81-83 to the pulse generator and to the receivers. These delay elements 201 and 202 (D ₁ , D ₂ ) the variable focal point is set without much change in the clock numbers of the clock generators 241-243. This is particularly advantageous when an ultrasound device with variable focal point setting, which also has problems with aspherical optics such as electromagnetic waves, is given a further possibility of variation. Finally, it must be expected that the propagation speed of ultrasound waves of an ultrasound band, however narrow it may be, is different, which can lead to inaccuracies in the measurement result.

The mode of operation of a circuit according to FIG. 5 is explained in more detail with reference to FIGS. 6 A and B. FIG. 6A shows a cross section of a measurement with a relatively close focal point Zq, while in FIG. 6B one further away lying focus Zr is shown. The delay elements 201 and 202 (or D ₁ and D ₂ ) electrically compensate the specification with which the ultrasound waves arrive in the central segment 81 rather than in the outer segment 83.

FIG. 7 shows how the progressive change in the clock frequency of elements of the sound transducer from the inside out can be used simultaneously for the input and removal of the memories. Since errors in the own system could have a particularly unpleasant effect in this case because they double, the delay elements D and D ₂ , with which the variable focus can also be corrected, are particularly important. A counter 336 is used in common, which is always in operation and always counts the number of cycles of the information read. The present circuit differs from that described above by a component 355, a so-called flip-flop, which, depending on the excitation, jumps from one stable position to another stable position. Such and similar simplifications of the electrical circuit are particularly important for a device when the receiver alone consists of many individual parts, so that the evaluation electronics shown, for example, only on three receiving parts does not become complicated and uneconomical to produce.

The drive for the scanning mirror 70 is also controlled by such a circuit. This is to ensure that a swept scanning area is sonicated and searched evenly. A compromise must be found between the natural frequency that is naturally permissible in the water for the recording frequency of the memories.

Reference numerals

Claims (13)

1. Device for imaging a body, characterized in that a device (12 ₀ ) for delivering energy to a body is provided that a converter (80) is provided for converting the energy reflected by the body into electrical signals, which in at least two parts (81, 83) are divided, that at least two memories (131, 132) are provided, the inputs of which are each connected to an output of an energy converter (31, 82), that at least two pulse generators (141, 142) are provided, each one Memory are assigned, and generate the pulses with different distances, that an electrical circuit is provided for sorting the pulses that are directed into the respective memory or taken from the memory and that a device _' (147) for combining the from the Save read signals is provided for visual representation. 2. Device according to claim 1, characterized in that ultrasonic energy is used. 3. Device according to claim 2, characterized in that the energy converter (80) consists of a central part and at least one part lying concentrically thereto in one plane (32, 83). 4. Device according to claim 3, characterized in that the second pulse generator (141), which is assigned to the converter concentrically around the central part, generates pulses with a higher frequency than the pulses for the central element (81). 5. Device according to claim 2, characterized in that a controller (155) for the mutual operation of the clock generators (141, 142) and associated memory (131, ...) is provided for mutual reading and reading. 6. Device according to claim 4, characterized in that a controller (155) for the mutual operation of the clock generators (141, 142) and associated memory (131, ...) is provided for mutual reading and reading. 7. Device according to claim 5, characterized in that the memories (131, ...) are analog charge transport memories (CCD). 8. Device according to claim 1-7, characterized in that a first pulse generator (135) is provided for all memories. 9. A method of operating a device according to any one of the preceding claims, characterized in that for imaging a body by the energy reflected by it, which has been introduced into it, with a transducer unit consisting of at least two parts, in which a focus according to the following Steps are set that an energy converter element is assigned to each memory, that the signals received by converters are divided into pulses of different lengths, that the pulses are stored and that the stored pulses are converted into signals for image display. 10. The method according to claim 8, characterized in that the memories are read at different frequencies. 11. The method according to claim 8, characterized in that the received signals are modulated with the dividing pulse frequency. 12. The method according to claim 10, characterized in that the signals are modulated when storing and reading out. 13. The method according to any one of the preceding claims, characterized in that a living body is searched for defects.

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