WO2010057480A2

WO2010057480A2 - Method and device for measuring fluid flow

Info

Publication number: WO2010057480A2
Application number: PCT/DE2009/001642
Authority: WO
Inventors: Udo Steppe; Andreas Dahlke; Michael Teufel
Original assignee: Nivus Gmbh
Priority date: 2008-11-20
Filing date: 2009-11-20
Publication date: 2010-05-27
Also published as: DE102008058376A1; WO2010057480A9; WO2010057480A3; DE112009003438A5

Abstract

The invention relates to a method for determining fluid flows, wherein ultrasonic impulses are radiated into the fluid in alternating directions by means of an ultrasonic phase array, and impulse responses from different directions are analyzed for determining a fluid flow. The total flow through the cross section of the fluid bed guiding the fluid is thereby determined by means of cross-correlation from the ultrasonic impulses from flow speeds for given volumes present in different directions, considering said cross section and considering the fluid bed walls and/or the presence or absence of sediments.

Description

Title: Method and apparatus for fluid flow measurement

description

The present invention relates to the determination of fluid flows.

There are a variety of applications where it is desirable to be able to accurately grasp fluid flows. This includes, for example, the measurement of waste water volumes that flow through open or closed channels, the measurement of water flowing through a body of water, etc.

It has already been proposed to perform flow measurements using ultrasonic sensors.

For example, DE 197 40 549 A1 describes a method for measuring the flow characteristic of a medium in open channels, in which ultrasound pulses are radiated into a fluid and received from the latter, whereby the desired flow characteristics are determined by cross-correlations. Other documents dealing with flow measurements, for example, DE 40 16 529 Cl, which relates to a flow meter for open channels, DE 195 42 232 Al, which relates to an ultrasonic flowmeter liquid or gaseous media, DE 44 43 483 Al, the DE 40 27 030 Al, which relates to a method and an apparatus for measuring the flow rate, DE 33 14 260 Al, which is a device for measuring the per unit time by a

- X - With regard to open-channel fluid flow, DE 32 23 393 A1, which relates to a method and apparatus for determining the flow rate in liquids, FR 2 710 979 A1, which relates to an arrangement for measuring flow at fluctuating water levels, GB No. 2,029,030 A1, which relates to a fluid flow meter, US Pat. No. 5,821,427, which relates to a fluid velocity measuring arrangement using curve adaptation of peak speed detection, and US Pat. No. 5,315,880 relating to a method for measuring a fluid velocity by determining the Doppler frequency shift of microwave signals. An open trench flow meter is known from JP 57101720 A, an apparatus for measuring physical quantities of a liquid with two ultrasonic wave transducers is known from DE 2 703 439 B2, a method or apparatus for determining the flow volume in a duct is omitted DE 198 57 572 Al known and DE 196 50 621 Al relates to a measuring device for detecting the flow rate. DE 196 49 931 A1 relates to a device and a method for measuring a flow rate. Reference is also made to DE 101 34 264 B4 of the applicant of the present invention. It should be noted that from the cited documents, such as DE 195 42 232 A1, correlation methods and the like for the evaluation of ultrasonic impulse responses are known and that such methods are therefore assumed to be known per se in the present case.

From US-PS 5,521,833 a method for determining the three-dimensional velocity of a fluid such as air or water is known, wherein signals of certain frequencies in at least three different directions by means of a planar Transmitter arrays are transmitted and the transducers are used to receive backscattered acoustic signals from the fluid, wherein signal trains at different frequencies determined first in a first direction, then in a second direction certain direction and finally emitted in a third specific direction and subsequently all backscattered by the fluid Signals are recorded. The maximum measuring range should be extended in this way.

From DE 10 2007 001 057 Al a device for radioacoustic remote measurement of at least two components of a flow velocity vector is known. In this case, for the height-resolved remote sensing of wind speeds and directions electromagnetic waves to be reflected back into the medium irradiated sound waves. This technique is known as RASS, radioacoustic probing system. The sound waves are to be generated by means of an array.

Regardless of the multitude of documents dealing with the measurement of fluids, including the use of ultrasonic pulses, it is desirable to further improve the fluid flow measurement. Thus, the measurement of fluid flows should also be possible for a less experienced user; it should be accurate, especially when the fluid is flowing over varying amounts of sediment or the like, and / or the ultrasonic sensors are subject to fluctuations in position due to turbulence, waves or the like, etc. It would be desirable to provide at least some of these problems with at least partial relief , The object of the invention is to provide new products for commercial use.

The solution to this problem is claimed in an independent form. Preferred embodiments can be found in the subclaims.

The present invention thus proposes, in a first basic idea, a method for determining fluid flows in which ultrasound pulses are radiated into the fluid and a fluid flow is detected on the basis of the impulse responses. It is preferred that the irradiation direction is changed by means of an ultrasound phase array and the fluid flow is detected by impulse responses from different directions.

It should be mentioned that it is not only possible but preferable to measure fluid flows in the limited cross-section of an open tube or narrow channel, such as a restricted channel or a flowing, narrow body of, for example, a maximum of 10 m, preferably a maximum of 5 m width , Wall effects are particularly strong here. These can be taken into account by specifying a known cross section; However, it is preferred if the cross section is determined with the UIt- raschallarray itself. This reduces the complexity of the device and thus simplifies the application, especially in unknown cross-section of the fluidized bed.

The spatially resolved measurement of velocities is also preferred since turbulence is determined by the determination of velocity fields or turbulence models are used in the determination of the total flow can. Such turbulence models need not necessarily use general assumptions such as the compelling, complete correctness of the Navier-Stokes equations due to practical deviations. This makes it possible to perform fast, accurate measurements thanks to cross-correlation determinations.

The direction of irradiation of the ultrasound pulses can be changed very quickly by the use of ultrasound phase arrays without mechanical adjustment and therefore in particular. This allows significantly improved measurements. Thus, either additionally the movement of the ultrasonic sensor can be detected, for example by means of a separate acceleration sensor, in order then to compensate for the detected movement and thus to allow a measurement in always the same direction. This already improves the measurements without requiring active intervention by a user. Alternatively and / or additionally, it is possible to acquire a more exact value by measuring in different directions and averaging or integration. Again, this is possible without intervention of a user in an automated manner.

The assembly is usable with a variety of different fluids. Thus, the fluid may be a gas or gas mixture, in particular natural gas and / or methane, and / or a liquid, in particular water and / or aqueous solutions and / or suspensions, in particular pure water, drinking water, waste water; however, it is also possible to measure chemicals, for example industrial process chemicals. Since it is possible to measure in different directions, as a result of which the accuracy is increased, a measurement can take place, in particular despite the presence of turbulences. Fluid flows can be detected according to the invention in a variety of different conditions and applications. However, the measurement in open waters, open channels, pipelines and in particular pressure lines will be particularly relevant.

It will be appreciated that the distance in which ambient fluid flows are readily measurable as the respective ultrasonic phased array will depend on the ultrasound pulse power, the quality of the electronics used in ultrasonic array excitation and pulse evaluation, and so on. If the fluid flow is determined at a distance of three to five, preferably a maximum of ten meters, this is sufficient for a large number of applications and does not require much equipment. This is particularly advantageous for measurements on open channels on the mainland.

The ultrasound pulses will typically be injected into the fluid at a frequency of over 200 kHz and below 4,000 kHz, preferably around 1,000 kHz with a bandwidth of +200 - 500 kHz. These frequencies can be generated easily. The preferred frequency range also makes it possible to change the frequencies that are radiated into the fluid. This is advantageous because it is preferred if the ultrasound pulses are radiated into the fluid at frequencies varying over time, in particular with a frequency deviation of more than a few hundred kHz, preferably around 400 to 1000 kHz, assuming sufficiently high fundamental frequencies. In this case, the ultrasonic pulse frequencies can be changed abruptly and / or chirpedly. This brings significant advantages in the evaluation.

It should be noted that the emission direction in phase arrays depends on the frequency of the emitted pulses. When "chirping", ie the tuning of the frequency during a single pulse, the emission lobe will thus migrate and can be compensated for, either by adjusting, ie changing, the phase position of different elements of the ultrasonic phase array during tuning / or, by taking into account in the evaluation that the pulse signal responses come from changing directions, since the dependence of the emission direction on the emission frequency for a given ultrasound phase array is readily determinable, the compensation is problem-free, that is to say in particular without a complicated intervention It should be pointed out that chirped tuning is possible both continuously and in small, in particular quasi-continuous steps.

The direction of irradiation is preferably changed abruptly. This is preferred over a gradual sweep of a region. Thus, according to the invention, it is not necessary to scan two directions lying next to one another, but instead it is possible to scan directions which differ more from one another. This is advantageous because in this way adjacent directions are scanned at different times, which on the one hand allows better compensation for sensor movements and Ensures an improved measurement even with turbulence in the flow. Thus, by "jumping" the direction, the differences in the flow velocity at different points can be detected very well, that is, flow vectors can be measured particularly easily and well.It is possible to use a certain step pattern, with which all or almost All directions are scanned, repeated over again or to vary the pattern itself over time, so that errors are better avoided by periodic disturbances.

It should be noted that it is possible to determine the density of ultrasound-scattering particles or the like in the fluid or to determine the fluid composition from the ultrasound-scattering or absorbing particles or the like using the method according to the invention. Since it is known for many fluids, such as waste water or oil mixtures, which particle load is associated with which chemical load or composition, appropriate conclusions can be drawn about the chemical composition of the fluid. In particular, for example, a solids content in water, in particular wastewater can be determined.

An ultrasonic phase array has a plurality of linearly or, preferably, two-dimensionally arranged ultrasound emitting and / or receiving elements. It is preferred if all elements of the ultrasonic phase array are amplified as equally as possible. It is not necessary that when amplifying the received signals all the elements of the ultrasonic phase array equal gain factors are assigned, but that the gain of the individual Elements are selected so that all elements produce the same output under otherwise identical conditions. This is advantageous, for example, for digitizing the signals in order to be able to carry out a signal evaluation while carrying out cross-correlation.

It is possible that a flow profile is generated and / or turbulence is detected by irradiation of ultrasound pulses in different directions-and the evaluation of the impulse responses obtained for this purpose. This increases the accuracy of the measurements that are performed. It should be noted that the ultrasonic phase array may be one-dimensional, that is, a line array is usable; in such a case, a fan-like sweep of a layer can take place. With a second line array, which is, for example, designed to be complementary, velocity vectors can be determined in the entire flow cross section. Typically, however, two-dimensional arrays of ultrasound transmitters / receivers will be used. Here, flow patterns can be detected three-dimensionally without mechanical movement of the sensor field and thus particularly well determine turbulence, etc. If correlation measurements are carried out, it is advantageous to adapt evaluation windows taking into account determined turbulences and / or flow profiles. This makes it possible to reduce the evaluation windows in the course of a continuous measurement and thus to increase the evaluation time and the repetition frequency or sampling rate. It should be mentioned that the evaluation windows can not only be reduced automatically, but can also be enlarged in the same way. It is possible to detect the signal background and to take it into account in the signal evaluation. For this purpose, for example, a measurement without prior emission of ultrasonic signals. The signals obtained thereby represent a background to be subtracted, for example, by means of which the measurement accuracy can be further increased.

It is possible and preferred when sediments are detected by the method of the present invention. In this way, due to deposits in pipelines, bodies of water, etc., contraction of the cross-section can be taken into account, which at the same flow rate causes a reduction in the total flow rate. The detection of sediments thus contributes to increasing the accuracy of measurement further.

It is possible to also use the impulse responses or the flow data determined during their analysis to determine fixed marks and / or to determine the position of the ultrasound phase array. So the location of sediments will not change in the short term. If, for example, a sensor floating on the surface of a fluid rocks, it will lead to a supposed movement of the sediments; but since such will not occur, it can be concluded that the sensor has moved, which can be compensated. The high measuring rate, with which it is possible to scan in different directions, advantageously allows comparatively fast movements to be detected. It should be noted, however, that if necessary, an accelerometer or the like can also be integrated into the sensor or its housing in order to avoid loading. compensate for movements of the same. The integration can be done for example by installation on a carrier board or the like or done by integration on one and the same chip.

Furthermore, protection is also claimed for a fluid flow measuring arrangement, in particular for the implementation according to one of the previously described methods with an ultrasound pulse transmitting / receiving means for transmitting ultrasound pulses in fluids and for receiving ultrasonic pulse responses from the fluid and an evaluation means for Determination of fluid flows for the evaluation of the ultrasonic impulse responses. It is preferred that the ultrasound pulse transmitting / receiving means is designed as a two-dimensional ultrasound array and the evaluation means for evaluating impulse responses from different directions. The ultrasonic pulse transmitting means will typically be a multi-dimensional ultrasonic phase array.

The invention will be described in the following by way of example only with reference to the drawing, wherein is shown by

1 shows a measuring arrangement of the present invention during a measurement.

Referring to Fig. 1, a fluid flow measuring assembly 1, generally designated 1, includes ultrasonic pulse transmitting / receiving means 2 for transmitting ultrasonic pulses 3 in fluids 4 and for receiving ultrasonic pulse responses from the fluid and an evaluation means 5 for determining

Fluid flows for evaluation of the ultrasonic impulse responses, wherein the ultrasonic pulse transmitting / receiving means 2 as

- II - Ultrasonic array is formed and the evaluation means for evaluating impulse responses from different directions. 6

In the present case, the fluid flow measuring arrangement 1 is used for measuring quantities of fluid which flow through a fluid bed. In principle, the fluid flow meter assembly is adapted to be used with a plurality of fluid beds; in the figures, the bed of an open channel in which the sensor of the fluid flow measuring arrangement 1 floats is shown as fluid bed 4a. The fluid flow measuring arrangement for this purpose comprises for the ultrasonic pulse transmitting / receiving means 2 a suitable, fluid-tight housing and a connection leading away therefrom. Although this connection may be wireless if desired; in such a case, the sensor housing will be provided with a suitable power supply. It should be noted that an evaluation or preliminary evaluation at the ultrasonic pulse transmitting / receiving means 2 is preferred and this can form together with corresponding circuits, etc., a co-enveloped sensor, whereby, if necessary, only one

Transmission of fluid flow data, for example, as a total flow data is required. If desired, it is also possible for the data to be recorded and a reading to be made after completion of a measurement and connection to a suitable interface.

However, it is preferred, typical and illustrated that the sensor in its fluid-tight housing comprises only one signal conditioning 7, for example a gain of the signals received with the individual ultrasound phase array elements, a linking stage and a digitization and then the digitized data for one further evaluation fed via a multicore conductor 8 to a sufficiently powerful central processing unit, which serves as evaluation means 5, in which the data are linked together in order to obtain fluid flow-indicative values from the (digitized) impulse responses received from the different directions determine. In this way, at the same time the driving of the sensor can be prevented. In addition to the signal generation and conditioning but also the entire further evaluation can be done in the sensor, the driving of the sensor can then be prevented, for example, with the power / voltage supply.

The ultrasound pulse transmitting / receiving means 2 for transmitting ultrasound pulses 3 in the present case is designed as a two-dimensional array of ultrasound emitting and receiving elements. Associated with the array is a frequency generator (not shown) which generates an adjustable ultrasonic frequency, for example between 800 and 1200 kHz in the illustrated embodiment. The frequency generator permits the change, and thus also the tunability, of the frequency generated during the pulse, that is to say it chirps by a frequency which can be predetermined by a controller. Each element of the array is connected to the frequency generator via a programmable phase shifter (not shown) and an amplifier. The

Phase shifters are programmable by a controller (not shown) with which the relative phase angle of two elements relative to one another can be set so precisely that when the ultrasound waves emitted from all elements are superimposed, an emission in the liquid results in a desired direction. It should be pointed out that in the case of chirping impulses - that is, that during an im- Pulses the radiated frequency changes - and constant setting of the phase shifter will change the direction of the irradiation of ultrasonic pulses. This change in direction will generally be small, and since the corresponding chirp frequency directional relationship is known or determinable for a given array, it can be compensated for. The amplification of the ultrasonic frequency generated by the generator is sufficient to excite the individual elements so strongly that a sufficiently strong ultrasonic pulse is emitted into the fluid.

The ultrasound pulses 3 pass through the fluid 4. In this case, they are subject to absorption by the fluid and the particles 9 therein, as well as to a Doppler shift. From the emitted ultrasound pulses, ultrasonic impulse responses are returned to the sensor, where they are received by the elements of the ultrasound phase array.

The fluids 4 are in the illustrated embodiment effluents in open channels, here for example in sewage treatment plants, where they are fed through the open channels clarifier.

The evaluation means 5 comprises a computer for evaluating the impulse responses received from the sensor and conditioned there. The evaluation means 5 is designed to determine the flow velocity in volumes which lie along the respectively illuminated direction; it is further designed to conclude, based on the determined flow velocities of volumes, on the presence of turbulences in the detected fluid volume, evaluation windows taking into account to adjust the instantaneous or typically present turbulence and to determine the total flow through a cross-section of the fluid bed by integrating the flow rate over the individual volumes. Furthermore, the evaluation means is designed to take into account the presence of sediments, that is, a zero-flow, high-reflectance, zero-flow area without the need to provide information about the fluid bed geometry.

The controller in the sensor is designed to effect an emission in different directions 6 by appropriate settings of the phase shifter and to receive 6 impulse responses from these directions. In this case, the directions do not change as per se also possible by fan-like sweeping, but spaced points are illuminated on a plane, as shown in Figure 1 on the basis of the respective main axis of the successively emitted ultrasonic beam lobes characterizing lines 6a - see 6f; that the control is designed so that all points of a given projection surface 10 are illuminated gradually, will be obvious.

The arrangement is used as follows:

First, the fluid-tight and buoyant coated sensor is spent in the fluid, which can be done by inserting the sensor already connected to the evaluation. Due to the evaluation line, the sensor is prevented from driving off at the same time. Then the control is activated and chirping pulses are generated in the frequency generator. At the same time, the phase shifters assigned to the individual elements are adjusted such that a first emission direction results for a center frequency. The pulse generation is continued for a certain duration - the pulse duration - and during this time the elements of the ultrasonic phase array are subjected to ultrasound power, the frequency of the ultrasonic waves being determined by the respective frequency at the frequency generator and the relative phase position relative to one another by the phase shifters. that emission (for a given center frequency) results in a desired direction, for example 6a.

After expiration of the pulse duration of the frequency generator is then turned off and the power application of the elements terminated. At the same time, the signal which is now present at the elements is started to be conditioned, ie amplified and digitized, as an impulse response signal. The digitized signal is then transmitted to the evaluation means with further information, for example regarding the respectively illuminated direction.

After expiration of an impulse response time, a new phase adjustment is made to the phase shifters and ultrasound irradiation in another direction, for example 6b, is performed as previously described. The other direction is chosen so that different points are illuminated on a projection surface around the sensor, but it is possible to determine differential speeds from the volumes IIa, IIb lying in different directions 6a, 6b. In this way, all directions that are to be achieved with the sensor are scanned step by step.

Furthermore, scanning is carried out regularly in different directions 6c to 6f without pulses having previously been emitted. This makes it possible to subtract the signal background, which is caused, for example, by the inherent noise of elements and the signal conditioning electronics.

It will be appreciated that optionally a separate signal background can be determined for each direction, allowing for best fit, but reducing the sampling rate because of the increased time for signal background measurements. Alternatively, it would be possible to make only a few measurements in different directions and, if necessary, to perform interpolation between the signal ground of different directions. This can already be helpful to consider local differences. Even easier is the consideration of the signal background, if only a single signal background measurement is made globally for all directions. Which type of underground determination makes the most sense in each case will depend, among other things, on the behavior of the ground. Thus, with pronounced directional stability, that is, at least largely isotropic background, but at the same time strong temporal variability, it will be preferable to consider the signal background globally, but to record it frequently. If, on the other hand, a large directional dependence is given, but which is largely constant over time, occasional detection of the background in different directions may be preferred. It is important It may be pointed out that the background behavior may in turn be influenced by a large number of factors, such as possible temperature fluctuations of the fluid, interference, etc. That the background consideration can be changed during the course of a measurement, for example because the background stabilizes over time, but changes in direction instead occur, should be mentioned.

From the impulse responses which are received for a respective direction, flow velocities for given volumes are then determined in per se known manner in the evaluation unit taking into account the possibly weighted direction-interpolated signal background. It can be concluded on the basis of those volumes which have a zero flow velocity and are particularly far from the sensor, on the presence of deposits, that is, sediments and the like. From the position of a surface, which is spanned by these volumes, it can then be deduced whether the sensor has moved or not. In this case, a possible swinging motion can be compensated for at a sufficiently high sampling rate by carrying out a rotation transformation around the sensor in such a way that a constant, typical average position of the sediment surface results. It is worth mentioning that a fluid bed wall can be used as a fix flat in the absence of sediments. Likewise, other transformations may be mentioned in order to compensate, for example, for translational movements about a central position.

Moreover, it is possible to optionally determine a rocking frequency and recorded at different times during a scan signals to different Way to compensate. This is particularly advantageous in sudden changes of directions.

After the optionally performed and preferred, although not mandatory, compensation for the background signals and the fluctuations, a flow pattern can be established and the total flow through a cross section of the fluidized bed can be determined. In particular, differential speeds of different volumes and thus velocity vectors in the liquid can also be determined.

In this way, an increased accuracy in the measurement is possible.

Claims

claims

1. A method for determining fluid flows, in which ultrasonic pulses are irradiated by means of an ultrasonic phase array in changing directions in the fluid and

Pulse responses are evaluated from different directions to determine a fluid flow, characterized in that from the ultrasonic pulses, taking into account the cross section of a fluid-carrying fluid bed and taking into account the Fluidbettwandung and / or the presence or absence of sediments of the total flow through this cross section of flow velocities for given volumes in different directions is determined by cross-correlation.

2. Method according to the preceding claim, characterized in that on the basis of those volumes which have a flow velocity of zero or near zero and optionally particularly far from the sensor, the presence of sediments, Fluidbettwandungen and the like closed and preferably also the cross section of the liquid-conducting fluid bed is determined.

3. Method according to the preceding claim, characterized in that it is deduced from the position of a surface which is spanned by a flow velocity of zero or near zero and preferably at the same time particularly far from the sensor, whether the sensor has moved ,

4. A method for determining fluid bed flows according to one of the preceding claims, characterized in that for determining the total flow through a cross section of the fluid bed determines a flow pattern and / or determines a flow velocity vector or a plurality of flow vectors and / or a flow velocity as a difference of at different Determining certain flow velocities is determined, in particular with sudden change of the direction of irradiation for those directions between which each jumps, and / or a flow profile is created and / or turbulence detected and / or information about turbulence in the flow and / or the flow contour and or dead zones are used for window reduction in correlation measurements and / or sedimentations are detected, and / or an analysis of determined flow data and / or impulse responses for the determination of fixed marks and / or for determining the position of the ultrasonic phase array is made.

5. The method according to any one of the preceding claims, character- ized in that the fluid flow is detected at a distance of three to five, preferably a maximum of ten meters, preferably in one of open waters, open channels, pipelines, in particular pressure lines.

6. A method for determining fluid flows according to any one of the preceding claims, characterized that the fluid is one of the group of gases, in particular natural gas and / or methane, and / or liquids, in particular water and / or aqueous solutions and / or suspensions, in particular pure water, drinking water, waste water and / or chemicals that

Density of ultrasound-scattering particles or the like is determined in the fluid, wherein preferably closed by evaluating the density of the ultrasound-scattering particles and / or the like on a chemical composition of the fluid.

7. A method for determining fluid flows according to one of the preceding claims, characterized in that ultrasonic pulses having a frequency of about 200 kHz and / or below 4,000 kHz, preferably around 1,000 kHz with a bandwidth of ± 200 - 500 kHz in the fluid are irradiated and / or ultrasound pulses are irradiated with varying over time frequencies in the fluid, in particular with a frequency of over some 100 kHz, preferably around 400 - 1 000 kHz, preferably the ultrasonic pulse frequencies are changed abruptly and / or chirp-like and / or is compensated for the migration of the ultrasonic emission lobe with variation of the frequency of the ultrasound pulses emitted into the fluid.

8. A method for determining fluid flows according to one of the preceding claims, characterized in that the irradiation direction is changed abruptly.

9. A method for determining fluid flows according to one of the preceding claims, characterized in that All elements of the ultrasonic phase array are amplified as equally as possible and / or the signal background is detected and taken into account in the signal evaluation.

10. A method for determining fluid flows according to any one of the preceding claims, wherein the ultrasonic 1-phase array is used for ultrasonic pulse irradiation, preferably transmitting and receiving.

11. Fluidströmungsmessanordnung, in particular for execution according to one of the preceding method claims with a Ultraschallimpulsende- / receiving means for transmitting ultrasonic pulses in fluids and for receiving ultrasonic impulse responses from fluids and an evaluation means for determining fluid flows for evaluation of the ultrasonic impulse responses, characterized in that Ultrasonic pulse transmitting / receiving means is designed as an ultrasound laser array and the evaluation means for evaluating impulse responses from different directions.