EP2643747A2

EP2643747A2 - System for detecting and locating a disturbance in a medium, and corresponding method and computer program

Info

Publication number: EP2643747A2
Application number: EP11831834.4A
Authority: EP
Inventors: Jean-Pierre Nikolovski
Original assignee: Commissariat a lEnergie Atomique CEA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2010-11-23
Filing date: 2011-10-27
Publication date: 2013-10-02
Also published as: US20130233080A1; FR2967788A1; US9417217B2; WO2012069722A3; WO2012069722A2; JP2013544356A; FR2967788B1

Abstract

The invention relates to a system comprising: means (304, 306) for emitting successive acoustic waves in a medium (102); means (308) for receiving successive acoustic waves following propagation in the medium (102), designed to supply a reception signal from the successive acoustic waves received; and means for detecting and locating the disturbance in the medium on the basis of the reception signal. At at least one particular frequency, the phase and/or amplitude spectrum of each acoustic wave has an amplitude, or phase respectively, varying in the medium according to a particular spatial distribution in terms of amplitude, or phase respectively, and the emission means (304, 306) are designed such that the spatial distributions in terms of amplitude, or phase respectively, of successive acoustic waves are different from one another.

Description

System for detecting and locating a perturbation of a medium, corresponding method and computer program

The present invention relates to a system for detecting and locating a perturbation of a medium, a method and a corresponding computer program.

It is known from the state of the art different systems for detecting and locating a disturbance of a medium, comprising means for emitting successive acoustic waves in the medium, means for receiving successive acoustic waves after their propagation in the medium, designed to provide a reception signal from the successive acoustic waves received, and means for detecting and locating the disturbance in the medium from the reception signal.

US Pat. No. 6,741,237 B1 describes a system using the disturbance of a transit time of seismic acoustic waves propagating in an object between an emitting transducer and at least two receiving transducers arranged around the object so that the disturbance caused by the touch generates different fluctuations in the transit time from the touch zone to the two receiving transducers. This system is based solely on transit time differences and requires the transducers to be placed in precise locations around the object to maximize the transit time differentials in at least two distinct directions, for example in the corners for a plate rectangular.

FR 07 03651 discloses a system using the relative absorption signature recognition of a seismic acoustic wave, on a set of resonant figures of the interface object. The relative damping and phase shift for each frequency induced by a touch is one of the components of a relative damping vector built on a predefined number of resonant figures. Nevertheless, this system has the disadvantage of having the sensors in places of the object to break the axis of symmetry of the object so as to obtain good location reliability. In addition, the resonant figures can easily be disturbed by the mounting conditions of the interface in its support and a fortiori if the plate can slide in a slideway that is to say if the boundary conditions are not fixed. .

US Pat. No. 6,396,484 B1 describes a system using the transit time measurement of surface seismic acoustic waves, damped by contact with the finger. This system is characterized by a precise path that an acoustic wave must travel through a known time interval and at a fixed frequency typically of a few megahertz. The position of the touch is correlated with attenuation of the signal at a precise instant depending on the path traveled by the wave imposed by partial reflectors arranged in directions perpendicular to the edges of a rectangular plate. This system has the drawback of requiring the object to be physically etched so as to generate an array of partial reflectors of the surface wave traveling through the object. The paths traveled by the wave are therefore fixed and known.

It may thus be desirable to provide a system for detecting and locating a disturbance of a medium that makes it possible to overcome at least some of the aforementioned problems and constraints.

The subject of the invention is therefore a system for detecting and locating a disturbance of a medium, comprising:

means for emitting successive acoustic waves in the medium,

means for receiving successive acoustic waves after their propagation in the medium, designed to provide a reception signal from the successive acoustic waves received, and

means for detecting and locating the disturbance in the medium from the reception signal,

the transmitting means being designed so that the amplitude and / or phase spectrum of each acoustic wave having, at at least a certain frequency, an amplitude, or a phase, varying in the medium according to a certain spatial distribution of amplitude, respectively of phase, these spatial distributions of amplitude, respectively of phase, successive acoustic waves are different from each other.

Thanks to the present invention, the disturbance of the medium causes a variation of acoustic waves successively received by the receiving device, and therefore a variation of the reception signal. However, this variation depends on the spatial distribution of amplitude or phase of the acoustic waves. Since the transmission means emit the acoustic waves having successively different spatial distributions, the system of the invention makes it possible to obtain, for the same disturbance, several successive variations (one by spatial distribution) in the reception signal. Each of these variations is a characteristic of the disturbance. Having enough features, that is to say enough different spatial distributions, it is possible to detect and locate this disturbance.

Thus, it is no longer necessary to provide acoustic waveguides or use transit time calculations.

Optionally, the transmission means comprise:

an emission device comprising first and second acoustic wave sources respectively having first and second radiation patterns, concentric and different from one another,

means for modifying the relative weighting of the amplitudes of the acoustic waves of the first and second sources, the successive weightings respectively corresponding to the successive spatial distributions.

Also optionally, each radiation pattern has an axis in the direction of which it is zero, the axes forming a non-zero angle between them.

Optionally also:

each source of acoustic waves comprises two elements of piezoelectric transduction,

the transmission means comprise means for polarizing the two piezoelectric transduction elements with two potentials opposite each other.

Also optionally, the transmission device comprises a piezoelectric element coupled to the medium and four electrodes covering a respective quarter of a face of the piezoelectric element, the two transduction elements of the first source respectively comprising two opposite electrodes. to one another and the two transducing elements of the second source respectively comprising the two other electrodes opposite to each other.

Optionally also:

the medium comprises a plate having a contact surface,

the acoustic waves are seismic acoustic waves propagating in the plate,

the disturbance is a contact on the contact surface.

Optionally also:

the medium comprises a fluid on the surface of a plate, the acoustic waves are acoustic waves of compression propagating in the fluid on the surface of the plate,

the disturbance is the presence of an impedance break at the surface of the plate, for example caused by the presence of an obstacle.

Optionally also, the piezoelectric element comprises a sleeve designed to emit acoustic compression waves.

The invention also relates to a method for detecting and locating a disturbance of a medium, comprising:

providing control signals to an acoustic wave emission device, so that said emission device emits successive acoustic waves in the medium,

receiving a reception signal from an acoustic wave receiving device receiving the successive acoustic waves after their propagation in the medium,

detecting and locating the disturbance in the medium from the reception signal,

characterized in that

the control signals are designed so that the amplitude and / or phase spectrum of each acoustic wave having, at at least a certain frequency, an amplitude, respectively a phase, varying in the medium according to a certain spatial distribution of amplitude, respectively of phase, these spatial distributions of amplitude, respectively of phase, successive acoustic waves are different from each other.

Optionally,

the control signals are intermittently supplied so that the average exposure power, even in the ultrasound range, remains below 85 dB, with a reference of 2.10-5 Pa, in the air at one centimeter from the device acoustic wave emission,

the control signals have a certain frequency band of excitation,

and the method further comprises, before detecting and locating the disturbance in the medium from the reception signal:

amplifying the reception signal and converting it by means of an analog-digital converter, the amplification being configured so that the amplitude of the signal received in the absence of disturbance reaches the full quantization scale of the analog-digital converter,

- Perform a band-pass filtering of the reception signal, on a frequency band corresponding to the excitation frequency band.

Finally, the invention also relates to a computer program downloadable from a communication network and / or recorded on a computer readable medium and / or executable by a processor, characterized in that it comprises instructions for the performing the steps of a method for detecting and locating a disturbance of a medium according to the invention, when said program is executed on a computer.

The invention will be better understood with the aid of the description which follows, given solely by way of example and with reference to the appended drawings in which:

FIG. 1 is a three-dimensional view of a first tactile surface system embodying the invention,

FIG. 2 is a sectional view of the tactile surface system of FIG. 1;

FIG. 3 is a front view of a glass plate of the system of FIG. 1,

FIG. 4 is a diagram showing acoustic wave transmission and reception devices and a computing device of the tactile surface system of FIG. 1,

FIG. 5 is a view from above of the transmission device of FIG. 4, on which a first source of acoustic waves is indicated,

FIG. 6 is a directivity diagram of the first acoustic wave source of FIG. 5,

FIG. 7 is a view from above of the transmission device of FIG. 4, on which a second source of acoustic waves is indicated,

FIG. 8 is a directivity diagram of the second acoustic wave source of FIG. 7,

FIGS. 9 to 13 are theoretical and experimental directivity diagrams of the transmission device of FIG. 4 according to different relative contributions of the two sources, FIG. 14 is a graph illustrating two control signals provided by the computing device respectively to the two sources of the transmission device of FIG. 4;

FIG. 15 is a front view of the glass plate of FIG. 3, on which reference contacts are indicated,

FIG. 16 is a block diagram of a learning method,

FIG. 17 is a block diagram of a monitoring method,

FIG. 18 is a three-dimensional view of a second tactile surface system embodying the invention,

FIG. 19 is a sectional view of a contactless interface system embodying the invention,

FIG. 20 is a sectional view of a resonator disk of the system of FIG. 19,

FIG. 21 is a view from above of the resonator disc of FIG. 20,

FIG. 22 is a curve showing the amplitude of vibration of a sleeve perpendicular to its axis of symmetry, when the resonator disk of FIGS. 20 and 21 is biased,

FIG. 23 is a sectional view of an interface system with and without contact embodying the invention,

FIG. 24 is a set of three curves showing the principle of a detection of several simultaneous disturbances,

FIGS. 25 and 26 show directivity diagrams of the transmission device of FIG. 4 according to different phase shifts between the two sources, and

FIG. 27 represents a sectional view of an improvement of the interface system of FIG. 23.

Referring to Figure 1, a touch surface system 100 according to an exemplary embodiment of the invention comprises first a glass plate 102 having two opposite faces 104A, 104B.

The glass plate 102 may have dimensions up to 1.8 meters high, 0.7 meters wide and 8 millimeters thick. It may be monolithic, tempered or laminated glass, for example type 442, that is to say four millimeters of glass, two millimeters of interlayer PVB (polyvinyl butyral) and again four millimeters of glass. The touch surface system 100 further includes a pedestal 106 for holding the glass plate 102 in a vertical position. The glass plate 102 is inserted in the base 106 by a lower edge, while its other three edges can remain bare.

Referring to Figure 2, the base 106 defines a slot 202 in which a lower portion 204 of the glass plate 102 is introduced and maintained by a frame 206, wedges 208 and a bead 210. A seal to stuff 212 ensures sealing at the opening of the slot 202.

With reference to FIG. 3, the touch surface system 100 further comprises two emission devices 304, 306 of seismic acoustic waves in the plate 102 and a reception device 308 of the seismic acoustic waves, the three devices being fixed, for example by gluing, in the inner part 204 of the glass plate 102.

Preferably, the three devices 304, 306, 308 are aligned along the lower edge of the glass plate 102.

In addition, in order to eliminate any ambiguity of contact location, the reception device 308 is preferably located between the two transmission devices 304, 306. However, it is also possible to arrange the two transmission devices 304, 306. on the same side of the receiving device 308.

In addition, the emission devices 304, 306 are preferably arranged at the ends of the lower edge of the glass plate 102.

Two notches 310, 312 are formed in this lower edge, the notches extending between the receiving device 308 and respectively each transmission device 304, 306, in order to limit the direct coupling between each transmission device 304, 306 and the receiving device 308. Preferably, the notches 310, 312 do not extend beyond the transmitting devices 304, 306 and receiving devices 308.

The transmitting devices 304, 306 and receiving devices 308 are attached indifferently to one side or the other of the glass plate 102.

Preferably, the acoustic waves emitted and received are bending waves having a long wavelength in front of the thickness of the glass plate 102. These are volume waves. The energy of the acoustic field of these waves is distributed over the entire thickness of the glass plate 102.

If the glass plate 102 is homogeneous and isotropic, the system 100 is preferably designed to detect contacts on the two contact surfaces 104A, 1 04B, independently of the contact surface 1 04A or 1 04B where are fixed the emission devices 304, 306 and 308 receiving devices.

With reference to FIG. 4, the first transmission device 304 comprises a piezoelectric disk 402 (that is to say in piezoelectric material) having a lower face covered with a lower electrode 404 by which the first transmission device 304 is pressed against the glass plate 1 02. The piezoelectric disk 402 further has an upper face covered with four upper electrodes 406A, 406B and 408A, 408B, each covering a respective quarter of the upper face. In the example described, the piezoelectric disk 402 is polarized uniformly over its entire surface.

The second transmitting device 306 is identical to the first transmitting device and likewise comprises a piezoelectric disk 410 provided with four upper electrodes 41 2A, 412B and 414A, 414B on its upper face and a lower electrode 41. on its underside.

The receiving device 308 comprises a piezoelectric disk 41 8 having a lower face covered with a lower electrode 420 pressed against the glass plate 1 02. It further comprises an upper face covered with an upper electrode 422.

The touch surface system 1 00 further comprises a computing device 424 connected to the electrodes of the transmitting devices 304, 306 and receiving devices 308.

More specifically, the lower electrodes 404, 416, 420 of the two transmitting devices 304, 306 and the receiving device 308 are connected to an electrical ground of the computing device 424. In addition, the computing device 424 is designed to provide the signals. subsequent commands to the first transmitting device: (t) between the two opposite electrodes 406A, 406B, and e ₂ (t) between the two other opposite electrodes 408A, 408B. In the example described, the two opposite electrodes are polarized respectively between two e (t) e (t)

potentials opposed to each other: ^{and + ~} ^ ' ^and ' ^{es it} ' ^{them other} electrodes e (t) opposed between respectively two potentials opposite one another: ^and , e ₂ (t) The upper electrode 422 of the receiving device 308 is connected to the computing device 424 to provide it with a reception signal r (t), from the acoustic waves received by the reception device 308.

The computing device 424 is also designed to provide control signals to the second transmitting device 306, in the same manner as for the first transmitting device 304, so that they will not be detailed hereinafter.

The computing device 424 is designed to detect and locate a contact on one of the contact surfaces 104A, 104B from the reception signal r (t) corresponding to the received seismic acoustic waves, that is to say to the acoustic waves seismic emitted by the first and second emission devices 304, 306 and propagated in the glass plate 102.

For this purpose, the computing device 424 is designed to implement the actions which will be detailed with reference to FIGS. 16 and 17.

For example, the computing device 424 includes a processing unit (not shown) for executing instructions of a computer program (not shown) to implement these actions.

As a variant, the computing device 424 could be replaced by an electronic device consisting solely of electronic circuits (without a computer program) for carrying out the same actions.

The notions of radiation pattern and directivity will be used later.

A radiation pattern of an acoustic wave source corresponds to the amplitude modulus of the acoustic waves at each point of a predetermined sphere centered on the source, divided by the maximum amplitude modulus along the sphere. Thus, the values of the directivity diagram are between zero and one.

A directivity diagram corresponds to the intersection of the radiation pattern with a plane. It therefore characterizes the amplitude modulus variations on a circle of the plane centered on the source.

With reference to FIG. 5, the two opposite electrodes 406A, 406B are aligned along an axis A1 passing through the center of the piezoelectric disk 402. These two electrodes 406A, 406B form a first dipole source of acoustic waves (vibrating dipole radiating a minimum acoustic field, for example zero, along an axis A2 passing through the center of the piezoelectric disk 402 and different from the axis A1, the acoustic field being antisymmetric with respect to this axis A2 (same absolute value, but opposite signs, that is to say opposition of phase).

Thus, with reference to FIG. 6, the first dipolar acoustic wave source has a first directivity pattern on the contact surface 104A or 104B, around the center of the piezoelectric disk 402, with a minimum value, zero in the example described, along the axis A2 passing through the center of the piezoelectric disk 402.

In the example described, the axis A2 is perpendicular to the axis A1. Preferably, the axes A1 and A2 are oriented one perpendicular to the lower edge of the object and the other parallel to the same edge.

In the example described, the directivity diagram of the source 406A, 406B has an "8" shape, and a zero value in the direction of the A2 axis. For example the first directivity diagram, noted Vl _dir , is equal to

Vl _dir = with an angle from I axis A1.

With reference to FIG. 7, in the same manner as the electrodes 406A, 406B, the two opposite electrodes 408A, 408B are aligned along the axis A2 and form a second dipolar source of acoustic waves (vibrating dipole) radiating a acoustic field zero along the axis A1 and antisymmetric with respect to the axis A1 (same absolute value, but opposite signs, that is to say in opposition of phase).

Thus, with reference to FIG. 8, the second dipolar acoustic wave source has a second directivity pattern on the contact surface 104A or 104B, around the center of the piezoelectric disk 402, having a minimum value, zero in the example described, along the axis A1.

In the example described, the directivity diagram of the source 408A, 408B has a shape in "∞", with a zero value in the direction of the axis A1. For example, the second directivity diagram, denoted V2 _djr , is equal to

V2 _dir = with an angle from I axis A1.

max V sin ² a + sin ² 2a

at

Thus, each acoustic wave source is designed to emit, that is to say radiate, acoustic waves into the glass plate 102 according to its respective directivity diagram, the two directivity patterns being concentric and different from each other. the other. The control signals generate, by an inverse piezoelectric effect, acoustic waves in the glass plate 102, in particular antisymmetrical Lamb waves characterized by their two displacement components, in the plane of the plate and out of plane (perpendicular to the plane of the plate ). The disturbance caused by a touch with the glass plate 102 essentially affects, by damping or blocking the contact surface, the out-of-plane displacement component (i.e., perpendicular to the glass plate 102).

In polar coordinates, the out-of-plane component of the acoustic field, denoted S ₁ , emitted by the first acoustic wave source 406A, 406B and observed at a distance r from the center of the piezoelectric disk 402 and at an angle α, is similar to the signal control unit ^ (t) of the acoustic wave source 406A, 406B

2n

with, on the other hand, a propagation delay-r, or A denotes the length

AT

acoustic waves, and on the other hand a weighting corresponding to the directivity diagram. In the example described, the control signal ^ (t) is sinusoidal e _i (t) = E sm _l0 (2nft), so that the out of plane component S _t is also sinusoidal and described by its components coordinates

Cartesian with respect to axes A1 and A2: cos () .A _w . sini 2 .fi - r

where A ₁₀ designates sin (2a) .A ₁₀ sini 2n.fi - r the peak amplitude of the out-of-plane component S _l , proportional to the peak amplitude of the control signal E _l0 .

Similarly, in the example described, the control signal e ₂ (t) is sinusoidal e ₂ (t) = E ₂₀ sin (2nft), so that the out of plane component of the acoustic field, denoted S ₂ , due to the second acoustic wave source 408A,

408B, is also sinusoidal and described by its components <! In Cartesian coordinates with respect to axes A1 and A2: S ₂ (t, r,) = where A ^L 20 designates

the peak amplitude of the out-of-plane component S ₂ , proportional to the peak amplitude of the control signal E ₂₀ .

The out-of-plane displacement components S ₁ and S ₂ (i.e. perpendicular to the glass plate 102) of the acoustic fields both correspond to bending modes and are therefore sensitive to contact, for example to that of a finger on the glass plate 102.

The computing device 424 is designed to weight the two control signals ((t) and e ₂ (t) and to vary this weighting over time. In the example described, the weighting is carried out as follows: ke ^ t) and

(l - k) .e ₂ (t) with k varying between zero and one. This weighting variation causes a corresponding variation in the amplitudes of the acoustic fields S ₁ and S ₂ :

At _l = kA and A ₂ = (l - k) .A ₀ , so that:

The two sources 406A, 406B and 408A, 408B are excited independently of each other, each of them generating a characteristic field of the geometry and orientation of the electrodes.

The inverse piezoelectric excitation of elastic waves is a linear and invariant process, so that the out-of-plane component of the total acoustic field generated by the first transmission device 304 is equal to the sum of the out-of-plane components of the two sources. : S (t, r,) = S ₁ (t, r,) + S ₂ (t, r,) = either: r - φ r - φ

,

The first transmission device 304 thus generates acoustic waves whose spatial amplitude distribution at any frequency / varies as a function of k.

To illustrate this variation, in the case where the two sources of acoustic waves are controlled in phase with a phase shift φ zero and synchronously, that is to say at the same frequency, the total out-of-plane component S can be expressing according to a module and a phase, ie, in complex notation:

S (t, r, a) = _T J (k cos (ar) .A _10. (1 - k). Sin (2a) .A ₂₀ f + (k, sin (2a) A ₁₀ . k) sin (a) .A ₂₀ ) ² .e ^

Thus, the out-of-plane component of the acoustic field emitted at the frequency / by the first transmission device 304 is written in a general manner: S {t, M, k) = A (M, k). .f .t - (p (M)), where M is a point on the touch surface 104A having the coordinates r, a. This out-of-plane component has an amplitude distribution A (M, k) at the frequency f, which varies as a function of k. This means that for two different values of k, the associated amplitude distributions are different and not proportional to each other.

In the case of the first transmission device, these amplitude distributions are all angular since A (M, k) depends in fact only on the angle.

To illustrate this variation of the amplitude distribution, various forms of the directivity diagram, according to the preceding equations and if necessary obtained experimentally, of the first transmission device 304 according to different values of k are illustrated in FIGS. 9 to 13. For the experimental results, a PZ26 piezoelectric disk 30 mm in diameter and 0.5 mm in thickness was glued on a borosilicate plate of dimensions: 360 mm × 220 mm × 3.3 mm. The velocity vector was measured on an 80 mm radius circle centered on the piezoelectric disk. The frequency of the signal was / = 40 400 Hz. In the example described, the touch surface system 100 further comprises the second transmission device 306. As for the first transmission device 304, the out-of-plane component of the acoustic field S '(t, M, k ) at the frequency / emitted by the second transmitting device 306 is written in a general manner: S '(t, M, k) = A' (M, k) .nu (2π. / 1 - φ '(M )).

Thus, the out-of-plane component of the total field, at frequency /, has the same form: S _totd (t, M, k) = A _total (M - φ _ίοία1 (Μ)). According to the invention, the total acoustic field thus has a _total amplitude distribution A (M, k) at the frequency /, which varies as a function of k. This means that for two different values of k, the associated amplitude distributions are different and not proportional to each other.

If the acoustic waves emitted are not monochromatic (that is to say at a single frequency) Fourier's theory returns to the monochromatic case, by decomposing any signal into a sum of monochromatic signals.

With reference to FIG. 14, in the example described, the computing device 424 is designed to grow from zero to one in forty steps and to decrease the frequency / from one step to the next, from 100 kHz to 20 kHz. It is interesting to decrease the frequencies rather than the opposite, because the high frequency acoustic waves propagate faster than the acoustic waves of lower frequency. Thus, by decreasing the frequencies, it is avoided that the first acoustic waves emitted are caught by the following.

Thus, the first control signal is, for the plateau i (i ranging from one to forty): e _l (t) = k _i .A ₀ sm (2qf _i t), while the second control signal is, for this same step i: e ₂ (t) = (1 - sin (2 ^ t), with fc _x = 0, k ₄₀ = 1 and f _l = 100 kHz, ₄₀ = 20 kHz.

Preferably, each step lasts for a whole number of periods of oscillation of the control signals ((t) and e ₂ (t).

Thus, at each step, the first transmission device 304 emits an acoustic wave at the frequency f and with an amplitude distribution:

A (M, k _t ) = Thus, the amplitude spectrum of each acoustic wave i is non-zero for the single frequency f The amplitude spectrum of each acoustic wave therefore has, at this frequency f _t , different in the example described of an acoustic wave emitted to the other, an amplitude varying in the medium according to a certain spatial distribution of amplitude A (M, k _t ). Thanks to the variation of k _i from one acoustic wave emitted to the other, the spatial distributions of amplitude AM, k _i ) successive acoustic waves are different from each other.

Methods of learning and monitoring will now be described which utilize these variations of spatial distributions.

With reference to FIG. 15, these methods use reference contacts C (i, j) whose positions on the contact surface 104B of the glass plate 102 are known to the computing device 424. These reference contacts C (i , j) are for example distributed on a grid along the axes A1 and A2, where the indices indicate their position in the grid.

These methods also use a neighborhood function V (c (i, j)) for determining the neighboring reference contacts of a given reference contact C (i, j). For example, in the case where the reference contacts are distributed on a rectangular grid, the neighboring reference contacts are the eight contacts surrounding the reference contact considered on the grid ("first ring"), as shown in FIG. 1 5.

Moreover, in these methods, only the first transmission device 304 will be considered, since the introduction of the other transmission device 306 does not change, as explained above, the general expression of the total acoustic field in the plate.

With reference to FIG. 16, the training method 1600 firstly comprises a step 1602 in which the touch surface system 100 is placed in a quiet environment while the glass plate 102 is left without contact.

Under these conditions, during a step 1 604, the computing device 424 supplies the control signals e t) and e ₂ (t) as represented in FIG. 14 to the first transmission device 304, and this last emits acoustic waves in the glass plate 102. At the same time, during a step 1606, the receiving device 308 receives the acoustic waves after their propagation in the glass plate 102, and supplies the computing device 424 with a vacuum reception signal, denoted r (t). corresponding to the acoustic waves received. The empty reception signal r (t) lasts during all the successive spatial distributions.

During a step 1608, the computing device 424 calculates the amplitude of the Fourier transform of the vacuum reception signal r (t), called the empty spectral amplitude R {f) = .

During a step 1610, a reference contact C (i, j) is applied to the contact surface 104A of the glass plate 102, again in a quiet environment.

During a step 1612, with the reference contact C (i, j) applied, the computing device 424 supplies the control signals ^ (t) and e ₂ (t) to the first transmission device 304.

During a step 1614, the first transmission device 304 emits acoustic waves corresponding to the control signals ((t) and e ₂ (t) in the glass plate 102, while the receiving device 308, at the During a step 1616, receives the acoustic waves after their propagation in the glass plate 102, and provides the computing device 424 the corresponding reception signal, called reference reception signal r _{; j} (t).

During a step 1618, the computing device calculates the amplitude of the Fourier transform of the reference reception signal r _u (t), called the reference spectral amplitude R _i (f) = ■

During a step 1620, the computing device 424 calculates a distance, called the reference spectral amplitude distance DNR (i, j), between the empty amplitude and the reference amplitude. For example, the reference spectral amplitude distance DNR (i, j) is a relative normalized distance, for example equal to standard 1 of the percentage variation of the empty spectral amplitudes R {f) = Process 1600 then returns to step 1610 for another reference contact C (i, j) until all reference contacts are scanned.

It can be observed that the learning method 1600 needs to be performed only on one of the two contact surfaces 104A, 104B, since two contacts face each other on both sides of the contact plate. glass 102 have the same effect on the acoustic waves propagating in the glass plate 102.

In addition, the Fourier transform of the reception signal is preferably performed on about 16000 points (or at least 4096 points or 1024 points).

Referring to Fig. 17, a monitoring method 1700 using the touch-sensitive surface system 100 first includes initialization steps 1702 through 1712.

During a step 1702, the touch surface system 100 is placed, without any contact being applied to it, in its environment of use, the latter may include a residual noise vibrating the glass plate 102 and producing and a spurious signal in the reception signal provided by the receiving device 306. The residual noise may also come from the processing electronics, including quantization noise.

During a step 1704, the computing device 424 supplies the control signals ^ (t) and e ₂ (t) to the first transmitting device 304, and the transmitting device 304 emits the corresponding acoustic waves into the plate of glass 102.

At the same time, during a step 1706, the receiving device 308 receives the acoustic waves after their propagation in the glass plate 102, and provides the computing device 424 with a reception signal, called a reception signal with residual noise. _BR (t), corresponding to the acoustic waves received.

During a step 1708, the computing device 424 calculates the amplitude of the Fourier transform of the reception signal with residual noise r _BR (t), called spectral amplitude with residual noise R _BR (f) = \ ffi {r _BR {tty.

During a step 1710, the computing device 424 calculates a residual starting noise BRD from the residual noise spectral amplitude R _BR (f) and the empty spectral amplitude R {f). For example the residual noise starting BRD is the norm 1 of the percentage of variation of the spectral amplitudes with residual noise R _BR (f) and empty R (f): BRD = Σ R _B Àf)

R (f)

During a step 1712, the computing device 424 initializes, to the value of the residual residual noise, a data BR representing the residual noise in progress, namely the operation: BR <- BRD. In addition, the computing device 424 initializes an iteration counter n to the value 1, ie the operation: n <- 1.

The monitoring method 1700 then comprises the loop of monitoring steps 1714 to 1750, the current iteration of the step loop being the iteration n.

During a step 1714, the computing device 424 supplies the control signals e ^ t) and e ₂ (t) to the first transmission device 304, and the transmission device 304 emits the corresponding acoustic waves into the plate of glass 102.

At the same time, during a step 1716, the receiving device 308 receives the successive acoustic waves after their propagation in the glass plate 102, and provides the computing device 424 with a reception signal, called a reception signal in progress. _n (t), corresponding to the acoustic waves received.

During a step 1718, the computing device 424 calculates the amplitude of the Fourier transform of the current reception signal r _n (t), called the current spectral amplitude R _n {f) = \ ffi {r _n .

During a step 1720, the computing device 424 calculates a current spectral amplitude distance DNR _n from the spectral amplitudes with residual noise R _BR (f) and current R _n {f). For example, the current spectral amplitude distance DNR _n is a relative normalized distance, for example the standard 1 of the percentage of variation of the spectral amplitudes with residual noise R _BR (f) and current R _n {f): DNR _n = Σ RÀf)

f R _B Àf)

During a step 1722, the computing device 424 calculates a current perturbation PC _n from the current spectral amplitude distance

DNR _n and residual noise BR. For example, the current perturbation PC _n is the percentage of variation between the current spectral amplitude distance DNR _n and the

\ DNR.

residual noise BR: PC "= ^■ 1 xlOO.

BR

During a step 1724, the computing device 424 determines whether the current disturbance PC _n has slightly derived with respect to the previous iteration, which indicates a variation of the residual noise, but not a contact because the latter would cause a large variation of the current disturbance PC _n . This little drift

PC

is for example determined if: x100 <15%.

If a small drift of current perturbation PC _n is determined, the steps

1726 to 1730 are implemented.

During step 1726, the computing device 424 updates the residual noise spectral amplitude R _BR (f) with the value of the current spectral amplitude R _n (f), ie the operation: R _BR (f) R _n (f).

During the step 1728, the computing device 424 calculates the new residual noise BR from the spectral amplitude with residual noise R _BR (f) updated, that is: BR = ^ R _BR (f)

/ R (f)

In step 1730, the computing device 424 increments n by one and the method returns to steps 1714 and 1716.

If no small current disturbance drift PC _n is determined, during a step 1732, the computing device 424 determines whether the current disturbance PC _n is high, for example greater than a predetermined threshold, which would indicate the occurrence of 'a contact. For example, a contact C is detected if:

PC _n ≥ 100%.

If a contact C is detected, during a step 1734, the computing device 424 calculates the differences between the reference spectral amplitude distance DNR (i, j) and the current spectral amplitude distance DNR _n . In the example described, these deviations are relative normalized deviations, for example expressed as percentages of the residual noise. Still in the example described, these differences are placed in an ENRD matrix _n (i, j) where each element of the matrix corresponds to the deviation from the reference contact C (i, j):

DNR _n - DNR (i, j)

ENRD _n (i, j) = 1 ^■ xlOO.

BR

During a step 1736, the computing device 424 determines the reference contact C (i, j) closest to the detected contact C. This is the reference contact associated with the smallest element of the matrix ENRD _n (i, j) (i.e., the element indicating the smallest deviation from the distance d current spectral amplitude DNR _n ). This smallest element is noted

ES _n = ENRD (i _n , j _n ), with (i _n , j _n ) its position in the matrix ENRD _n (i, j) and also in the grid of the reference contacts.

In a simple variant of the invention, the computing device 424 provides as the position of the detected contact C the position of the nearest reference contact C (i _n , j _n ), and the method 1700 then proceeds to step 1750.

However, in the example described, the position of the detected contact C is refined.

Thus, during a step 1738, the computing device 424 determines whether the detected contact C is close to the nearest reference contact C (i _n , j _n ) by means of a proximity condition.

For this purpose, in the example described, this determination is made by calculating a contrast ratio RC _n between the smallest element ES _n and the other elements of the matrix ENRD _n (i, j). For example, the contrast ratio RC _n is calculated by:

(ENR))

Then, the computing device 424 determines whether the detected contact C is close to the nearest reference contact C (i _n , j _n ) from the contrast ratio RC _n . In the example described, the detected contact C is close to the nearest reference contact C (i _n , j _n ) if the contrast ratio is greater than a predetermined value, for example if: RC _n ≥ 150. During a step 1740, if the detected contact is determined as close to the nearest reference contact C (i _n , j _n ), then the computing device 424 provides as the position of the detected contact C the position of the reference contact C (i _n , j _n ) the closest. Process 1700 then proceeds to step 1750.

During a step 1742, if the detected contact is not determined to be close, in the sense of the proximity condition, of the nearest reference contact C (i _n , j _n ), then the computing device 424 determines the position of contact C from the positions of the nearest reference contact C (i _n , j _n ) and its neighboring reference contacts, according to the predetermined neighborhood function V (c (i _n , j _n )).

More specifically, during a step 1744, the computing device 424 calculates an equivalent mass M _n (i, j) for each element of the matrix

ENRD _n (i, j), the equivalent mass M _n (i, j) being all the higher as this element, which corresponds to a deviation from the current spectral amplitude distance DNR _n , is small ( inverse function or equivalent). In the example described, the

ES

equivalent mass M _n (i, j) is calculated by: M _n (i, j) = -, - r.

ENRD _n \ i, j)

During a step 1746, the computing device 424 calculates the barycentre of the reference contacts C (i, j), weighted by their corresponding equivalent weight, located in the neighborhood V (c (i _n , j _n )) around the nearest reference contact C (i _n , j _n ).

During a step 1748, the computing device 424 provides as the position of the detected contact C the centroid thus calculated.

Whether a contact is detected or not at step 1732, in step 1750, the computing device 424 increments n by one and the process returns to steps 1714 and 1716.

It will be noted that, during the monitoring, the control signals are generated with a period of 100 Hz and that the Fourier transforms are carried out continuously on an acquisition window of about 16000 points at a sampling frequency of 1 .6 MS / s (ie 100 Hz) with 12 bit signal quantization. It will further be appreciated that when the touch surface system 100 is designed to detect and locate finger touch, the grid pitch of the reference contacts is preferably less than or equal to the characteristic dimension of the finger. To give an order of magnitude, the contact area of an index is about 1.3 cm ² and the characteristic dimension of the touch is about 12 mm. Thus, the pitch of the grid is preferably less than 1 cm, for example equal to 6 mm. In addition, the learning reference contacts have a characteristic dimension similar to that of a finger. Thus, thanks to the previous grid step, these reference contacts overlap each other. This makes it possible to have a reduced number of reference contacts while offering a high resolution, less than one millimeter, thanks to the calculation of the center of gravity. This further reduces position recognition errors when the touch slips slowly and continuously from one reference contact to another. The fact that there is partial recovery of the reference contacts thus ensures that a touch is more finely localized. Reliability is also increased insofar as a touch is not detected with respect to a single reference contact, but relative to several reference contacts located in the same vicinity. The overlap of two adjacent reference contacts must thus be sufficient so that the disturbances are fairly similar and the calculation of the center of gravity has a meaning. In other words, the grid pitch must be sufficiently fine with respect to the characteristic dimension of the finger so that the random placement of the finger on the tactile zone always sufficiently covers a reference contact. This ensures that the contrast level threshold is always reached during a touch, especially when the touch occurs in the middle of two reference contacts. However, the grid pitch must remain as large as possible so as not to unnecessarily increase the number of reference contacts, and therefore the duration of the learning.

On the other hand, if the gate pitch is much smaller than the characteristic radius of the touch, the neighborhood area can be extended to a second or third reference contact ring. The number of crowns is for example equal to the characteristic radius divided by the grid pitch. For a grid pitch of 3 mm, two crowns of reference contacts will for example be taken.

In a refinement, the position refined through the calculation of the center of gravity can then be recaled to a grid of higher resolution. The position and the displacement of the finger are thus measured rather finely on this grid of higher resolution. For example, the reference contact grid may have a not 6 mm, while the high resolution grid may be that of a graphical display screen typically having a pitch of 0.3 mm. Thus, in the case of an HD screen comprising 1920 x 1080 pixels in the 0.3 mm pitch, or 576 x 324 mm (66 cm or 26 inches diagonal), the grid of the reference contacts is reduced, compared to the grid high resolution, at 97 x 55 or 5335 points, a reduction of almost a factor of 400 while maintaining a fine adjustment of the touch on the high resolution grid.

Furthermore, the method for refining the location of the detected contact can be further improved. Indeed, the method of Figure 17 has the disadvantage that the barycenter as calculated tends to be near the nearest reference contact, even when the detected contact is very "eccentric" of the nearest reference contact that is, almost half way with an adjacent reference contact.

To overcome this problem, the method 17 can be improved to overweight the reference contacts adjacent to the nearest reference contact. This makes it possible to off-center the location of the detected contact with respect to the nearest reference contact, and thus to correctly locate the contacts occurring halfway between two reference contacts. To amplify the effect, it is also possible to define the equivalent masses from the square, the cube or a higher power of the ENRD deviations _n (i, j).

Another way to improve the localization to the mid-distance of two adjacent reference contacts is to determine the position of the contact (detected) from a nonlinear function of the sigmoid or tangent hyperbolic type of the center of gravity relative to at the position of the nearest reference contact. Such a function makes it possible to amplify the small distances of the barycentre with respect to the nearest reference contact, while limiting the position of the contact at the mid-distance. We will take as follows:

, where X _HD , Y _HD are the coordinates of the

Y _HD = Y _zi + t Tanh (a (Y _g - Y _Zi )) detected contact, X _zi , Y _zi the coordinates of the nearest reference contact, X _g , Y _g the centroid coordinates and the amplification factor displacement can be typically between 5 and 10. With reference to FIG. 18, a second touch surface system 1800 according to the invention comprises a rectangular glass plate 1 802 having a periphery 1804.

The touch surface system 1800 further comprises an acoustic wave emitting device 1806 disposed in a corner 1804 of the periphery where two edges 1808, 1810 of the plate 1 802 meet.

The transmitting device 1806 comprises two acoustic wave sources 1812, 1814. The sources 1812, 1814 are elongate and extend respectively along the edges 1808, 1810.

In the example described, the transmission device 1806 comprises a piezoelectric bracket 1 81 6 provided with two arms 1818, 1820, for example rectangular, perpendicular to each other and extending respectively along the two edges 1808. The bracket 1816 has a lower face covered with a lower electrode 1817 and an upper face covered with three upper electrodes: two electrodes 1822, 1824 respectively extending on the two arms and an electrode 1826 extending in the center of the square, at the joint of the two arms. This latter electrode is connected to the lower electrode to form a ground return. The acoustic wave sources comprise respectively the arms 81, 1820 provided with their electrodes.

The touch surface system 1800 further includes an acoustic wave receiving device 822. The receiving device 17828 may be located anywhere on the plate 1802, but preferably away from the transmitter 1806. In the example described, the receiving device 1828 is situated in another corner 1830 of the plate 1802. This makes it possible to reduce the acoustic waves received directly by the reception device 1828 in order to favor those diffracted by a contact on the plate 1802.

The receiving device 1828 comprises a piezoelectric arm 1832, for example rectangular, have a bottom face covered with a lower electrode 1834 and an upper face covered with an upper electrode 1836.

The touch surface system 1800 further comprises a computing device 424 similar to that of the example of FIGS. 1 to 17.

The lower electrodes are thus all connected to the electrical ground, and therefore also to the central electrode 1826. The control signals e t) and e ₂ (t) are applied respectively between the center ground electrode 1826 and the central electrodes 1826. electrodes 1822, 1824 of the arms of the emitting device 1 806. The control signals thus have a single "phase", that is to say a single potential different from the mass. Moreover, the reception signal r (t) is collected between the lower electrode 1834 and the upper electrode 1836 of the reception device 1828.

Alternatively, the upper electrodes 1822, 1824 are each split into two distinct sub-electrodes of equal areas, to which is applied the control signal e ^ t) respectively e ₂ (t). Each control signal then has two "phases", that is to say two different potentials of the mass respectively applied to the two sub-electrodes.

This form of tactile surface system is well suited to small graphic displays, for example seven to ten inches diagonally.

Furthermore, preferably, the emission device 1806 is controlled so as to emit acoustic waves of frequency between one and one hundred kilohertz.

Preferably, the arms 1818, 1820 of the piezoelectric bracket 1816 have a length of several times the wavelength associated with the central frequency of the excitation spectrum of the acoustic waves emitted, for example from two to five times.

Referring to Figure 19, a contactless interface system 1900 according to a possible embodiment of the invention comprises a plate 1902 flat or slightly curved, for example glass, surrounded by air 1903.

The interface system 1900 further comprises a 1904 1906 acoustic wave emission device in the air along the plate 1902.

More specifically, the transmission device 1904 comprises a resonator disc 1908, for example made of metal, having a periphery 1910 and a central portion 1912 tapering from the periphery to the center of the disc 1908, to a central opening. The resonator disc 1908 further comprises a hollow central sleeve 1914 extending perpendicularly to the disc 1908 from the periphery of the central opening, through an opening in the plate 1902. The periphery 1910 of the resonator disc 1902 has a face lower (directed towards the plate 1902) covered with a piezoelectric ring 1915, covered with electrodes in the same manner as the piezoelectric disk 402 of FIG. 4. Thus, the piezoelectric ring has a lower face covered with a lower electrode and an upper face whose quads are covered respectively with four upper electrodes, two of which are visible in FIG. The sleeve 1914 passes through the plate 1902 without touching it and opens out to rise from the plate 1902 by a height preferably of the order of the half wavelength of the acoustic waves propagating in the air, ie 7.5 mm at 23 kHz above the surface (or 3.5 mm at 45 kHz). The sleeve 1914 is closed on the open side through the plate 1902.

The interface system 1900 furthermore comprises a device 1916 for receiving acoustic waves 1906 propagating in the air 1903 along the plate 1902. For better reception of the waves emitted into the air, the receiving device 1916 comprises a resonator disc 1918 similar to the disc 1908, with a piezoelectric ring 1919 covered with a lower electrode and four upper electrodes of the same size as that of the disc 1908, giving it at least the same resonance frequencies, except that It can detect more resonance frequencies by using only one of the signals obtained between one of the four upper electrodes and the ground. The receive signal may also provide a differential signal from two quarters of oppositely opposed electrodes or two half-rings (by joining two quarters of adjacent electrodes) so that its receive spectrum always contains at least the same frequencies than that of the transmitter transmitter 1908.

This two-source electrical configuration by means of four electrodes coupled in pairs makes it possible, on the one hand, for the emitter device, to generate bending movements of the radiating emitter sleeve in the ambient air of the acoustic waves parallel to the plane of the plate and, on the other hand, for the receiving device, to capture these air waves in the same frequency band corresponding to a maximum sensitivity.

The interface system 1900 further comprises a computing device (not shown) similar to that of FIGS. 1 to 17, and connected to the electrodes of the transmitting and receiving devices 1904 and 1916 in the same way, so that the device of FIG. The transmission receives the control signals e t) and e ₂ (t), and the reception device provides the reception signal r (t).

An example of sizing of the piezoelectric discs 1908 and 1918 is illustrated in FIG.

With reference to FIG. 21, the electrodes of the transmission device 1904 comprise four electrodes 2102A, 2102B, 2104A, 2104B respectively covering four quarters of the upper face of the piezoelectric ring 1915. The pairs of two opposite electrodes 2102A, 2102B and 2104A, 2104B are intended to be connected to receive the control signals e ^ t) and e ₂ (t) as in the example of FIGS. 1 to 17. In FIG. 21 the feasibility of vibrating the sleeve 1 914 from a signal The control system was tested by subjecting one of the two pairs of electrodes to a periodic signal of variable frequency and amplitude V Vc.

With reference to FIG. 22 showing the magnitude of variation of the sleeve 914 as a function of the control signal, the resonator disc 1908 has a resonant frequency at 22950 Hz at which the vibration amplitude of the sleeve 914, measured with a vibrometer. laser, is six micrometers peak to peak.

Thus, it is possible to obtain a vibration of the sleeve of a few micrometers, sufficient to generate acoustic air waves along the plate 1902, from a control signal of a few volts.

The interface system 1900 operates as follows.

The computing device provides control signals e ^ t) and e ₂ (t) to the transmitting device 1 904.

In response, the resonator disc 1908 of the transmitting device 1904 vibrates.

The central portion 1912 amplifies the mechanical vibration so that sleeve 1914 tilts and vibrates, based on the amplitude weightings of control signals e t) and e ₂ (t).

The sleeve 1914 forms an impedance matching zone that effectively transmits the mechanical waves in aerial acoustic waves 1 906 in the raz of the plate 1 802, according to a directivity diagram that is a function of the weights.

Thus, as a function of the successive weightings, the aerial acoustic waves 1906 successively exhibit spatial distributions of amplitude in the air 1 903 at the surface of the plate 1 902, different from each other.

In a manner similar to that described for the system of FIGS. 1 to 1 7, the computing device detects and locates the presence of a disturbance in the air on the surface of the plate 1902 created by an obstacle such as a finger from the reception signal r (t). The disturbance begins to be detectable from a certain approach distance from the obstacle, adjustable from a few millimeters to a few centimeters of the plate 1902 as a function of the height of the part of the sleeve opening above the plate of 1902 glass. With reference to FIG. 23, a contactless and non-contacting interface system 2300 according to the invention is almost identical to the interface system 1900 of FIG. 19, so that the same references are used for the identical elements.

The transmission device 1904 of the interface system 2300 further comprises a peripheral rib 2302 extending on the inner face of the periphery of the piezoelectric disk, and bonded to the plate 1902 so that a part of the mechanical vibrations are transmitted 2304 as seismic acoustic waveforms in the plate 1902, in the same manner as occurred in the system of FIGS. 1 to 17, while another portion of the mechanical vibrations are transmitted in the air near the 1902 plate. as aerial acoustic waves 1906.

The receiving device 1916 is modified in the same way as the transmission device 1904.

Preferably, the transmission device 1904 is designed so that the proportion of waves emitted in the two media is comparable. The solid-solid coupling between the emission device and the plate 1902 being more effective than the solid-air transmission, the contact by the rib 2302 is sufficient. Of course, any other type of contact could also be suitable.

The disturbance thus starts before there is contact because of the disturbance of the air waves.

The learning process is therefore modified to include two learnings: the one corresponding to a non-contact disturbance, that is to say only aerial waves, the other corresponding to a disturbance with contact, that is to say a simultaneous disruption of overhead acoustic waves and seismic acoustic waves. The excitation spectrum for the seismic part can be broadband and distributed for example over forty frequencies between 20 kHz and 100 kHz as in the previous case, while the excitation and reception of the air waves will be at a single (for example 22 950 Hz) or two frequencies (for example 22 950 Hz and 65850 Hz) of resonance implementing a bending of the sleeve.

This configuration makes it possible to bond the emitter and receiver transducers to the wall of the plate. The direct coupling between the two transducers via the plate and via the air is therefore stable and independent of any other support device. The transducers remain mechanically coupled to the outside world via coaxial cables of small diameter, typically less than one millimeter representing a weak and constant disturbance. In addition, in the case of mounting of Figure 23 the holes for the passage of the sleeve are sealed so that the plate can be one of the walls of a cage closed and / or sealed. The ambient air can optionally be replaced by any other gas or even other fluid, in particular a liquid and the cage constitute a container so that a localized interaction can correspond either to a finger contact on the outer face of the container or the presence of a disturbance in the liquid consisting of a mechanical impedance break (passage of a small fish near the wall, appearance of an air bubble, etc.).

In another variant, the resonator disk is disposed on the side of the plate where the disturbance is to be detected and the sleeve extends opposite the contact between the disk and the plate. In this way, the sleeve does not pass through the plate and it is not necessary to pierce it.

In another variant, the sleeve extends on either side of the central zone tapering and allowing an impedance matching. The sleeve is then open on one side and closed on the other, or it is open on both sides. In this variant, it is possible to detect disturbances, with and without contact, on each face of the plate.

In development, in order to facilitate the detection of the air waves in the vicinity of the surface of the plate, an arc of tube forming an "antenna ear" can be fixed to the surface of the plate, for example in a corner of the latter. The tube arc is preferably concentric with the receiver sleeve and of the same height as the latter. The thickness of the tube arc may for example be from a few tenths of millimeters to a few millimeters.

The tube arc has the effect of increasing the collecting surface receiving the waves diffracted by the presence of the finger or an object in the monitoring zone and reflect them towards the sleeve. The tube arc for example covers an angular sector equal to 90 ° in the direction of the space where the aerial interactions occur.

The tube arc is for example machined in the same material as that used for the machining of the resonator disk. In this case, the tube arc preferably extends in a circular manner, with an inner radius of the tube arc equal to that of the resonator disc.

Alternatively, the tube arc is made in a separate part, for example molded in a plastic which is then fixed on the plate on the side where the sleeve (or both sides of the plate if there are two sleeves), at a greater distance from the resonator disk. In this case, the tube arc has a parabolic profile, its focus coinciding with the central axis of the sleeve. This profile is adapted to detecting disturbances remote from the receiving device.

The tube arc also allows the receiving device to pick up the received acoustic airwaves in the audible range and thus function as a microphone. The receiver device therefore operates as a dual-media sensor for locating a disturbance with and without contact and for detecting sounds in a certain frequency band, for example in the audible frequency band allowing interaction by the voice.

In addition, still in perfecting, a tube arc can also be arranged around the emission device, in order to increase the intensity of the acoustic field emitted by the emission device along the face of the plate to be monitored.

In the case of emission of acoustic waves in a fluid, especially in water or air, the waves are compression waves and acoustic energy, even limited to the ultrasound band, can alter at high power and in case of prolonged exposure the auditory perception. The excitation must then be done by providing hearing protection for people and living beings by amplifying the received signal typically by a gain of 40 to 80 dB and limiting the excitation amplitude to a level compatible with the thresholds of security. To fix ideas, a vibration amplitude 1 μηι in the air at 23 kHz generates a dynamic pressure of 64 Pa, or about 130 dB acoustic equivalent (if our hearing threshold of 2.10 ^"5 Pa, remained valid at 23 kHz), the ultrasonic mechanical energy, even if not perceived by the ear receivers, must be limited, this being possible possibly by carrying out, in addition to the amplification of the signal received together with the limitation of the excitation signal, intermittent excitation, generating in the medium a lower average exposure value, typically less than 85 dB at 1 cm from the source, for a pressure reference of 2.10 ^"5 Pa. Thus, the acoustic energy emitted in the fluid can, punctually in time, be greater than 85 dB, especially very close to the source, but remains on average over time and everywhere in the fluid medium, less than 85 dB either for the ultrasound domain but of course also po on the audible domain.

In addition, in the case of an amplification, the detection of weak disturbances is facilitated if the gain is chosen so that the maximum amplitude peak-to-peak of the received vacuum (ie non-contact) signal reaches the full scale of the ADC ("Analog to Digital Converter") analogue digital converter used and if the signal-to-noise ratio is improved by performing, following the amplification, bandpass filtering corresponding to the excitation spectrum used (example 20kHz-100kHz).

In another embodiment of the invention, a system similar to those described above could be used in the field of non-destructive testing. Indeed, any other cause of impedance breaking at the surface or inside of an object will cause a disturbance that the use of seismic acoustic waves emitted with spatial distributions of amplitude in the object at frequencies respective, different from each other, can detect as explained above. These causes can be small defects of wear or fatigue in the materials, in particular cracks or splinters in elongated materials with constant section such as rails, tubes, rods, whose section must remain intact on lengths greater than the coverage area of the transducers, but also localized delamination occurring on surface materials such as blades, shells, plates.

Since the location method described above is extremely sensitive to very small disturbances, it will be advantageous to use it for the detection of very small or very small delamination zones, or even to detect the presence of drops on the surface of a screen. breaks, quantities of bubbles or density fluctuations in a liquid contained in a tank, or even follow or characterize the maturation of a food product. For all these cases, an acoustic pulse in the form of a burst with frequency modulation with spatial distribution of amplitude varying over time, such as the emission devices which have just been described and whose radiation pattern varies over time. course of time, is issued in the middle where a disturbance is likely to occur. These acoustic waves are emitted first during a training phase with typical disturbances to obtain reference reception signals, and then during a monitoring phase where the reception signal is compared to the reference reception signals.

Moreover, the methods for detecting and locating a disturbance, in particular a contact, described above could be modified to detect multiple disturbances. Indeed, by virtue of the fact that the reception signal is normalized relative to the reference reception signals corresponding to single disturbances, it is possible to detect multiple disturbances by increasing the training set of the linear combinations of single disturbances.

This property has been verified by experience on a touch surface system such as that of FIGS. 1 to 17, but with as support a polyamide nylon PA12 plastic shell rather than a glass plate. The reason is as follows: in the case where the radiation pattern is of slow spatial variation, that is to say, in the Fourier space, associated with lower spatial frequencies than those of the finger or the disturbance, which is the case of a dipolar radiation, the disturbance is proportional to the contact surface. This is all the more true as the perturbation of the volume waves is globally weak and the viscous damping perturbation, a non-linear phenomenon dependent on the speed of vibration, is lower. All that remains is the perturbation linked to the wave diffraction phenomenon, the received field diffracted by the multiple interaction (s) being, according to the Huygens-Fresnel principle, the Kirchhoff-Sommerfeld integral applied to the surface or surfaces of the 'interaction. Huygens-Fresnel's principle is that each zone of interaction behaves like a distribution of secondary source points. The total diffracted field for a multiple contact is therefore the sum of the diffracted fields for point contacts. This reasoning is even more valid in the air where there is practically no viscous damping, but only diffraction of the air waves.

With reference to FIG. 24, the first curve shows the frequency amplitude of the relative normalized reception signal of a contact at a position A of the shell. The second curve shows the frequency amplitude of the relative normalized reception signal of a contact at a position B of the shell. And the bottom curve shows the superposition, on the one hand, of the sum of the first two curves, and, on the other hand, of the curve obtained by direct learning by simultaneously exerting two contacts at the A and B positions. positioning of the contacts close, we note that the two curves are almost identical and therefore the sum disturbance is the sum of the individual disturbances.

It is clear that systems such as those described above make it possible to detect and locate a disturbance without requiring acoustic waveguides, or to perform transit time calculations. With reference to Figures 25 and 26, other control signals than those presented above could be used.

For example, an interesting case would be to take the out-of-plane component of the total acoustic field indicated previously: to fix k = 0.5 and to introduce a phase shift φ between the two dipolar sources:

The amplitudes of the control signals ei (t) and e ₂ (t) are then constant in time and their frequencies are the same. The parameter that changes is the phase shift φ between the control signals, and therefore between the two dipolar sources.

FIGS. 25 and 26 illustrate the directivity diagrams observed experimentally on a plate of dimensions 360 mm × 220 mm × 3.3 mm for <p = 0 and φ = π Ι 2. The other parameters are f = 40400 Hz, k = 0.5, Volts, so that It is thus possible to radically change the directivity diagram by simply changing the phase shift between the control signals ei (t) and e ₂ (t) for example by 40 steps spaced by 2 ° between 0 and 90 °.

Referring to Fig. 27, a contactless and non-contacting interface system 2700, further adapted to produce a vibrotactile feedback in the glass plate, will be described.

The system 2700 has the same elements as the system of Fig. 19, with further a vibrating movable member 2702 inserted into the sleeve of the resonator disc 1910. The movable member has a rod 2704 inserted into the sleeve and extending along the axis of the latter. The movable piece further comprises a feeder 2706 attached to the rod eccentrically relative to the axis of the rod. The flyweight is for example in the form of a half disc and is preferably located on the other side of the resonator disc as the sleeve.

The moving part is trapped in the sleeve, but can continue to rotate around the axis of the rod. A vibrotactile feedback can thus be generated, for example to validate an action or a choice of a user acting on the interface system, by providing control signals e ^ t) and e ₂ (t) sinusoidal and in quadrature one of the other, at the resonance frequency of the resonator disk, for example at 22 950 Hz. Thanks to such control signals, the flyweight is rotated with a speed which depends directly on the amplitude of the vibration. ultrasound of the sleeve.

For example, it has been found that, for an inner diameter of the 3 mm sleeve, the moving part can rotate at a speed that can easily reach 100 to 200 revolutions per second, thus producing a strong vibration transmitted in the hull or plate. To avoid rotation of the flyweight, it is sufficient to provide control signals in phase with each other and with a lower intensity.

As a variant, the mobile vibrating part can advantageously be housed in the sleeve of the receiver device, but switched to transmitter mode at the moment when it is desired to apply the vibrotactile feedback, by supplying control signals in the same way as for the transmitting device.

The advantage of producing the vibrotactile feedback from the receiver device lies in the fact that the acoustic waves emitted by the emission device are thus not disturbed by the friction of the moving part against the inner wall of the sleeve. The emission radiation pattern is thus stable.

On the contrary, since the receiving device receives the air waves and the acoustic waves conveyed by the plate, the contact of the moving part against the inner walls of the sleeve (of the receiving device) does not disturb either very little or not. constant way that can easily be corrected by signal processing, the reception signal.

Note also that the invention is not limited to the embodiments described above. It will be apparent to those skilled in the art that various modifications can be made to the embodiments described above, in the light of the teaching just disclosed.

In particular, the different spatial distributions from one wave to another could be phase spatial distributions, instead of or in addition to spatial amplitude distributions. In particular, the different types of control signals described above (change in the contribution of the two sources and change in the phase shift between the two sources) result in different phase spatial distributions from one wave to another. In addition, the control signals might not be monochromatic, but instead have an extended spectrum. Thus, acoustic waves emitted (in a solid or in the air, according to the embodiment) would also have an extended spectrum. In this case, the transmission device would be designed so that the spectra of the acoustic waves have, each at at least a certain frequency, respective spatial distributions of amplitude or of phase different from each other. For example, spatial distributions change for all frequencies, from one acoustic wave to another.

In the following claims, the terms used are not to be construed as limiting the claims to the embodiments set forth in this specification, but should be interpreted to include all the equivalents that the claims are intended to cover because of their formulation and whose prediction is within the reach of those skilled in the art by applying his general knowledge to the implementation of the teaching that has just been disclosed to him.

Claims

1. A system (100; 1800; 1900; 2300) for detecting and locating a disturbance of a medium (102; 1802; 1903; 1902; 1903), comprising:

transmission means (424, 304, 306, 424, 1806, 1904) of successive acoustic waves in the medium (102, 1802, 1903, 1902, 1903),

means for receiving (108; 1828; 1916) successive acoustic waves after their propagation in the medium (102; 1802; 1903; 1902; 1903), adapted to provide a reception signal from successive received acoustic waves, and means (424) for detecting and locating the disturbance in the medium from the reception signal,

characterized in that the transmitting means (424, 304, 306, 424, 1806, 1904) is adapted so that the amplitude and / or phase spectrum of each acoustic wave having at least a certain frequency, an amplitude, respectively a phase, varying in the medium according to a certain spatial distribution of amplitude, respectively of phase, these spatial distributions of amplitude, respectively of phase, successive acoustic waves are different from each other.

The system (100; 1800; 1900; 2300) according to claim 1, wherein the transmitting means (424,304; 424,1806; 1904) comprises:

an emitting device (304; 1806; 1904) comprising first and second acoustic wave sources (402,403,404,405,406A, 406B, and 402,403,404,405,408A, 408B; 1826, 1824, and 1820, 1826, 1822) respectively having first and second radiation patterns, concentric and different from each other,

means (424) for varying the relative weighting of the acoustic wave amplitudes of the first and second sources (402, 403, 404, 405, 406A, 406B, and 402, 403, 404, 405, 408A, 408B, 1818, 1826 , 1824, and 1820, 1826, 1822), the successive weights corresponding respectively to the successive spatial distributions.

3. System (100; 1800; 1900; 2300) according to claim 2, wherein each radiation pattern has an axis (A1, A2) in the direction of which it is zero, the axes forming a non-zero angle between them.

4. System (100; 1800; 1900; 2300) according to claim 2 or 3, wherein:

each acoustic wave source (402, 403, 404, 405, 406A, 406B, and 402, 403, 404, 405, 408A, 408B, 1818, 1826, 1824, and 1820, 1826, 1822) has two transducer elements piezoelectric,

the transmitting means (424, 304; 424, 1806) comprise means (424) for biasing the two piezoelectric transduction elements to two potentials opposite one another.

The system (100; 1900; 2300) of claim 4, wherein the transmitting device (304) includes a piezoelectric element (405) coupled to the medium (102) and four electrodes (406A, 406B, 408A, 408B). covering a respective quarter of a face of the piezoelectric element (405), the two transducing elements of the first source (402, 403, 404, 405, 406A, 406B) respectively comprising two opposite electrodes (406A, 406B) to each other and the two transducing elements of the second source (402, 403, 404, 405, 408A, 408B) respectively having the other two electrodes (408A, 408B) opposite to each other.

The system (100; 1800; 2300) according to any one of claims 1 to 5, wherein:

the medium (102; 1802; 1902) has a plate having a contact surface (104A, 104B),

acoustic waves are seismic acoustic waves propagating in the plate,

the disturbance is a contact on the contact surface.

The system (1900; 2300) according to any one of claims 1 to 5, wherein:

the medium comprises a fluid (1903) on the surface of a plate (1902), the acoustic waves are acoustic waves of compression propagating in the fluid (1903) on the surface of the plate (1902), the disturbance is the presence of an impedance break on the surface of the plate, for example caused by the presence of an obstacle.

8. System (1900; 2300) according to claims 5 and 7, wherein the piezoelectric element (1908) comprises a sleeve (1914) designed to emit acoustic compression waves.

9. A method for detecting and locating a disturbance of a medium, comprising:

providing (1714) control signals to an acoustic wave emitting device, so that said transmitting device emits successive acoustic waves in the medium,

receiving (1716) a reception signal from an acoustic wave receiving device receiving the successive acoustic waves after their propagation in the medium,

detecting and locating (1718 - 1748) the disturbance in the medium from the reception signal,

characterized in that

the control signals are designed so that the amplitude and / or phase spectrum of each acoustic wave having, at at least a certain frequency, an amplitude, respectively a phase, varying in the medium according to a certain spatial distribution of amplitude, respectively of phase, these spatial distributions of amplitude, respectively phase, successive acoustic waves are different from each other.

10. A method for detecting and locating a disturbance of a medium according to claim 9, wherein:

the control signals are supplied intermittently so that the average exposure power, even in the ultrasound range, remains below 85 dB, with a reference of 2.10 ^-5 Pa, in the air at one centimeter from the device. emission of acoustic waves,

the control signals have a certain frequency band of excitation,

and further comprising, before detecting and locating the disturbance in the medium from the reception signal: amplifying the reception signal and converting it by means of an analog-to-digital converter, the amplification being configured so that the amplitude of the signal received in the absence of disturbance reaches the full quantization scale of the analog-to-digital converter; digital,

performing bandpass filtering of the reception signal over a frequency band corresponding to the excitation frequency band.

1 1. Computer program downloadable from a communication network and / or recorded on a computer readable medium and / or executable by a processor, characterized in that it comprises instructions for performing the steps of a detection method and of locating a disturbance of a medium according to claim 9 or 10, when said program is run on a computer.