EP2457146A1

EP2457146A1 - Method and device for the locating at least one touch on a touch-sensitive surface of an object

Info

Publication number: EP2457146A1
Application number: EP10745674A
Authority: EP
Inventors: Jean-Pierre Nikolovski; Yuan Liu; Moustapha Hafez; Nazih Mechbal; Michel Verge
Original assignee: Centre National de la Recherche Scientifique CNRS; Commissariat a lEnergie Atomique CEA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Centre National de la Recherche Scientifique CNRS; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2009-07-21
Filing date: 2010-06-30
Publication date: 2012-05-30
Also published as: JP2012533810A; US20120120014A1; JP5768814B2; WO2011010037A1; FR2948471B1; US8913039B2; FR2948471A1

Abstract

The invention relates to a method for locating at least one touch on a touch-sensitive surface of an object, comprising the following steps: monitoring for (100) at least one touch by propagating (102), on the touch-sensitive surface of the object, elastic mechanical waves from at least one emission point of the object, and by detecting (104) said elastic mechanical waves in at least one reception point of the object, in order to obtain at least one sensed signal; and locating (200) at least one touch on the touch-sensitive surface of the object by comparing certain spectral characteristics of the sensed signal to a set of reference characteristics. The monitoring step (100) comprises measuring (104, 106) the sensed signal during a starting time interval (t3) during a transition phase of the propagation of the emitted waves, for supplying, to said at least one reception point, information on radiation interfered with by said at least one touch.

Description

METHOD AND DEVICE FOR LOCATING AT LEAST ONE TOUCH ON A TOUCH SURFACE OF AN OBJECT

The present invention relates to a method for locating at least one touch on a touch surface of an object. It also relates to a device for implementing this method.

Many touch-surface objects are known, including mobile phones or other portable digital personal assistance devices. Their touch interface is usually a flat, rectangular screen with which a user can interact with a stylus or one or more of his fingers. It will be noted, however, that the invention applies more generally to any type of object having a touch surface that is not necessarily flat or rectangular contour.

Each of these objects implements a method of locating at least one touch using one or more detection techniques.

The international patent application published under the number WO 2006/133018 discloses a method of locating a touch on a tactile surface implementing several independent detection techniques each providing a location estimate and including a step of cross-checking the estimates provided according to the different techniques to obtain a final result with improved accuracy. Among the techniques envisaged, one of them uses the repeated emission in the tactile surface of elastic mechanical waves, for example surface acoustic waves, and the detection of these elastic mechanical waves, to locate a touch by analysis of the disturbance of this touch on the waves detected. The implementation of this technique envisaged in this document does not provide a very accurate estimate, it is advantageously associated with other techniques to refine the estimate. But the multiplication of localization techniques used increases the processing of the signals received.

A location method using only one technique for detecting and analyzing the detected signals is preferable. In particular, the invention relates more precisely to a method implementing only a localization technique by analyzing the perturbation of a single or multiple touch on the propagation of elastic mechanical waves in a tactile surface which alone can provide a accurate estimate. The invention thus applies to a method of locating at least one touch on a tactile surface of an object, comprising the following steps:

monitoring of at least one touch by propagation, in the tactile surface of the object, of elastic mechanical waves from at least one emission point of the object, and by detection of said elastic mechanical waves at least one receiving point of the object to obtain at least one signal picked up, and

- Locating at least one touch on the touch surface of the object by comparing certain characteristics of the signal picked up to a set of reference characteristics.

Such a process is described in the international patent application published under the number WO 2008/142345. It results in a precise location by propagating waves having a plurality of frequency components corresponding to vibratory eigenfrequencies of the object. The propagation of these waves for a certain time in the tactile surface makes it possible to materialize vibration patterns at different wavelengths, in particular resonance figures of bending modes. These have the characteristic of being more strongly disturbed than the resonant patterns of vibration modes in the plane of the tactile surface of the object so that the damping generated by a finger brought into contact with the surface, even in the case where it is thick, measurably varies from one mode to the other and from one contact position to another. It is thus possible to locate a touch by a learning method, as soon as a sufficient number of resonance figures is materialized on the surface of the object.

But many problems are not solved by this process, including the recognition, location and interpretation of a multiple touch. Indeed, the document WO 2008/142345 teaches that the damping is not necessarily a linear function of the covering surface (except to choose a subspace of resonance modes) and in the case where it would be a linear function of the covering area, does not indicate if it is still possible to locate a touch. On the other hand, for a damping to be a linear function of the surface in contact, it would be necessary for the energy to be uniformly distributed on the surface of the object. But in this case, there would be more resonance and no more knots or bellies of vibration. Nothing would then make it possible to discriminate the position of a touch.

Other methods are known for recognizing and / or interpreting multiple touches. The international patent application published under the number WO

2005/1 14369 describes for example a transparent touch screen on which the multiple touches are detected according to a principle of capacitive technology. However, this technology has the following drawbacks: it requires a transparent electrode layer and a matrix of capacitive sensor nodes.

International patent application published under the number WO 2008/085785 describes another example of a method for identifying and discriminating the nature of a multiple contact (thumb, palm) by an analysis consisting of a segmentation of the tactile image obtained. and identification of the discretized pattern with predefined patterns. This method has the particular disadvantage of requiring a discretized touch interface.

International Patent Application Publication No. WO 2008/085759 discloses another example of a method for merging the data of a multi-touch interface. But this process requires at least one secondary device and the data synchronization of several devices.

Finally, the international patent application published under the number WO 2008/085784 describes a touch screen device using a dictionary of gestures associating multiple touches to functions. But the implemented method requires comparing all the predefined elements for the recognition of a movement and only takes into account summary parameters of the multiple touches.

Another problem of the method described in WO 2008/142345 resides in the high selectivity of the resonant figures and in the fact that it is then necessary to have a good frequency resolution for measuring an amplitude at the resonance peaks or at the resonance peaks. less able to interpolate to extrapolate the value of a resonance peak with or without contact. But this process works with good accuracy only with resonance figures. By working outside the vibratory eigenfrequencies of the object, it is also possible to obtain a stationary state of propagation in the tactile surface, but the figures obtained are much less discriminating.

Yet another problem of this method lies in the time of establishment of a stationary state of propagation in the tactile surface, necessary to obtain the resonance figures. This time lengthens the processing time to locate a touch. It may thus be desired to provide a method of locating at least one touch on a tactile surface of an object that makes it possible to overcome at least some of the aforementioned problems and constraints.

The subject of the invention is therefore a method for locating at least one touch on a tactile surface of an object, comprising the following steps:

locating at least one touch on the touch surface of the object by comparing certain spectral characteristics of the signal picked up with a set of reference characteristics,

wherein the monitoring step comprises a measurement of the signal picked up during a time interval beginning during a transient phase of the transmitted wave propagation, for the provision of radiation information, disturbed by the at least one touch , auditing at least one receiving point.

It will be noted that the transient phase can begin from the moment of excitation marking the beginning of the emission of elastic mechanical waves until the moment of the first reflections on the edges of the tactile surface of the object.

The invention proceeds from a very different approach from conventional approaches using elastic mechanical wave propagation. Surprisingly, it appears that by considering, not the establishment of stationary resonance figures, but the propagation of the elastic mechanical waves in the tactile surface during the transitory preliminary phase of propagation, in particular by considering the diffraction phenomena in pulse mode, it also captures signals that can be discriminating according to the location of a single or multiple touch. Moreover, it has been observed that in proceeding in this way, we were not dependent on the eigenfrequencies of the object, so that we can overcome the problem of selectivity of the resonance peaks and that of of their stability. This also allows a much wider choice of frequencies.

Thus, instead of obtaining and observing stationary figures, especially resonance figures, transient radiation patterns are obtained, usually referred to as "diffraction impulse patterns", characteristic of a disturbance propagated by a simple touch or multiple. We note, moreover, that these transient figures are much faster to obtain than stationary figures, so that the processing of the data captured to obtain the location of the single or multiple touch is accelerated. These transient figures are also dependent on excitation frequencies, whether they are eigenfrequencies of the object or not.

Moreover, it will also be noted that what is measured is not necessarily an attenuation of a vibration due to the presence of a touch on the tactile surface, but a signal that increases or decreases depending on the presence of the touch single or multiple favors or decreases the exposure of the area where the receptor (s) is located.

Optionally, the measurement of the sensed signal extends beyond the restoration of a stationary phase of the propagation of the transmitted waves, for the provision of an illumination information to said at least one reception point.

Also optionally, said reference characteristics correspond respectively to single and multiple touches at predetermined areas of the touch surface.

Optionally also, the transmitted waves comprise a plurality of predetermined frequency components all distinct from the vibratory eigenfrequencies of the object.

Also optionally, each frequency component of the transmitted waves is chosen so as to be at a frequency distance of more than twice the width of a resonance energy peak corresponding to any vibratory natural frequency of the object.

Also optionally, the characteristics of the sensed signal compared to the reference characteristics are spectral amplitudes of the signal captured at said predetermined frequency components forming a so-called "measured" vector and the set of reference characteristics comprises a set of reference vectors associated with each at a single or multiple touch, this reference set being constructed during a prior learning step, similar to the monitoring step, in which different single and multiple reference touches are measured.

Optionally also, the reference vectors being ordered in the reference set according to the value of their standard, the location step comprises the following sub-steps:

- calculation of the norm of the vector measured, selecting a subset of the reference set representing a range of norms in a predetermined neighborhood of the norm of the measured vector, and

searching for the reference vector closest to the vector measured in this subset according to a predetermined distance function.

The invention also relates to a device for locating at least one touch on a tactile surface of an object, comprising at least one transducer designed to emit and pick up elastic mechanical waves propagating in the tactile surface of the object. , and an electronic central unit, connected to said at least one transducer, programmed to:

propagating elastic elastic waves in the tactile surface of the object from said at least one transducer and detecting said elastic mechanical waves by said at least one transducer to obtain at least one signal picked up, and

locate at least one touch on the touch surface of the object by comparing certain spectral characteristics of the signal picked up with a set of reference characteristics,

in which the electronic central unit is further programmed to measure the signal picked up during a time interval beginning during a transient phase of the propagation of the transmitted waves, for the supply of radiation information, disturbed by said least one touch, auditing at least one receiving point.

Optionally, a device for locating at least one touch on a touch surface according to the invention further comprises the object, its touch surface and means for holding the touch surface on the object arranged in the vicinity of zones. convex discontinuity of the periphery of the tactile surface.

Optionally also, the electronic central unit is further designed to:

defining at least one simple or multiple trace from a plurality of touches located successively on the tactile surface,

interpreting this simple or multiple plot as a predetermined function to be performed by comparing certain features of that plot with a set of reference features. 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 schematically represents in perspective a device for locating at least one touch on a touch surface of an object, according to a first embodiment of the invention,

FIG. 2 diagrammatically shows in perspective a device for locating at least one touch on a touch surface of an object, according to a second embodiment of the invention;

FIG. 3 diagrammatically represents the functional structure of the device of FIG. 1 or 2,

FIG. 4 represents a front view of a touch screen of the device of FIG. 1 or 2, according to a first variant,

FIG. 5 represents a front view of a touch screen of the device of FIG. 1 or 2, according to a second variant,

FIG. 6 illustrates the successive steps of a method of locating at least one touch on a tactile surface of an object, according to one embodiment of the invention,

FIG. 7 illustrates the successive steps of a method of interpreting at least one touch on a tactile surface of an object, according to another aspect of the invention,

FIG. 8 schematically represents different symbolic interpretations of different successive locations of single touches, and

- Figure 9 schematically shows different symbolic interpretations of different successive locations of multiple touches. The device 10 for locating at least one touch on a tactile surface of an object, represented in FIG. 1, comprises:

a microcomputer 12 including in particular a screen 14 and a keyboard 16,

an object 18 of the interactive tablet type, connected to the microcomputer 12 via a link 20, wired or radio.

The interactive tablet 18 comprises a frame 22 and a touch surface 24 held by the frame on at least a portion of its edges. The touch surface 24 is for example in the form of a metal plate, glass or plastic, vibrating when elastic mechanical waves propagate in its thickness. It can be rectangular in shape, especially in 4/3 format. Specifically, it may have a length of 100 mm, a width of 75 mm and a relatively small thickness relative to its length and width, in particular between 100 microns and 4 mm, for example 450 microns. This thickness is also very small compared to the characteristic dimension of an area of the touch surface 24 that can be touched, a user's finger generally representing a touch of diameter close to one centimeter.

In the example illustrated in FIG. 1, three piezoelectric transducers E, R1 and R2 are fixed on the inside face of the touch plate 24, that is to say that which is not accessible to the touch and facing inwards. of the frame 22. They can in particular be glued to the plate 24, by means of a conductive epoxy glue or cyanoacrylate.

These piezoelectric transducers are, for example, ferroelectric ceramic PZT type transducers. They include:

an emission transducer E capable of transmitting elastic mechanical waves (ie acoustic waves in the broad sense) in bending modes, such as, for example, antisymmetric Lamb waves, such that they propagate in the touch plate 24 ,

two reception transducers R1 and R2 capable of sensing elastic mechanical waves propagating in bending modes in the touch plate 24.

These three transducers are preferably arranged outside any axis of symmetry of the touch plate 24. Moreover, they can be of small size and of any geometrical shape. In particular, for a touch plate 24 with the aforementioned dimensions (75 mm × 100 mm × 0.45 mm), they may have an area of between a few square millimeters and a square centimeter. If the emission transducer E is excited by a 10 V signal, the reception signals provided by the reception transducers R1 and R2 can reach 0.2 V without amplification.

The transducers E, R1 and R2 are connected to an electronic control unit, for example integrated in the microcomputer 12 and programmed to:

propagating elastic elastic waves in the tactile plate 24 from the piezoelectric transducer E and causing these waves to be detected resilient mechanics by the piezoelectric transducers R1 and R2 to obtain two picked signals, and

- Locate at least one touch on the touch plate 24 by comparing certain characteristics of the signals captured to a set of reference characteristics.

According to a first aspect of the invention, the electronic central unit of the microcomputer 12 is more precisely programmed to measure the signals picked up during a time interval beginning during a transient phase of the propagation of waves emitted from of the piezoelectric transducer E, for the provision of radiation information at the reception points materialized by the piezoelectric transducers R1 and R2, according to a method which will be detailed with reference to FIG.

The elastic mechanical waves emitted in the touch plate 24 from the piezoelectric transducer E are indeed locally absorbed, blocked or partially reflected when at least one finger or a stylet is in contact with the plate. This causes a disturbance of the radiation information provided to the reception points R1 and R2 in transient phase of propagation. By extracting, for example, certain amplitude and phase parameters at predetermined frequencies from this disturbed radiation information, referred to as the "disturbed diffraction impulse response", it is possible to compare them with reference parameters extracted from a parameter library. linked to predetermined touches or extracts from a modeling function of the diffraction impulse response disturbed by a single or multiple touch (for example via a Kirchhoff-Sommerfeld type formulation in pulsed mode) and to deduce a possible location therefrom. a single or multiple touch.

Thus, for each single or multiple touch on the touch plate 24, using one or more fingers or a stylus, a location of this single or multiple touch that can for example be displayed on the screen Of the microcomputer 12. By extension, for a succession of single or multiple touches detected on the touch plate 24, forming a single or multiple trace 26, a location of this path 26 can be viewed on the screen of the microcomputer 12, under the shape of a kinematic curve 28 obtained by interpolation of the detected trace 26.

According to another embodiment of the invention illustrated in FIG. 2, the touch plate 24 can be transparent and integrated into an electronic device embedded 30, such as a mobile phone or any other portable digital personal assistance device. In this case, it can also fulfill the function of a display screen of the kinematic curve 28 obtained by interpolation of the detected trace 26.

As represented in FIG. 3, the device 10 or 30 may comprise a microcontroller 32 provided with an arithmetic and logic unit, possibly driven by the microcomputer 12 in the case of the device 10. This microcontroller 32 has an output connected to a digital-to-analog converter 34 whose output is connected, if necessary via an amplifier 36, to the emission transducer E.

Moreover, the two reception transducers R1 and R2 can be connected to two analog / digital converters 38 and 40, themselves connected to or integral parts of the microcontroller 32. The analog / digital converters 38, 40 and the microcontroller 32 are capable to perform a sampling of the signals picked up on at least 8 bits, preferably on 10 bits, or even on 12 bits or more at a rate of at least 200 kHz.

According to an alternative embodiment, or more particularly in the case of a test bench, the analog / digital and digital / analog converters can be replaced by an acquisition card and an arbitrary function generator.

The connections to the transducers E, R1 and R2 may consist in particular of coaxial cables of the audio type or of any other shielded connection.

FIG. 4 represents a front view of the touch plate 24 of the device of FIG. 1 or 2, according to a first variant embodiment. Rectangular, the plate 24 is fixed to the frame 22 in four substantially punctual areas P located at the four corners of the rectangle. These zones are the only ones to impose mechanical stresses on the plate. They are thus preferably located in the areas of the plate 24 least affected by the propagation of elastic mechanical waves, including the angular areas at the edges of the plate.

According to a second variant embodiment illustrated in FIG. 5, the plate 24 is of more complex shape than rectangular. A first advantage of this more complex form is that the radiation information in the transient phase of propagation, or diffraction pulse mode with taking into account the first reflections on the edges, are likely to be more complex, therefore more discriminating according to the different locations of single or multiple touch. Indeed, in a general way, in a solid object, and in particular in guided propagation, the vibratory energy comprises longitudinal and transverse components whose proportions change as a function of frequency. However, the conditions of reflection and of conversion of acoustic modes to the limits of the solid object depend on the nature of the vibration so that the conditions of acoustic illumination of the solid object in transient state and of vibrational energy accumulation. during successive reflections in certain areas of the object will depend on the excitation frequency, and this especially as the contours and cutting (including training of songs) of the object are complex. In addition, this more complex shape has more angular areas P where the elastic mechanical wave radiation is less important and where the plate 24 can be fixed to the frame 22 without the risk of disturbing its ability to locate a single or multiple touch .

Thus, according to the present invention, it may be advantageous to cut or mold the touch surface of the object in a variable contour or complex shapes, for example sawtooth, and preferably shaped convex polygon for a plate, or oscillating with a variable oscillation pitch, or in three dimensions.

It will also be noted that, in the context of the invention, it is possible to provide more or fewer piezoelectric transducers for transmission and / or reception, the minimum being conceivable being a single transducer that is successively transmitter and receiver. In the nonlimiting example of FIG. 5, it has been chosen to provide two emitting transducers E1, E2 and two receiving transducers R1, R2.

The choice of the number of transducers and their mode of operation according to the envisaged applications is notably guided by the following observations:

the complexity of the radiation of the transmitted waves is increased by increasing the number of transmitting and / or receiving transducers, especially when these are distributed in diametrically opposite zones,

- When several transducers emit alternately the same frequencies, different radiations can be recorded. The device 10 or 30 which has just been described operates in a manner which will now be detailed with reference to FIG.

At regular intervals, for example at a rate of several tens of measurements per second, in particular fifty to one hundred measurements per second, the micro- computer 12 or the microcontroller 32 initiates a step 100 of monitoring the outer face of the touch plate 24 followed by a step 200 of locating a single or multiple touch.

For each monitoring step 100, at a time t ₀ , elastic mechanical waves are emitted (102) in the plate 24. They propagate therein according to two distinct propagation phases: a first phase of transient propagation, extending from the instant t ₀ at a time t i, during which the emitted wavefront reaches the receiver (s), either directly or indirectly after one or more reflections, without the addition of the received waves being still stable over time; a second stationary propagation phase, extending from the instant ti to a monitoring end time X ₂ , during which the addition of the new waves received is compensated by the natural damping of the structure so that the amplitude peak-to-peak signal is stable over time. During the transient phase, it is thus possible to speak of a diffraction impulse response or, in an imaginary manner, of radiation information received at the receiving point (s), according to a notion of "flow". During the stationary phase, we will speak rather of illumination information at the point (s) of reception, according to a notion of stable result of this flow.

Following the emission 102 of elastic mechanical waves in the plate 24, the monitoring step 100 comprises a detection 104 of these elastic mechanical waves in at least one point of reception of the plate 24 to obtain at least one a signal picked up. This detection 104 is started at a time t ₃ and continues until a time t ₄ end of detection 106 by measuring the signal picked up during this time interval. It will be noted that, according to the invention, the measurement starts during the transient phase of the propagation of the transmitted waves, for the provision of radiation information at the point (s) of reception. In other words, the time t ₃ for launching the measurement is between the instants t ₀ and \ _λ . The time t ₄ end of the measurement can also be between the times t ₀ and ti so that the measurement is integrally carried out in transient phase. However, as a variant, the measurement of the signal picked up may extend beyond the establishment of the stationary phase of the propagation of the transmitted waves, for the supply, in addition to the aforementioned radiation information, of an illumination information. at the point (s) of reception. In other words, the end time t ₄ of the end of the measurement can be between the instants t ₁ and t ₂ . The monitoring step 100 is followed by a step 200 of locating a single or multiple touch in the course of which a touch or several simultaneous touches on the touch plate 24 are identified and localized.

These two steps of monitoring 100 and locating 200 will now be detailed.

STAGE OF SURVEILLANCE 100

During each monitoring step 100, the microcomputer 12 or the microcontroller 32 emits by the emission transducer E, or the emission transducers E1, E2 disposed at possibly diametrically opposite points of the object (of in order to vary the radiation patterns) elastic mechanical waves, in particular Lamb waves and more particularly antisymmetric Lamb waves. The emission transducer E, or the emission transducers E1, E2, emit not simultaneously, but alternately so as to contrast the radiation and illumination figures (a simultaneous emission would have the effect of homogenizing the radiation and illumination and to remove spatially discriminating features). In addition to Lamb waves in isotropic plates, the transducer E, or the transducers E1, E2, is (are) capable of emitting waves in bending modes in homogeneous or heterogeneous flat or curved shells.

During this step also, in one embodiment of the invention comprising several emitters, they can emit all together at least once so as to completely and uniformly illuminate the touch plate 24 to obtain a measurement whose standard is indicative of a single or multiple touch and a covering surface.

The transmitted waves are composed of a number Q of predetermined frequencies. They are captured directly, or indirectly after one or more reflections, by the receiving transducers R1, R2 activated in the transient propagation phase. As indicated above, after multiple reflections on the edges of the touch plate 24, there appear standing waves associated with illumination figures which can also be picked up by the receiving transducers R1, R2.

The number Q of these predetermined frequencies is generally greater than 10 and is preferably greater than 100, or even between 200 and 500. These predetermined frequencies are not in the vicinity of a resonance peak of the object. They are even more than twice the width at mid-height (in energy) of a resonance peak, knowing that a resonance peak is located at any natural frequency of the touch plate 24 integrated in the object. They can be chosen from the spectrum of the signals picked up by the reception transducers R1, R2. They are also chosen according to the complexity of the radiation information and / or the illumination figures that they generate. For example, the more complex a pattern of radiation and / or resultant illumination that is complex and not symmetric, the more the corresponding frequency is of interest.

The predetermined frequencies may also be chosen on the basis of a distribution of Q frequencies in a range of frequencies covering a broad spectrum from the point of view of the spatial frequencies, in particular between 1 and 100 kHz.

For example, for a frequency range from 20 kHz to 80 kHz, the Q distributed frequencies Fi can be predetermined by the following formula:

Fi = 20 + ( ^{80 ~ 20} ) *, in kHz, for 1≤i≤Q. To perform the monitoring step 100 at Q predetermined frequencies, the microcomputer 12 or the microcontroller 32 can emit by the transducer E, or the transducers E1, E2 a frame comprising Q waveforms superimposed Q predetermined frequencies. This emission can be carried out during a transmission time window of sufficient duration so that stationary waves are built in the plate 24. This duration may for example be between 2 and 25 ms, and in particular be of the order of 5 ms . This emission can be carried out continuously or repetitively continuously by the generation of an arbitrary signal, resulting from the superposition of the Q frequencies over a time window of 5 ms.

During the monitoring step, the mechanical waves can be picked up by the reception transducers R1 and R2 during a reception time window which can start after the transmission time window so as to allow the establishment of standing waves. or from the beginning of the transmission time window so as to capture the process of acoustic radiation in the object which manifests itself as soon as the direct signal is received and during the first successive reflections on the edges of the plate 24. thus consider obtaining a signal measured in milliseconds, for example 5 or even 2 ms. By way of comparison, according to the prior art disclosed in the document WO 2008/142345, such an acquisition window would have allowed frequency resolution by fast Fourier transform only at 500 Hz. Such a resolution would have been quite insufficient given the width of a resonance peak, close to 200 to 300 Hz.

As a variant, in the case where the transmission is intermittent, the reception time window may begin after the first transmission frame. In addition, the reception time window can follow the transmission time window without covering it: in this case, it may be possible to use only one piezoelectric transducer for both transmission and reception. In this case also, the receiving transducers are not interested in the stationary phase, in addition to the transient phase, but only detect a pure impulse phase which includes the acoustic extinction phase of the object.

From the signals picked up by the reception transducers R1, R2 and sampled over an acquisition time window of duration T = t ₄ - t ₃ = N ^* Te, where N denotes the number of acquisition points and Te the period for sampling, for example, a frequency vector can be extracted by calculating a discrete Fourier transform:

P _m = _(m A1, A2 _m, _m ... Ai ... AN _m), where m denotes an index identifying a receiving transducer among M reception transducers used.

Preferably, N is less than 2000 and the acquisition frequency is greater than 400 kHz.

The vector P _m comprises all the amplitudes of the spectrum of the signal received at frequencies between Fe / N and the reception sampling frequency Fe, with a frequency step of 1 / T. Ai is the amplitude of the signal at a frequency Fi i Fc

checking the relation Fi =, for 1≤i≤N.

Finally, from the signals picked up by the reception transducers R1, R2 and sampled, it is possible to constitute an extended vector Pe = {Pi, ..., P _M } resulting from the fusion of the M vectors P _m .

As a variant, the vector or extended vector obtained may comprise only the amplitudes of the spectrum of the signal at frequencies between 20 kHz and 80 kHz.

Alternatively also, the vector or extended vector obtained may also contain only the amplitudes of Q predetermined frequencies.

Alternatively also, the extracted characteristics may comprise the phases of the signal obtained by Fourier transform.

STAGE OF LOCATION 200 During each location step 200, the measured vector, for example at least one of the vectors P _m , is compared with reference vectors of a set of reference vectors {P _m ref (x _u , y _v , z _w )} bijectively associated with a set of reference positions {(x _u , yv, z _w )} sampled on the surface of the touch plate 24 in a Cartesian coordinate system (u, v, w). The nearest reference vector (according to a predetermined distance) of the vector measured at the monitoring step 100 is selected and thus provides the coordinates of a touch.

The above notations relate to the detection of a single touch, but can easily be extended to the location of a multiple touch or, in other words, the location of k simultaneous touches (k> 1). More precisely, we deduce the k positions (x1, y1, z1, ..., xi, yi, zi, ..., xk, yk, zk) of k multiple touches associated with the measured vector P _m , of a search of the nearest reference vector (according to a predetermined distance) of this vector measured among a set of reference vectors {P _m ref (x _u i, y _v i, z _w i, ..., x _u ,, yv ,, z _wι , ..., x _Uk , y _v k, z _wk )} bijectively associated with a set of reference positions {(x _u i, y _v i, z _w i, ..., x _uι , y _vι , z _wι , ..., x _Uk , y _v k, z _wk )} sampled on the surface of the touch plate 24, in a Cartesian coordinate system (u, v, w).

The distance function used during this location step 200 can take various known forms.

It can be defined as the distance from Manhattan: d (P _m , P _m ref) = - Ai _m ref \,

or as Euclidean distance:

or as Minkowski's distance: where p is any integer,

or as distance from Chebyshev:

d (P _m , P _m ref) = Max (Ai _m - Ai _m ref).

It can have any other type of definition. In particular, if one chooses the amplitudes of the signal spectra received at the Q predetermined frequencies to build the measured vector, and if these amplitudes are centered and normalized, the distance calculation between the measured vector and the reference vectors is similar to calculating the cross-correlation function described in the aforementioned document WO 2008/142345.

In one embodiment of the invention, the distance chosen may be the one that gives the lowest location recognition error rate, this rate being evaluated during a prior step of testing the different distances on a control unit. random touches distributed on the touch surface.

In one embodiment of the invention, to validate the recognition of a single or multiple touch, the M receivers must all lead to identifying the same single or multiple position of the touch during the locating step by a search. minimum distance. The absence of simultaneous recognition on the M receivers is then sufficient to reject the position. This fusion of the measurements made by the M sensors is simple and does not require complex processing or particular synchronization.

Alternatively, the M receivers may have different degrees of priority. One can thus have a primary reception point and several secondary reception points. The secondary reception points then enrich the measurement of the primary reception point and lead to several measured vectors that can be merged into a single extended vector.

In one embodiment of the invention, a touch is detected and searched among the set of reference vectors if and only if the two following criteria are simultaneously checked:

the norm of the measured vector leaves a known stability range in the absence of touch, and

the norm of the vector measured falls within a range of possible variations of the standards of the set of reference vectors.

The stability range is defined by a variation noted in the absence of touch during a number of predetermined consecutive measurements. For example, the measured norm must deviate by more than 2% in absolute value from the average value of the norm observed over a hundred consecutive measurements to consider that one leaves the range of stability.

In one embodiment of the invention, the likelihood of the position identified for the single or multiple touch is tested on two or three consecutive measurements. If the consecutive measurements lead to the same position of a single or multiple touch then the identification is validated. Alternatively, to increase the reactivity of the locating step 200, the test may be more permissive and tolerate that only two or three measurements leading to the same position, out of a set of four or five consecutive measurements, be sufficient to validate a single or multiple touch location.

In one embodiment of the invention, the elastic mechanical wave is propagated from several different emission points. The consequence is that the reference set has a grouped average norm or has a range of dispersion of the vector norm P _m ref (x _u , y _v z _w ) less dependent on

(x _u , y _v z _w ).

Finally, in one embodiment of the invention, a touch plate 24 having a rather low reverberation constant, in particular less than 10 ms at 1 kHz and 1 ms at 70 kHz, is chosen, which makes it possible to have a clock rate of high measurement. This reverberation constant is defined as the period after which the residual signal following a pulse in the plate only represents 36% of the initial signal, ie a damping equivalent to 1 / exp (1).

As previously seen, the locating step comprises comparing at least one measured vector with a set of reference vectors. This set of reference vectors can be constructed during a preliminary learning step which will now be detailed.

This preliminary learning step can be carried out either for each individual touch plate or for a standard touch panel representative of a series of touch plates having the same dimensions, the same transducers bonded to the same positions and in the same way, the plates being they themselves integrated in the same way to a frame forming a support. The excitation of waves at frequencies other than the resonance frequencies is then an advantage because, even in the case where the plates may appear identical, there may be small variations, for example the presence of air bubbles or a variation in thickness of the glue, responsible for a dispersion of the resonant frequencies for a series of plates supposed to be identical.

The preliminary learning step is performed as the monitoring step 100 described above, but under predetermined conditions of single or multiple touches to obtain the aforementioned reference vectors, then used in the localization steps in use. normal touch-screen device.

During this preliminary learning step, it is possible to determine the reference vectors of simple touches {P _m ref (x _u , y _v z _w )} or multiples {P _m ref (x _u1 , y _v1 , z _w1 , ..., x _uι , y _v ,, z _wι , ..., x _Uk , y _v k, z _wk )} in the same way that we determine the vector P _m in the monitoring step 100. These values, {P _m ref (x _u , y _v z _w )} or {P _m ref (X _u , y _v i, Z wi, ..., X _u , y _v ,, z _w ,, - -, x _U k, y _v k, z _wk )}, correspond to amplitudes of frequencies of spectra of signals picked up when there are one or more (k) touches on the touch plate 24, at predetermined locations of coordinates {(x _u , y _v z _w )} (single locations) or {(x _u i, y _v i, z _w1 , ..., x _u ,, yv ,, z _{w i} , ..., x _Uk , y _v k, z _wk )} (multiple locations) sampled on the touch plate, (u, v, w) being indicia relating to the possible positions of a touch on the touch plate 24 expressed in a three-dimensional landmark.

The single or multiple reference touches may come from one or more artificial fingers, stylets, or fingers of a user.

In the case of a tactile surface divided into a grid of 9χ9 discretized locations, one will need 81 reference vectors for the localization of a simple touch. For the localization of a double touch, we will need

C ^ ₁ = 3240 reference vectors. More generally, for the location of k simultaneous touches (a priori these touches are identical and permutable) on a UxV sampling grid discretized locations, the necessary number of reference vectors is the number of combinations of k elements among a set of UxV elements be C _m ^k _v .

According to one embodiment of the invention, to have a more reliable final location, it is possible to repeat a certain number of times the preliminary step of learning a single or multiple touch on a predetermined single or multiple position and not to retain than an average value. In particular, it is possible, for example, to retain only the average value over ten identical learnings.

The set of reference vectors is thus constructed by an average of S successive acquisitions for each reference position (S = 10 for example), with a certain standard deviation. Each reference vector can then take the form of a complex vector comprising, for each of its coefficients, a real part indicating an average damping at the frequency considered and an imaginary part indicating the standard deviation:

P _m ref = ((A1 _m , σ1 _m ), ... (Ai _m , σi _m ), ... (AN _m , σN _m )).

According to one embodiment of the invention, it is possible to use several sets of reference vectors each corresponding to a multiplicity k of touches. In particular, it is possible to provide k sets of reference vectors each having C _V ^k _xV reference vectors when the number of simultaneous interpretable touches can reach k.

It is then also possible to unite these sets into a single reference set in which the reference vectors are ordered by increasing standard vectors. By thus ordering the reference vectors in the reference set, it becomes possible to accelerate the step of finding the reference vector closest to the measured vector, preselecting for example a limited range of possible standards in the set. reference in a predetermined neighborhood of the norm of the measured vector. The search is thus truncated to a reference subset. In addition, the norm of the measured vector is indicative of the state of the coupling of the tactile surface with its environment: in particular, one or more simultaneous touches on the tactile surface generates (s) a variation of the norm of the measured vector, of so that it is strongly correlated with the number k of simultaneous touches.

According to a second aspect of the invention, the electronic central unit of the device described above is furthermore designed to:

defining at least one simple or multiple trace from a plurality of touches located successively on the tactile surface, and

interpreting this simple or multiple plot by comparing certain features of this plot with a set of features identifying single or multiple reference plots.

More precisely, as indicated with reference to FIG. 1, for a succession of single or multiple touches detected on the touch plate 24, forming a single or multiple trace 26, a location of this trace 26 can be visualized on the microphone screen. -computer 12, in the form of a kinematic curve 28 obtained by interpolation of the pattern 26 detected. The location of a single or multiple touch comprises a set of steps whose total duration is less than 10 ms, or even 5 ms, and constitutes a continuous looping process so that the measurement rate can be high. and obtaining a simple or multiple easy route.

The kinematic curve 28 may also consist of several segments, the last point of a segment and the first point of the next segment being characterized by a contact break with the touch plate 24 for a predefined minimum time, for example between 50 ms and 150 ms. The interpretation of successive single or multiple touches makes it possible, for example, to design an object with a tactile surface capable of:

- to sample a moving touch (i.e. a plot),

- calculate the speed and acceleration of a moving touch,

- measure the standard of a touch and establish a correspondence between this standard and the force of touch,

- identify the beginning of a touch, the end of a touch,

- draw a kinematic curve by interpolation of the plot,

- Establish signatures of dynamic interactions with the tactile surface, such as interactions relating to a caress, a hit "single click", a hit "double click", whether for a single touch or multiple,

- designate, move graphic objects from a computer operating system (for example a computer-aided design drawing, a photograph, a document, etc.) into a computer workspace (for example the screen 14 or 24)

- designate, move, orient an object in a virtual space according to a direction of movement of the touch,

- interpreting a touch according to its single or multiple plot, its speed, its acceleration, to perform a function according to a predetermined sign language (fast forward, fast rewind, selection, zoom in, zoom out, rotation, free deformation to from k deformation points, ...).

FIG. 7 illustrates the successive steps of an example of a logical method for interpreting at least one touch on a tactile surface of an object, according to the second aspect of the invention.

This method firstly comprises the execution of several successive location steps 200 leading to the determination of a single or multiple plot by the electronic central unit.

Then, during a test step 300, it is determined whether the plot to be interpreted is simple or multiple. If it is a simple plot, it passes depending on the context and characteristics of the route at one of the steps 302, 304 or 306.

During step 302, in a context of viewing an object in a virtual and / or working space, a simple plot such as one of the traces bearing the reference 50 in FIG. 8 is interpreted as a command traveling from this object, especially if the initial touch of the plot points to the object in question. The plots illustrated in Figure 8 are plots (taken as simple examples) of moving to the right, to the left, to the top or to the bottom, the white point indicating the starting position (beginning of the plot) and the gray dot indicating the finish position (end of course).

During step 304, in a context of viewing an object in a virtual space and / or work or in a context of a list of any objects, a simple layout such as one of plots bearing reference numeral 52 in Fig. 8 is interpreted as an acceleration control of the displacement of the displayed object or as an advance or rewind command in the presented list. In this context, not only the direction of the plot, but also its speed and / or acceleration are taken into account: thus, a right-pointing and acceleration-oriented plot is interpreted as a fast-return while a course-oriented plot the left and undergoing acceleration is interpreted as a fast forward.

In step 306, in a context of reading a multi-page document, a simple plot such as one of the traces bearing the reference 54 in FIG. 8 is interpreted as a return command on the previous page. or go to the next page. In this context also, not only the direction of the plot, but also its speed and / or acceleration are taken into account: thus, a quarter-circle plot followed by a rectilinear acceleration at the end of the plot is interpreted as a change of page, to the next or previous page depending on the orientation of the path.

If during step 300 it is determined that the plot to be interpreted is multiple, it goes to another test step 400 determining whether the plot is double or is more than two simultaneous touches. If it is a double plot, we move according to the context and characteristics of the route at one of the 402 or 404 steps.

During step 402, in a context of viewing an object in a virtual and / or working space, a double trace such as one of the traces bearing the reference 56 in FIG. 9 is interpreted as a command to zoom in or out of this object, especially if the initial double touch of the plot points to the object in question. The zoom range is determined by the variation in the distance between the two simultaneous touches during the course of the plot. Conventionally, this zoom function is interpreted and displayed as a command for homothetic deformation of the object displayed. During step 404, in a context of viewing an object in a virtual and / or working space, a double semicircle trace such as one of the traces bearing the reference 58 in FIG. 9 is interpreted as a rotation command of this object, especially if the initial double touch of the plot points to the object in question.

If during step 400 it is determined that the plot to be interpreted is more than two simultaneous touches, it proceeds to a step 500 of interpreting a path with simultaneous touches at least triple. In one embodiment of the invention, a step 502 of free deformation of the object is then carried out.

During this step 502, in a context of visualization of an object in a virtual and / or working space, an at least triple plot such as the plot bearing the reference 60 in FIG. 9 is interpreted as a deformation command. free of the object. In particular, the path 60 is triple: it points, for example, initially to three points of the object, and the displacement of these three respective points along the triple path defines a vectorial deformation that must be applied to the object.

Following steps 302, 304, 306, 402, 404 and 502, a step 600 of executing the aforementioned interpreted functions and displaying their result, for example on screen 14 (the case of FIG. 1), is carried out or 24 (case of Figure 2).

Note finally that the second aspect of the invention, described with reference to Figures 7, 8, 9 and relating to the interpretation of a detected single or multiple touch, although advantageously combined with the first aspect described with reference to Figures 1 to 6, is independent of it in the sense that any other method of single or multiple location of a touch or a plot (as a succession of touches) could be used for the implementation of the interpretation of touch.

It is clear that a method for locating at least one touch on a tactile surface such as that described above makes it possible to achieve a treatment time that is significantly lower than conventional methods by analyzing the possibility of single or multiple touching as soon as the phase transient propagation of elastic mechanical waves in the tactile surface by analyzing the effect of these touches on the radiation and / or illumination of the tactile surface. Specifically, where conventional methods imposed an acquisition time of up to 50 ms, it is divided by a factor of about ten. It is thus possible to carry out a large number of measurements per second and to determine compatible traces. with the classic function of making a "drag and drop".

The processing is also simple enough to be implemented in commercial microcontrollers.

In addition, this method is not dependent on the eigenfrequencies of the touch-surface object and therefore does not need to be very selective or stable in the frequencies studied. In particular, it does not require activating the resonant frequencies of the object when the thickness of the object is very small compared to the wavelength of the waves emitted and the characteristic dimension of a finger. It is therefore compatible with tactile plates that are thin (less than one millimeter) and strongly damped, as can be the case of the top plate (user side) of a liquid crystal display or a plastic shell. Moreover, this leaves a much larger choice of usable frequencies for the analysis of the figures of radiation and / or illumination.

Another advantage is to be able to obtain satisfactory results, for example millimetric localization accuracy, from a limited number of transmitters and sensors. In particular, at least a single transducer, successively transmitter and receiver, may suffice. Two emitters and two receivers arranged unsymmetrically at the periphery of the tactile surface provide very good estimates. In addition, these transmitters / receivers may be small, in particular only a few square millimeters.

As has been seen previously, it is also possible to discriminate a single touch and a multiple touch.

Another advantage is also to be able to integrate the touch plate in a frame using fixing points (in particular by gluing) which participate (without harming) in the construction of discriminating radiation patterns and / or illumination.

We have also seen that the invention is not limited to flat glass surfaces, but also applies to curved surfaces and plastic or metal shells, which multiplies the possible applications. This is all the more true that the method as described above takes advantage of tactile surfaces with complex and irregular contours for the formation of radiation and illuminations discriminating according to the touch.

Finally, according to the second aspect of the invention, the method described above makes it possible to create a tactile language or gesture interpretable in commands functional computer as well as a keyboard shortcut, but in a more intuitive way.

Some possible industrial applications of the devices and method described above include, but are not limited to:

- multi-touch touch-screen displays for game consoles, mobile phones, personal digital assistants and LCD screens, in the context of a man-machine interface with dynamic interpretation of single or multiple touch,

- flat or curved tactile keyboards, touch control buttons on objects of complex shapes,

- The tactile hulls for robots able to perceive various touches such as caresses, blows, etc.

Note also that the invention is not limited to the embodiment described above. It will be apparent to those skilled in the art that various modifications can be made to the embodiment described above, in the light of the teaching that has just been disclosed. In the following claims, the terms used are not to be construed as limiting the claims to the embodiment set forth in this description, but must be interpreted to include all the equivalents that the claims are intended to cover by reason 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

A method of locating at least one touch on a touch surface (24) of an object (10; 30), comprising the steps of:

- monitoring (100) at least one touch by propagation (102), in the tactile surface of the object, elastic mechanical waves from at least one emission point (E1, E2) of the object, and by detecting said elastic mechanical waves in at least one receiving point (R1, R2) of the object to obtain at least one sensed signal, and - locating (200) at least one touch on the touch surface of the object by comparing certain spectral characteristics of the sensed signal to a set of reference characteristics, characterized in that the monitoring step (100) comprises a measurement (104, 106) of the signal picked up during a starting time interval ( t ₃ ) during a transient phase of the transmitted wave propagation, for the supply of radiation information, disturbed by said at least one touch, to said at least one reception point (R1, R2).

2. A method of locating at least one touch on a touch surface according to claim 1, wherein the measurement (104, 106) of the sensed signal is prolonged (t ₄ ) beyond the establishment (ti) of a stationary phase of transmitted wave propagation, for providing illumination information to said at least one reception point (R1, R2).

A method of locating at least one touch on a touch surface according to claim 1 or 2, wherein said reference characteristics correspond respectively to single and multiple touches at predetermined areas of the touch surface.

4. A method of locating at least one touch on a touch surface according to any one of claims 1 to 3, wherein the transmitted waves comprise a plurality of predetermined frequency components all distinct from the vibratory eigenfrequencies of the object.

5. A method of locating at least one touch on a touch surface according to claim 4, wherein each frequency component of the transmitted waves is chosen so as to be at a frequency distance of more than twice the width of a peak. resonance energy corresponding to any vibratory natural frequency of the object.

6. A method of locating at least one touch on a touch surface according to claim 4 or 5, wherein the characteristics of the sensed signal compared to the reference characteristics are spectral amplitudes of the signal captured at said predetermined frequency components forming a vector said " measured "and the set of reference features comprises a set of reference vectors each associated with a single or multiple touch, this reference set being constructed during a prior learning step, similar to the monitoring step , in which different single and multiple reference touches are measured.

A method of locating at least one touch on a touch surface according to claim 6, wherein, the reference vectors being ordered in the reference set according to the value of their standard, the locating step (200) includes the following substeps:

- calculation of the norm of the vector measured,

selecting a subset of the reference set representing a range of norms in a predetermined neighborhood of the norm of the measured vector, and

8. Device (10; 30) for locating at least one touch on a touch surface (24) of an object (18; 30), comprising at least one transducer (E1, E2, R1, R2) designed to emit and sensing elastic mechanical waves propagating in the tactile surface of the object, and an electronic central unit (12, 32), connected to said at least one transducer, programmed to:

characterized in that the electronic central unit (12, 32) is further programmed to measure the signal picked up during a time interval beginning during a transient phase of transmitted wave propagation, for the provision of a radiation information, disturbed by said at least one touch, said at least one receiving point.

A device for locating at least one touch on a touch surface according to claim 8, further comprising the object (30), its touch surface (24) and means (P) for holding the touch surface on the touch screen. object disposed at neighborhoods of convex zones of discontinuity of the periphery of the tactile surface.

A device for locating at least one touch on a touch surface according to claim 8 or 9, wherein the electronic central unit (12, 32) is further adapted to:

- defining at least one simple or multiple pattern (26; 50, 52, 54, 56, 58,

60) from a plurality of touches successively located on the touch surface (24),

interpreting this single or multiple plot (26; 50; 52; 54; 56; 58; 60) as a predetermined function to be performed by comparing certain features of that plot to a set of reference features.