WO2012114008A1

WO2012114008A1 - Capacitive gestural interface with measurement mode switching

Info

Publication number: WO2012114008A1
Application number: PCT/FR2012/050182
Authority: WO
Inventors: Christophe BLONDIN; Christian Neel; Didier Roziere
Original assignee: Nanotec Solution
Priority date: 2011-02-21
Filing date: 2012-01-30
Publication date: 2012-08-30
Also published as: FR2971867B1; FR2971867A1; EP2678763A1

Abstract

The invention relates to a control-interface device, including : (i) a plurality of capacitive electrodes arranged so as to cover a detection surface; (ii) an electronic capacitive-measurement means capable of producing information on a distance and/or contact between at least one control object and capacitive electrodes; and (iii) a switching means capable of configuring said electronic capacitive-measurement means so as to enable direct capacitance measurements, as well as measurements of the variation in coupling capacitances. The electronic capacitive-measurement means at least partially references a floating reference electrical potential during the direct capacitance measurements. The invention also relates to a method implemented in said device or in an apparatus.

Description

«Capacitive gesture interface with measurement mode switching»

Technical area

The present invention relates to a control interface device responsive to movement and / or in contact with at least one control object, such as a gesture interface.

The field of the invention is more particularly but in a nonlimiting manner that of capacitive touch and capacitive proximity surfaces used in particular for HMI commands.

State of the art

A large number of tactile and gestural interfaces use capacitive technologies. The touch surface is equipped with conductive electrodes connected to electronic means which make it possible to measure the variation of the capacitances appearing between electrodes and the object to be detected in order to carry out a command.

This object, or control object, can be for example a finger or a stylus.

Capacitive techniques currently implemented in touch interfaces most often use two layers of conductive electrodes in the form of rows and columns. Electronics measure the coupling capabilities that exist between these lines and columns. When a finger is very close to the active surface, the coupling capabilities near the finger are modified and the electronics can thus locate the position in 2D (XY), in the plane of the active surface.

These technologies based on coupling capacity measurements are often called in English "mutual capacitance". They make it possible to detect the presence and the position of a finger through a dielectric of small thickness. They have the advantage of allowing a very good resolution for the location in the plane (XY) of the sensitive surface of one or more fingers or other control objects. They also allow with appropriate processing software to manage a large number of control objects if the surface of the interface is large enough.

These techniques, however, have the disadvantage of generating, in principle, significant leakage capacitances at the level of the measuring electrodes and electronics. Indeed the detection of a finger is performed by measuring the variation of the coupling capacitance created between each row and column, one of which emits an electrical signal and the other receiver of the signal to be detected. This signal is proportional to the capacity between the selected rows and columns. When a finger is very close to the intersection of the line and column pair concerned, the coupling capacity is reduced and finger detection is performed.

These important coupling capabilities - even without the presence of the object to be detected - can further drift over time due to aging, deformation of the materials, or the effect of the variation of the surrounding temperature. These variations can degrade the sensitivity of the electrodes, or even trigger orders untimely. This is one of the reasons why these technologies can not detect more often than the contact of the control objects and not their approach because it is necessary to create large variations of capacity, much higher than the drifts, to avoid any detection artefact .

Techniques are also known for measuring the capacitance that appears between electrodes distributed for example on an active surface and an object to be detected. The electrodes are scanned sequentially by a measurement electronics which determines the capacitance, and therefore distance information, between the electrodes and the object (s) to be detected. These so-called direct capacity measurement techniques are often called in English "self capacitance".

These direct capacitance measurement techniques are well suited to capacitive control interfaces requiring few electrodes, such as interfaces whose active surface is of relatively small size. On the other hand, for larger sensitive surfaces, the number of electrodes necessary to cover the entire surface generally becomes too great to be able to be managed with reasonable reaction times by a miniature electronic circuit.

It is also possible to use electrodes in line and column structure with direct capacitance measurement techniques. The electrodes in rows and columns are then used as independent electrodes and allow a measurement without contact or gesture at great distance (detection of a finger to several centimeters). However, another problem occurs when you want to detect more than one object. Indeed, the measurement requires the scanning of each line and each column, resulting in the appearance in the measure of virtual objects called ghosts. These ghosts prevent the absolute location of several objects on the sensitive surface.

To detect multiple objects remotely (in 3D), the ideal would be a solution that would keep on the same system the advantages of the two principles of direct capacitance measurement for the detection of proximity and measurement of mutual capacitance capabilities to detect multiple objects without ghosts.

Document US 2010/0328262 to Huang et al. which discloses a capacitive interface device for operating in the two modes of direct measurement of capacitance or measurement of coupling capabilities ("self capacitance" or "mutual capacitance") and switching between the two. Switching to coupling capability measurement mode is used precisely to remove ghost ambiguity when two objects are detected.

Due to the detection technology used, the device is however limited to contact measurements. In addition, the presence of crossed electrodes greatly disrupts the measurements in the direct capacitance measurement mode, since the coupling capacities between tracks remain present and become parasitic capacitances which are compensated electronically, with all the risks of drift and electronic noise. that entails.

US2011 / 0007021 is also known from Bernstein et al. which discloses a capacitive interface capable of detecting a finger in proximity or on a sensitive surface. The device comprises an array of row and column electrodes that can operate in a direct capacity measurement mode and a coupling capacity measurement mode. The scope of the device is improved by the use of a guard electrode subjected to an alternating potential.

The use of such an active guard is a well-known technique in capacitive metrology for decreasing the parasitic capacitances and consequently improving the measurement sensitivity. But this technique alone is not sufficient to allow measurements at great distances. Also known is the document FR 2 844 349 Rozière which discloses a capacitive proximity sensor comprising a plurality of independent electrodes, which allows to measure the capacitance and the distance between the electrodes and an object nearby.

This technique achieves large ranges or measurement ranges, while allowing accurate distance measurements. These results are achieved thanks to the use of a floating detection electronics which makes it possible to keep the measurement and guard electrodes at the same floating potential with respect to the earth, and to eliminate parasitic coupling capacitors. This floating detection electronics is described in detail in document FR 2 756 048 of Rozière.

The aim of the present invention is to propose a solution that makes it possible to manage capacitive electrodes in direct capacitance measurement and coupling capacity measurement modes with the same electronic circuit, while guaranteeing optimal performances in terms of sensitivity of the capacitors. detection and accuracy for remote measurements, as well as resolution.

Presentation of the invention

This objective is achieved with a control interface device comprising:

a detection surface,

a plurality of capacitive electrodes arranged so as to substantially cover said detection surface,

capacitive electronic capacitance means capable of producing distance and / or contact information between at least one control object and capacitive electrodes,

switching means capable of configuring said capacitive measurement electronic means so as to allow either direct capacitance measurements between capacitive electrodes and one or more control objects, and measurements of variation of coupling capacitors between capacitive electrodes for excitation and measurement,

characterized in that said capacitive electronic capacitance means are at least partially referenced to a floating reference electrical potential with respect to a ground potential in direct capacitance measurements. Preferably, the floating potential is an alternating potential. It is said to be floating with respect to a ground potential since it is not referenced (electrically) at this ground potential, or to the extent that it is variable (definite or indefinite) with respect to ground potential. to this mass potential.

The ground potential may be the ground of the device, or a ground, or any potential referenced electrically to a mass of the device, but possibly different from it.

The control objects may be for example a finger or a stylus. An action performed by a user with two or more fingers is thus "seen" by the device as the action of several control objects. These control objects can, without loss of generality, be considered as referenced to the device ground or to the ground.

The use of a detection circuit with a floating electric potential makes it possible to eliminate the parasitic coupling capacitors between elements that "float" all electrically at the same voltage, and thus to obtain a sensitivity and a precision of measure unreachable with a detection circuit referenced to the ground. This allows for precise detection of control objects at large distances.

According to one embodiment or configuration of the device according to the invention, the capacitive measuring means can be referenced to a reference electrical potential fixed with respect to the ground potential during measurements of coupling capacitors.

This reference electric potential can also be equal to the ground potential or referenced to a ground potential. In this case, the coupling capacity measurement mode operates according to a more conventional scheme but sufficient to detect contacts between control objects and the detection surface for example.

According to another embodiment or configuration of the device according to the invention, the capacitive measuring means can at least partly be referenced to a floating reference electric potential with respect to the ground potential when measuring coupling capacitors.

In this case, the capacitive measuring means comprise a part referenced to a reference electrical potential floating in the two modes. measurement (direct capacity measurements and coupling capacity measurements).

The device according to the invention may furthermore comprise switching means arranged in such a way as to connect at least one excitation capacitive electrode to a fixed electrical potential with respect to the ground potential during coupling capacitance measurements.

In this case, with a detection part referenced to a floating reference electric potential, a control object and the excitation electrodes are "seen" by the floating detection as substantially grounded elements, whose coupling capacitors are measured. in parallel on the measuring electrode. This gives a better sensitivity and a better range of detection in this mode of coupling capacity measurements.

The device according to the invention may further comprise switching means arranged so as to allow a change of reference electrical potential, between a floating potential and a fixed potential with respect to the ground potential.

The invention makes it possible to implement floating detection electronics which are particularly effective for long-range measurements, and to advantageously combine it with coupling capacity detection modes which allow unambiguous detection of several short-range control objects. .

The invention thus extends the field of application of this measurement technique by floating detection, one of the objectives as described in the prior art is precisely to eliminate the coupling capacitors between neighboring electrodes or between the electrodes and the electrodes. 'environment.

In addition, the invention describes a mode of implementation of a floating detection for measurements of original coupling capabilities in view of the prior art.

Finally, it should be noted that the different configurations of the invention can be implemented in the same device, with switching means such as switches or analog switches to switch from one configuration to another. Of course, a device according to the invention may also be made so as to implement only part of the possible modes of operation.

The device according to the invention may further comprise a guard electrode at an electrical reference potential disposed near the capacitive electrodes, according to their face opposite to the detection surface.

According to the configurations, this guard electrode may be at the floating potential or at the fixed potential with respect to the ground potential. It makes it possible to overcome to a large extent disturbances to the environment, in particular those due to the device comprising the interface.

The device according to the invention may further comprise scanning means for:

- during direct capacitance measurements, to select at least one measuring capacitive electrode so as to allow measurements of capacitance between this or these measurement electrode (s) and the control object (s),

during the coupling capacitance measurements, selecting at least one excitation capacitive electrode and at least one measuring capacitive electrode, so as to enable measurements of coupling capacitance variation between said capacitive excitation electrodes and measured,

connecting the non-selected capacitive electrodes to the reference potential.

Thus, the unselected electrodes contribute to the guard, which allows in particular in the direct measurement mode of capacity to cancel parasitic capacitances and to optimize the sensitivity.

According to embodiments, the device according to the invention may further comprise:

capacitive electrodes arranged substantially in two crossed directions;

capacitive electrodes arranged in two superposed layers, which layers comprise, respectively, electrodes in a first direction and electrodes in a second direction; capacitive electrodes arranged in a layer, said electrodes comprising elements connected by bridge connections in a first direction and a second direction, respectively;

capacitive electrodes arranged along rows and columns; capacitive electrodes comprising a plurality of surfaces electrically connected to one another, which surfaces may be substantially of one of the following shapes: square, rectangular, diamond-shaped, circular, elliptical;

substantially transparent electrodes based on ITO ("Indium Tin Oxide").

According to a variant, the device according to the invention can comprise:

independent capacitive measuring electrodes, distributed along the detection surface and connected to scanning means,

a capacitive excitation electrode arranged in such a way as to substantially surround the capacitive measuring electrodes.

The capacitive excitation electrode may be disposed on the same surface or on a surface substantially parallel to that of the measuring capacitive electrodes.

The sensitive surface is thus substantially covered with multiplexed independent measuring electrodes, which can be used in the two direct capacitance measurement and coupling capacity measurement modes.

In the direct capacitance measurement mode, the excitation electrode (s) are not used and are put to the potential of the guard to which they contribute.

Coupling capacitance measurements are made between the excitation electrode (s) and measuring electrodes, for example by measuring electrode measurement.

With a sensitive surface sampled by independent measuring electrodes, there is in principle no problem of ghosts, contrary for example to electrodes in rows and columns. However, the use of a coupling capacity measurement mode as described makes it possible to substantially improve the short-distance lateral resolution and thus to better discriminate near control objects. In another aspect, there is provided a control interface control method implementing a device according to one of the preceding claims, comprising steps of:

configuration of the capacitive electronic measurement means so as to allow direct measurements of capacitance,

- scanning measuring electrodes to detect supposed control objects,

if a plurality of control objects is detected, configuration of the capacitive electronic measurement means so as to allow measurements of variation of coupling capacitors,

scanning of the capacitive excitation and measurement electrodes whose coupling regions are in or near areas of the measuring surface in which supposed control objects have been detected, to determine movements and / or contacts of control objects.

Description of the Figures and Embodiments

Other advantages and particularities of the invention will appear on reading the detailed description of implementations and non-limiting embodiments, and the following appended drawings:

FIG. 1 shows a diagram of the device configured according to a direct capacity measurement mode, with a floating reference electric potential,

FIG. 2 shows a diagram of the device configured according to a coupling capacity measurement mode, with a floating reference electric potential,

FIG. 3 shows a diagram of the device configured according to a coupling capacity measurement mode, with a reference electrical potential fixed with respect to the ground potential.

FIG. 4 shows alternative embodiments of the capacitive electrodes, with capacitive measurement electrodes that are independent over the entire surface and, FIG. 4 (a) and FIG. 4 (b), an excitation electrode and FIG. 4 (c). ) columns of excitation electrodes.

An exemplary embodiment of a device according to the invention, which of course is not limiting, will be described with reference to FIGS. 1, 2 and 3.

The device comprises a detection surface 1. Two crossed electrode layers 3, 4 are placed on superimposed surfaces, rows and in columns, therefore in two substantially perpendicular d irections. A guard electrode 2 is placed behind the electrodes 3, 4, that is to say on their side opposite to the detection surface 1. This guard electrode 2 makes it possible to avoid capacitive leaks during capacitance measurements and greatly reduce parasitic coupling capacitances in coupling capacity measurement mode.

The device according to the invention can operate according to a capacity measurement mode, in which capacitances (or at least information relating to capacitances, which may also be for example capacity reversals) are measured 1 / C) between one or more control objects and electrodes 3, 4, for the purpose of deriving the distance or approach information. The detection electronics is configured in floating mode. This mode is shiny in Figure 1.

The device can also operate according to coupling capacitance measurement modes, in which a variation of coupling capacitance between excitation electrodes 3 and measuring electrodes 4 is measured (or at least information relating to a capacitance). which may also be, for example, an inverse of capacitance 1 / C) sufficiently close to at least one area of the detection surface 1 to interact capacitively. In these modes, an object of control is detected by the disturbances of the capacitive coupling that it generates when it approaches the zone where the electrodes 3, 4 interact.

The device according to the invention can operate according to two modes of coupling capacity measurement:

in a first mode it shines in FIG. 2, the detection electronics is a floating electronics, referenced to a floating potential;

- In a second mode it shines in Fig ure 3, the detection electronics is an electronic referenced to a fixed potential with respect to the mass of the ispositif device.

Of course, it is not necessarily necessary in practice to implement the two modes of coupling capacity measurement on the same ispositif.

The device comprises the same components in all modes. A set of analog switches SI ... S13 allows you to switch from a configuration allowing measurements of capacity to Coupling capacity measurement configurations. These switches S1 ... S13 are chosen so as to minimize all the parasitic capacitances that they are capable of generating.

Advantageously, the invention allows a high speed of detection of one or more control objects (or others). It is known that contactless control applications must be simple so that anyone can easily master gesture commands. Indeed, because it does not touch the control surface or detection 1, it is more difficult to control the movement of one or more fingers.

The most common non-contact commands are approach detection to activate a device, move an image on a screen, magnify or reduce an image .... These commands can be performed with one or two fingers. These commands can be detected with the invention by taking measurements along lines 3 and columns 4 of sensors in the direct capacity measurement mode. This technique is fast because it is sufficient to select sequentially at most all n rows and m columns, which represents n + m measures.

On the other hand, to perform more complex commands with at least two fingers or to detect their real positions, it is necessary to use a coupling capacity measurement mode because the direct capacity measurement mode would generate ghosts that make these commands impossible. to interpret correctly.

Coupling capability measurement modes normally require sequential selection of all coupling capabilities, i.e., all row-column nodes, which represents n x m combinations. It is possible to significantly reduce the number of combinations by exploiting the areas where the fingers and ghosts were previously identified in the direct capacity measurement mode.

Under these conditions, the position detection of several fingers can be performed with a number of measurements between n + m and n x m.

The invention is more particularly suited to medium and large size touch screens where the approach detection function of one or more fingers, or one or more hands, becomes possible using a number of electrodes 3, 4 limited, while maintaining the touch and multi-touch function that exists on the market. The capacitive electrodes 3, 4 and the guard electrode 2 may be made of transparent conductive material as deposited on a polymer such as PET or on glass so that they can be used on screens.

The rows and columns of electrodes 3, 4 comprise a succession of surfaces in the form of a square or rhombus. The distance separating these emitting and receiving surfaces can be advantageously optimized in order to optimize the range of the distance measurement with respect to the detection surface 1.

Indeed, in coupling capacity measurement mode, the measurement has a fairly low sensitivity and the scope of the detection of the control object is limited to a few millimeters in the air. However, thanks to the presence of the guard 2 and a slight air gap between the emitter 3 and receiver 4 electrodes, it is possible to increase the sensitivity when approaching the object. This technique makes it possible to project the field lines emitted by the emitting electrodes 4 a little further and to react earlier when approaching an object. It is thus possible to detect a finger in coupling capacity measuring mode more than 5 mm apart.

The rows and the columns of electrodes 3, 4 can be completed towards the edges of the detection surface 1 by a last electrode substantially in the shape of a triangle to improve the detection capabilities of the device towards the edges.

In the direct capacity measurement mode of FIG. 1, the measured capacitance increases as the object to be detected approaches. The capacities to be measured in this case are generally between some femtofarads and some picofarads.

In the floating electronics-based coupling capacitance measurement mode of FIG. 2, the measured capacitance also increases as the object to be detected approaches, since this object and the excitation electrodes 3 are substantially at ground potential. Mr.

In the ground-referenced electron-based coupling capacitance measurement mode of FIG. 3, the object to be detected acts as a ground-disturbing element that derives a portion of the field lines between the excitation electrode. 3 and the measuring electrode 4 and therefore decreases the coupling capacity when approaching. The capacitances to be measured in coupling capacity measurement modes are generally between a few picofarads and a few tenths of picofarads.

The electronics 8 is designed to be able to measure both the capacitances in direct capacitance measurement mode and the coupling capacitance measurement mode.

The choice of coupling capacity measurement mode (floating or non-floating) depends on the application. The floating mode of FIG. 2 allows a better sensitivity to detect control objects, whereas in some cases, according to the electrode geometries, the non-floating mode of FIG. 3 allows a better lateral resolution.

The device shown in FIGS. 1, 2 and 3 comprises, in a nonlimiting manner, four electrode lines 3 which can be used as single electrodes in direct capacitance measurement mode and as emitting or excitation electrodes in the measurement mode of the electrodes. coupling capacitors, and four electrode columns 4 which can be used as single electrodes in direct capacitance measurement mode and in receiver or measurement electrodes in the coupling capacitance measurement mode.

The electronics used are a so-called floating-feed electronics for the direct capacitance measurement mode, shown in FIG. 1, as well as for the coupling capacitance measurement mode shown in FIG. Switching switches S1 ... S13, this electronics is transformed into non-floating electronics in order to operate in the coupling capacity measurement mode shown in Figure 3.

In floating mode, the electronics energize the electrodes 3, 4 concerned and keep them 9 preferably at a fixed frequency, with respect to the mass M. The mass M has a potential close to that of the earth and the earth. object to be detected (external environment).

The electrodes are protected by a guard electrode 2 connected to the potential of the guard 9.

The rows and columns of measuring electrodes 3, 4 and the guard electrode 2 are connected to the electronic circuit 8 by means of conductive tracks 7, for example made of copper or silver. In order to minimize capacitive leakage, the connection tracks between the electrodes 3, 4 and the electronics 8 are shielded with the shielding B1 is connected to the potential of the guard 9. This connection can be realized with a cable, or preferably with a multilayered substrate, such as for example a polyimide-based (Kapton) or PET-based bulk circuit.

The tracks connected to the electrodes 4 which have only the receiver function are slightly elongated from the tracks connected to the electrodes 3 having the two transmitting and receiving functions in order to limit the capacitive leaks in the coupling capacitance measurement mode. The use of flexible floss promotes this protection thanks to the small air gap between tracks 7 and the guard plan.

The operating principle of the management of the electrodes 3, 4 will now be described, making it possible to implement the capacitance measurement and capacitance measurement modes while minimizing the parasitic capacitances.

In the capacity measurement mode of FIG. 1, the measurement electrodes 3, 4 are all receivers. The switches S1 through S8 selectively select the measurement receiving electrode (or the active electrode) 3, 4. The non-selected receiving electrodes for each sequential measurement are connected to the guard 9 to prevent capacitive leakage.

The switches S9 and S10 are connected to the floating reference or guard potential 9 in order to avoid capacitive leakage with the excitation potential generated by the oscillator OSC. The oscillator OSC preferably provides a fixed frequency electrical voltage.

Switches SU and S12 connect the electrodes of the lines 3 to the charge amplifier A, which makes it possible to measure the capacitance between the active electrode and the object or objects.

The switch 13 relays the output of the oscillator OSC to the external mass M and thus provides the excitation of this mass M in order to set the excitation voltage of the electrodes 3, 4 and floating capacitive bridge. The entire floating electron is powered by an AF floating power supply.

The configuration of the electronics implemented in this mode, also called floating bridge, is described in document FR 2 844 349 Rozière. Several embodiments are applicable to the invention, particularly based on measurements of capacitance C or inverse capacity 1 / C. They are described in detail in document FR 2 756 048 of Rozière and are therefore not repeated here.

This floating bridge electronics makes it possible to eliminate parasitic capacitances to a large extent. Thus, the measured capacities are directly those created between the target object and the electrodes 3, 4. The sensitivity of the device is optimized and allows a very long-range measurement very resolute. In addition, the capacitive sensors and the associated electronics can then be optimized to reach a measurement range, or dynamic, important. Indeed, the range of capacitances to be measured with each electrode can range from less than one thousandth of picofarad to several picofarads, ie a dynamic in terms of capacity greater than 1000. This dynamic makes it possible to detect, with substantially the same resolution side related to the size of the electrode, the presence or position of a distant object such as a finger more than 5 cm away and the contact of this finger on the detection surface.

In the "floating" coupling capacity measurement mode of FIG. 2, the detection electronics is configured in the same manner as in FIG. 1, with a floating reference potential 9.

The electrodes of the lines 3 are emitting excitation electrodes, while the electrodes of the columns 4 are measuring measurement electrodes.

The function of the switches S9 and S10 is to connect the emitter electrode lines 3 to the ground M (which is also substantially the potential of a control object).

The active transmitter line 3 is selected by the switches S5 to

S8. Unused transmission lines 3 are set to reference potential 9 floating to limit parasitic capacitances.

The switches SU and S12 are also connected to the floating reference potential 9 in order to avoid capacitive leakage between the excitation signal and the receiving electrodes 4.

The switches S1 to S4 make it possible to select a receiving electrode 4 from the electrodes of the columns 4 and to connect it to the charge amplifier A, in order to measure the coupling capacity (possibly affected by the presence of the control object) between the emitting electrode 3 and the receiving electrode 4 selected. The reference potential 9 always remains at the same value as the potential of the receiver electrodes 4, which guarantees a good protection against parasitic capacitances.

In the coupling capacitance measurement mode of FIG. 3, the electronics are referenced to the ground M.

As before, the electrodes of the lines 3 are emitting, while the electrodes of the columns 4 are receivers.

Switches S9 and S10 function to connect the lines of electrodes 3 emitting, the excitation signal OSC. The active transmitter line 3 is selected by the switches S5 to S8.

The switches SU and S12 are connected to the reference or guard potential 9 in order to avoid capacitive leakage between the excitation signal and the 4 receiver columns.

The switch 13 ensures the excitation of the emitting electrodes 3. The external mass M is this time connected to the reference potential 9.

The switches S1 to S4 make it possible to select a receiving electrode 4 from the electrodes of the columns 4 and to connect it to the charge amplifier A, in order to measure the coupling capacity (possibly affected by the presence of the control object) between the emitting electrode 3 and the receiving electrode 4 selected.

The reference potential 9 always remains at the same value as the potential of the receiver electrodes 4, which guarantees a good protection against parasitic capacitances.

The AF floating power supply plays only a role of conventional power supply where electrical insulation at the excitation frequency is no longer necessary.

In all the detection modes, the output signal of the charge amplifier A is the image of the capacitance seen by the selected receiver electrode 3, 4. This signal is processed by the processing module Mod to determine the position and movement of the detected objects.

This information is sent in digital form to the external circuit which manages and processes the functions of the interface.

The device according to the invention can be implemented with a wide variety of electrode configurations. With reference to FIG. 4, the device according to the invention may comprise:

independent capacitive measuring electrodes 4 distributed over the entire detection surface 1 and connected to the charge amplifier A by scanners such as S1 to S4, but in a number equal to the number of electrodes;

one or a small number of capacitive electrodes (3) of excitation 3 are positioned so as to substantially surround the capacitive electrodes of measurement.

In the variants shown in FIGS. 4 (a) and 4 (b), there is only one capacitive excitation electrode 3 which forms a mesh around measurement electrodes 4. In the variant of FIG. Fig 4 (b), this electrode further extends along the edges of the detection surface 1.

In the variant shown in FIG. 4 (c), the capacitive excitation electrodes 3 are arranged in columns between the independent measurement electrodes 4.

The excitation electrodes 3 and measurement 4 can be separated by guard tracks. In order to be able to pass these tracks on the same surface, the mail constituting them the excitation electrode 3 are not closed on Fig ures 4 (a) and 4 (b).

The capacitive electrode (s) of excitation 3 may be made on the same surface as the measurement electrodes 4, or on another layer or a substantially parallel surface. They can in particular be made on a surface comprising the guard electrode 2.

The sensitive surface is thus substantially covered with multiplexed independent measuring electrodes 4, which can be used in the two direct capacitance measurement and coupling capacity measurement modes.

In the capacitance measurement mode, the excitation electrode (s) 3 are not used and are put to the potential of the guard 9 to which they contribute.

Coupling capacitance measurements are made between the excitation electrode (s) 3 and measurement electrodes 4, for example by measuring electrode measurement 4.

In the variant of FIG. 4 (c), all the excitation electrodes 3 can be interconnected to make only one of them, or S5 ... S8 scanners can be used to excite the electrodes. of excitement 3 located both measuring electrodes 4 being scanned, and setting the other excitation electrodes to the potential of the guard 9. According to other variants of embodiments:

- The electrodes 3, 4 may be placed in rows and columns or directions forming any angle between them;

The electrodes 3, 4 may comprise a succession of surfaces of all shapes;

- Any number of rows 3 and 4 columns of electrodes is possible as well as any distribution of the transmitter and receiver functions of the electrodes;

- The rows and columns of electrodes 3, 4 can be deposited on the same layer with electrical bridges 5, 6 to connect the surfaces without shorting the rows and columns.

Of course, the invention is not limited to the examples that have just been described and many adjustments can be made to these examples without departing from the scope of the invention.

Claims

A control interface device comprising:

a detection surface (1),

a plurality of capacitive electrodes (3, 4) arranged so as to substantially cover said detection surface (1),

capacitive electronic measurement means (8) capable of producing distance and / or contact information between at least one control object and capacitive electrodes (3, 4),

switching means (S9 to S13) capable of configuring said capacitive measurement electronic means (8) so as to allow direct measurements of capacitance between capacitive electrodes (3, 4) and one or more object (s) of control, and coupling capacitance variation measurements between capacitive excitation electrodes (3) and measuring electrodes (4), characterized in that said capacitive measuring electronic means

(8) are at least partially referenced to an electrical reference potential

(9) floating relative to a mass potential (M) during direct capacitance measurements.

2. Device according to claim 1, characterized in that the capacitive measuring means (8) are referenced to a reference electrical potential (9) fixed relative to the ground potential (M) during coupling capacity measurements.

3. Device according to claim 1, characterized in that the capacitive measuring means (8) are at least partly referenced to a reference electric potential (9) floating with respect to the ground potential (M) during capacitance measurements. coupling.

4. Device according to claim 3, characterized in that it further comprises switching means (S13) arranged in such a way as to connect at least one capacitive excitation electrode (3) to a fixed electrical potential. relative to the ground potential (M) when measuring coupling capacitances.

5. Device according to one of the preceding claims, characterized in that it further comprises switching means (S9 to S13) arranged so as to allow a change of reference electrical potential, between a floating potential and a potential. fixed with respect to the mass potential (M).

6. Device according to one of the preceding claims, characterized in that it further comprises a guard electrode (2) to an electrical reference potential (9) disposed near the capacitive electrodes (3, 4), according to their opposite side to the detection surface (1).

7. Device according to one of the preceding claims, characterized in that it further comprises scanning means (SI to S8) for:

- in direct capacitance measurements, select at least one measuring capacitive electrode (3, 4) so as to allow measurements of capacitance between this or these measurement electrode (s) (3, 4) and the control object (s),

- during the coupling capacitance measurements, selecting at least one capacitive excitation electrode (3) and at least one measuring capacitive electrode (4), so as to allow measurements of variation of coupling capacitance between said electrodes capacitive excitation (3) and measurement (4),

connecting the non-selected capacitive electrodes (3, 4) to the reference potential (9).

8. Device according to one of the preceding claims, characterized in that it comprises capacitive electrodes (3, 4) arranged substantially in two crossed directions.

9. Device according to claim 8, characterized in that it further comprises capacitive electrodes (3, 4) arranged in two superimposed layers, which layers comprising, respectively, electrodes in a first direction (3) and electrodes in a second direction (4).

10. Device according to one of claims 8 or 9, characterized in that it further comprises capacitive electrodes (3, 4) arranged in a layer, which electrodes comprising elements connected by bridge connections (5, 6). ) respectively, a first direction and a second direction.

11. Device according to one of claims 8 to 10, characterized in that it further comprises capacitive electrodes (3, 4) arranged in rows and columns.

12. Device according to one of claims 8 to 11, characterized in that it further comprises capacitive electrodes (3, 4) comprising a plurality of surfaces electrically connected to each other.

13. Device according to claim 12, characterized in that the surfaces are substantially of one of the following forms: square, rectangular, diamond-shaped, circular, elliptical.

14. Device according to one of claims 1 to 7, characterized in that it comprises:

independent capacitive measuring electrodes (4), distributed along the detection surface (1) and connected to scanning means,

a capacitive excitation electrode (3) arranged in such a way as to substantially surround the capacitive measuring electrodes.

15. Device according to one of the preceding claims, characterized in that it further comprises electrodes (3, 4) substantially transparent, based on ITO ("Indium Tin Oxide").

16. Control interface control method implementing a device according to one of the preceding claims, characterized in that it comprises steps of: configuration of the capacitive measurement electronic means (8) so as to allow direct measurements of capacitance,

- scanning of the measuring electrodes (3, 4) to detect supposed control objects,

if a plurality of control objects is detected, configuration of the capacitive measurement electronic means (8) so as to allow measurements of variation of coupling capacitors,

scanning of the capacitive excitation (3) and measurement (4) electrodes whose coupling regions are in or near areas of the measurement surface in which supposed control objects have been detected, to determine motions and / or control object contacts.