Device and method for detecting the approach and/or contact and pressure of an object in relation to a detection surface

Abstract

A detection device including: a measurement electrode, and a second electrode separated from one another by a distance (D) that is elastically modifiable locally, by a load exerted by an object on a detection surface, and a controller arranged in order to: connect the electrodes to an alternating guard potential (V.sub.g) in order to measure a capacitance representing an approach and a contact; and connect the second electrode to a second potential a second potential proportional to the guard potential (V.sub.g) and having a different amplitude, or to the ground potential (G), in order to measure a capacitance representing a pressure. Also provided is a detection method utilizing such a detection device.

Claims

1. A device for detecting an object with respect to a detection surface comprising: at least one electrode, called measurement electrode; at least one second electrode, placed facing said measurement electrode; said electrodes are separated by a distance (D) that is elastically modifiable locally, by a load exerted by said object on said detection surface; and at least one control means arranged in order to: apply to said electrodes: a same alternating potential (V.sub.g), called guard potential; that is different from a ground potential (G), so as to measure a first electrical signal with respect to a capacitance (C.sub.eo), called electrode-object capacitance, between said measurement electrode and said object; and apply to said second electrode: a second potential proportional to the guard potential (V.sub.g) and having a different amplitude, or the ground potential (G), so as to measure a second electrical signal with respect to the capacitance, called total capacitance, seen by said measurement electrode.

2. The device according to claim 1, characterized in that it comprises at least one calculation module configured to calculate a capacitance (C.sub.ie), called inter-electrode capacitance, between said measurement electrode and said second electrode, as a function of said total capacitance and said electrode-object capacitance (C.sub.eo).

3. The device according to claim 1, characterized in that it comprises a calculation module configured to at least one of: determine a distance or a contact between the object and the detection surface as a function of the first electrical signal; and determine a load, a force or a pressure applied by said object on the detection surface as a function of the second electrical signal.

4. The device according to claim 1, characterized in that the measurement electrode and the second electrode are separated by a layer that is elastically compressible comprising, or formed by, a dielectric material.

5. The device according to claim 1, characterized in that the measurement electrode is placed on, or in, or under, a support, produced from a flexible material, placed above and at a distance from the second electrode, and deforming at least locally when a load is exerted on said support.

6. The device according to claim 1, characterized in that it comprises several measurement electrodes.

7. The device according to claim 6, characterized in that it comprises one or more second electrodes arranged according to at least one of the following configurations: at least one second electrode placed opposite several, of the measurement electrodes; for at least one measurement electrode, a second electrode placed opposite said measurement electrode; for at least one measurement electrode, several second electrodes placed opposite said measurement electrode.

8. The device according to claim 1, characterized in that it comprises: an array of measurement electrodes, organized in rows and columns; and opposite each row, respectively each column, measurement electrodes, at least one row, respectively one column, constituted by one or more second electrode(s); the second electrode(s) of one and the same row, respectively one and the same column, being at the same potential.

9. A method for detecting an object with respect to a detection surface with a detection device according to claim 1, said method comprising at least one iteration of a first detection step, carried out by applying to the electrodes: a same alternating potential (V.sub.g), called guard potential; that is different to a ground potential (G), in order to determine a capacitance (C.sub.eo), called electrode-object capacitance, seen by the at least one measurement electrode as a function of a measured first signal; at least one iteration of a second detection step, comprising the following operations: applying to the at least one second electrode: a second potential proportional to the guard potential (V.sub.g) and having a different amplitude, or the ground potential (G); and determining a capacitance, called total capacitance, seen by the at least one measurement electrode as a function of a measured second signal.

10. The method according to claim 9, characterized in that the second detection step also comprises a step of calculating a capacitance (C.sub.ie), called inter-electrode capacitance, between said measurement electrode and said second electrode as a function of the total capacitance and of the electrode-object capacitance (C.sub.eo).

11. The method according to claim 9, characterized in that the second detection step is initiated when the electrode-object capacitance (C.sub.eo) reaches a predetermined threshold capacitance, or is within a predetermined range of threshold capacitances, representative of a contact between an object and the detection surface.

12. The method according to claim 11, characterized in that the detection device comprises a plurality of measurement electrodes equipping the detection surface, the second detection step being carried out only in an area of the detection surface in which the object was detected during the first detection step.

13. The method according to claim 11, characterized in that it comprises a step, called calibration step, comprising measuring and recording a threshold capacitance.

14. The method according to claim 13, characterized in that the calibration step comprises a determination of a threshold capacitance taking into account at least one of the following elements: a history measurement, a measurement environment.

15. The method according to claim 9, characterized in that it also comprises a step, called test step, carried out in the absence of the object, in order to verify the functioning of the device and comprising the following operations: applying the guard potential (V.sub.g) to the at least one measurement electrode; applying to the at least one second electrode a second potential between the guard potential (V.sub.g) and the ground potential (G), or the ground potential (G); determining a capacitance, called electrode-test capacitance, between said measurement electrode and second electrode by measuring a third signal; and comparing said electrode-test capacitance to a second predetermined threshold capacitance.

16. A detection layer, for an item of equipment, comprising a detection device according to claim 1.

17. An item of equipment equipped with a detection device according to claim 1.

18. A method for detecting an object with respect to a detection surface with a detection device according to claim 1, said method comprising at least one iteration of a first detection step, carried out by applying to the electrodes: a same alternating potential (V.sub.g), called guard potential; that is different to a ground potential (G), in order to determine a capacitance (C.sub.eo), called electrode-object capacitance, seen by the at least one measurement electrode as a function of a measured first signal; at least one iteration of a second detection step, comprising the following operations: applying to the at least one second electrode: a second potential proportional to the guard potential (V.sub.g) and having a different amplitude, or the ground potential (G); determining a capacitance, called total capacitance, seen by the at least one measurement electrode as a function of a measured second signal; and performing a test step, carried out in the absence of the object, in order to verify the functioning of the device and comprising the following operations: applying the guard potential (V.sub.g) to the at least one measurement electrode; applying to the at least one second electrode a second potential between the guard potential (V.sub.g) and the ground potential (G), or the ground potential (G); determining a capacitance, called electrode-test capacitance, between said measurement electrode and second electrode by measuring a third signal; and comparing said electrode-test capacitance to a second predetermined threshold capacitance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantages and characteristics will become apparent on examination of the detailed description of non-limitative examples and from the attached drawings in which:

(2) FIGS. 1a-1c are diagrammatic representations of the electrical principle of a first non-limitative embodiment example of a device according to the invention;

(3) FIG. 2 is a diagrammatic representation of the electrical principle of a second non-limitative embodiment example of a device according to the invention;

(4) FIG. 3 is a diagrammatic representation of the electrical principle of a third non-limitative embodiment example of a device according to the invention;

(5) FIG. 4 is a diagrammatic representation of the electrical principle of a fourth non-limitative embodiment example of a device according to the invention;

(6) FIGS. 5-8 are diagrammatic representations of different configurations of electrodes that can be implemented in a device according to the invention; and

(7) FIG. 9 is a diagrammatic representation, in the form of a flow chart, of a non-limitative embodiment example of a method according to the invention.

DETAILED DESCRIPTION

(8) It is well understood that the embodiments that will be described hereinafter are in no way limitative. In particular, variants of the invention may be envisaged comprising only a selection of characteristics described hereinafter, in isolation from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art. This selection comprises at least one,

(9) preferably functional, characteristic without structural details, or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art.

(10) In particular, all the variants and all the embodiments described may be combined together if there is no objection to such combination from a technical point of view.

(11) In the figures, elements that are common to several figures retain the same reference.

(12) FIGS. 1a-1c are diagrammatic representations of the electrical principle of a first non-limitative embodiment example of a detection device according to the invention.

(13) The device 100, represented diagrammatically in FIGS. 1a-1c, is intended to detect the approach, the contact and the pressure exerted by a control object 102 on a detection surface 104.

(14) The object 102 is on approach and at a distance from the detection surface 104 in FIG. 1a, in contact with the detection surface 104 in FIG. 1b and pressing on the detection surface in FIG. 1c.

(15) The device 100 represented in FIGS. 1a-1c comprises at least an electrode 106, called measurement electrode, placed according to a detection surface 104, and an electrode 108, called second electrode, placed facing the measurement electrode 106, below and at a distance from the measurement electrode 106.

(16) In the embodiments shown, the detection surface 104 is represented by a face of the measurement electrode or electrodes 106, preferably covered with a thin layer of electrically insulating material (polyimide, insulating varnish, etc.) in order to avoid short-circuits with the control object 102.

(17) The device 100 also comprises an electronic circuit which can be represented in the form of an operational amplifier (OA) 110, whose output is looped on its negative input by an impedance 112, which can be for example: a capacitor, a capacitor combined with a resistor, or

(18) a capacitor combined with a reset or discharge switch. In the example shown, the impedance 112 is formed by a capacitor C.

(19) A digital or analogue measurement module 114, connected to the output of the OA 110 makes it possible to measure and demodulate the voltage or the signal denoted V.sub.s, on the output of the OA 110.

(20) The device 100 also comprises an electrical source E, called guard electrical source, supplying an alternating potential, called guard potential, denoted V.sub.g, different from an electrical ground, denoted G.

(21) In the example shown in FIGS. 1a-1c: the measurement electrode 106 is connected to the negative input of the OA 110, and the electrical source E is connected to the positive input of the OA 110.

(22) Due to the very high impedance and open-loop gain of the OA 110, it can be considered that the measurement electrode 106 connected to the negative input of the OA 110 is polarized at the same potential as that present on the positive input of the OA 110.

(23) In the embodiments shown, the operational amplifier (OA) 110 is referenced to the guard potential V.sub.g. To this end, it is supplied by an electrical supply source (not shown) that is also referenced to the guard potential V.sub.g.

(24) Alternatively, the operational amplifier (OA) 110 can be referenced to the ground potential, while being supplied by an electrical supply source (not shown) referenced to the electrical ground potential G.

(25) It should be noted that the control object 102 is, by definition, normally polarized at the ground potential G directly or indirectly by resistive or capacitive coupling. Of course, it is not essential for the object to be perfectly polarized at this ground potential G. In order for it to be detectable, it must simply be polarized at a potential different from the guard potential V.sub.g.

(26) The voltage V.sub.s present on the output of the OA 110 is referenced to the guard potential V.sub.g.

(27) In order to obtain a voltage V.sub.s referenced to the general ground G, the processing module 114 can comprise in particular a differential amplifier electrically referenced to the general ground potential G. This differential amplifier is connected at the input respectively to the output of the OA 110 and to the guard potential and produces at the output an image signal of V.sub.s referenced to the general ground potential G.

(28) The device 100 also comprises a control module 116 controlling the operation of a controllable switch 118, placed between the second electrode 108 and the electrical source E. The controllable switch 118 is placed so that: in a first position, represented in FIGS. 1a and 1b, it connects the second electrode 108 to the guard potential V.sub.g; and in a second position, represented in FIG. 1c, it connects the second electrode 108 to the ground potential G.

(29) The controllable switch 118 is controlled in order to pass from the first position to the second position, in particular when the capacitance C.sub.eo, called electrode-object capacitance, formed between the measurement electrode 106 and the control object 102, reaches a predetermined threshold capacitance, denoted C.sub.s, predetermined and recorded in a recording means (not shown), for example in the control module 116. This threshold capacitance C.sub.s is predetermined and represents a contact between the control object 102 and the detection surface 104, as represented in FIG. 1b.

(30) The measurement electrode 106 is arranged such that the distance D between the measurement electrode 106 and the second electrode 108 can be elastically modified, locally, by a load exerted by the control object 102 on the detection surface 104. In particular, when a load is applied on the detection surface 104, the measurement electrode 106 moves closer to the second electrode 108, as shown in FIG. 1c. To this end, the measurement electrode 106 and the second electrode 108 are placed on either side of a layer 120 formed by an elastically compressible dielectric material, such as for example a foam or a silicone.

(31) Under these conditions, the approach and the contact of the control object 102 with the detection surface 104 are detected as a function of the value of the capacitance C.sub.eo formed between the measurement electrode 106 and the control object 102. When the capacitance C.sub.eo reaches a threshold capacitance C.sub.s, this indicates that the object 102 is in contact with the detection surface 104. In this case, the load exerted by the control object 102 is detected as a function of the capacitance C.sub.ie, called inter-electrode capacitance, formed between the measurement electrode 106 and the guard electrode 108.

(32) In order to determine the capacitance C.sub.eo, representative of the approach and the contact of the control object 102 with the detection surface 104, a first signal is measured periodically by setting the measurement electrode 106 and the second electrode 108 to the same alternating potential, i.e. to the guard potential V.sub.g supplied by the source E (FIG. 1a). In this configuration:

(33) $\begin{matrix} V_{s} = V_{g} \frac{C_{eo}}{C} & (1) \end{matrix}$

(34) This relationship (1) makes it possible to deduce the value of the electrode-object capacitance C.sub.eo from the measured first signal V.sub.s.

(35) It should be noted that in this configuration, the second electrode 108 acts as a guard electrode which prevents the appearance of parasitic coupling or leakage capacitances with the measurement electrode 106.

(36) While the control object 102 is at a distance from the detection surface 104, only the electrode-object capacitance C.sub.eo need be measured.

(37) When the control object 102 comes in contact with the detection surface 104, or in immediate proximity to this surface (semi-contact), it is necessary to also measure the inter-electrode capacitance C.sub.ie, representative of the pressure of the control object 102 on the detection surface 104. This inter-electrode capacitance C.sub.ie is determined in the following manner.

(38) The contact between the control object 102 and the detection surface 104 is determined when the capacitance C.sub.eo reaches a predetermined threshold value C.sub.s (or a range of threshold capacitances) (FIG. 1b). At that moment, the controllable switch 118 is toggled so as to connect the guard electrode 108 to the ground potential G, as shown in FIG. 1c. In this configuration, a second signal V.sub.s is measured at the output of the OA 110. This second signal V.sub.s is representative of a capacitance C.sub.T, called total capacitance, seen by the measurement electrode 106, so that:

(39) $\begin{matrix} V_{s} = V_{g} \frac{C_{T}}{C} & (2) \end{matrix}$

(40) This relationship (2) makes it possible to deduce the value of the total capacitance C.sub.T from the measured second signal V.sub.s.

(41) Yet, the total capacitance C.sub.T corresponds to the sum of: the electrode-object capacitance C.sub.eo, and the inter-electrode capacitance C.sub.ie which appears between the measurement electrode 106 and the second electrode 108 due to their potential difference.

(42) As the object 102 is in contact with the control surface 104, the electrode-object capacitance C.sub.eo no longer varies and is still equal to (or close to) the capacitance C.sub.s. Consequently, the value of the inter-electrode capacitance C.sub.ie, representative of the pressure of the object 102 on the detection surface 104, is obtained by subtraction, according to the following relationship:
C.sub.ie=C.sub.TC.sub.s(3)
or
C.sub.ie=C.sub.TC.sub.eoT(4)

(43) Where C.sub.eoT is the electrode-object capacitance measured with the object in contact.

(44) In this configuration, it is necessary to verify periodically if the control object 102 is still in contact with the detection surface 104. To this end, the controllable switch 118 is toggled periodically so as to connect the guard electrode 108 to the guard potential V.sub.g in order to measure the electrode-object capacitance C.sub.eo, then to the ground G in order to measure the total capacitance C.sub.T, and thus the inter-electrode capacitance C.sub.ie. These sequential measurements of C.sub.eo and C.sub.T are carried out as long as the electrode-object capacitance is higher than the threshold capacitance (C.sub.eoC.sub.s).

(45) By using for example the parallel-plate capacitor law, it is possible to link the electrode-object capacitance C.sub.eo and the inter-electrode capacitance C.sub.ie respectively to a distance between the measurement electrode and the object, and to a distance D between the measurement electrode and the second electrode. The load can thus be calculated from the variation in the measured thickness D of the dielectric material 120, and its modulus of elasticity.

(46) Determination of each of these capacitances from measured signals can be carried out by the measurement module 114, or by the control module, or even by one or more additional calculation module(s) (not shown).

(47) To this end, it is possible to utilize a synchronous demodulator which carries out multiplication functions of the signal V.sub.s originating from the OA 110 with a carrier signal corresponding to the guard potential V.sub.g, then low-pass filtering.

(48) It is also possible to use an asynchronous demodulator comprising a rectification followed by a low-pass filter.

(49) FIG. 2 is a simplified diagrammatic representation of the electrical principle of a second embodiment example of a device according to the invention.

(50) The device 200, shown in FIG. 2, comprises all the elements of the device 100 in FIGS. 1a-1c.

(51) Unlike the device 100, the device 200 does not comprise the controllable switch and comprises a second source E placed between the second electrode 108 and the ground potential G.

(52) The second source E is controlled by the control module 116 so that: the second source E supplies a potential V1 that is identical or substantially identical to the guard potential V.sub.g during measurement of the first signal: in this case the second electrode 108 is polarized (like the measurement electrode 106) at the guard potential V.sub.g; and the second source E supplies a second potential V1 proportional to, and of amplitude less than, the guard potential V.sub.g (V1=kV.sub.g where k<1) during measurement of the second signal: in this case the second electrode 108 is polarized at the potential V1 and the measurement electrode 106 is polarized at the guard potential V.sub.g.

(53) As above, the second source E is controlled in order to supply the guard potential V.sub.g as long as the capacitance C.sub.eo is less than the threshold capacitance C.sub.s, then when the capacitance C.sub.eo reaches the capacitance C.sub.s, it is controlled in order to supply the second potential V1=kV.sub.g and the guard potential V.sub.g alternately.

(54) In practice, the source E and the second source E are generated from one and the same oscillator or one and the same function generator in order to produce signals of identical shape, in phase, and which only differ in their amplitude.

(55) The use of a second potential has the advantage of allowing an adjustment of the gain of the detection in order to be able to detect the electrode-object capacitance C.sub.eo and the total capacitance C.sub.T under optimal conditions. Indeed, due to the relationship between the opposing surfaces, the inter-electrode capacity C.sub.ie and thus the total capacity C.sub.T can be several orders of magnitude greater than the electrode-object capacitance C.sub.eo.

(56) Using the second potential V1=kV.sub.g, the signals measured as indicated above become respectively:

(57) $\begin{matrix} V_{s} = V_{g} \frac{C_{eo}}{C} and & (5) \\ V_{s} = \frac{V_{g}}{C} (C_{eo} + (1 - k) C_{eg}) = \frac{V_{g}}{C} (C_{T} - k C_{eg}) & (6) \end{matrix}$

(58) It is thus possible to optimize the detection gain in order to detect the electrode-object capacitance C.sub.eo corresponding to distant objects, and to detect the total capacitances C.sub.T without saturation due to the attenuation of a factor (1k) obtained.

(59) Alternatively, the second source E can be controlled by the control module 116 so as to either supply the guard potential V.sub.g, or to be turned off so that the second electrode is polarized at the ground potential G. In this case, in the device 200 in FIG. 2, it is also possible to add a controllable switch between the guard electrode 106 and the second source E, in order to avoid turning off and turning on the second source E, such a controllable switch connecting the second electrode 108: to the second source E in order to measure the first signal; and to the ground potential G in order to measure the second signal.

(60) Of course, in all the embodiments presented, the measurement of the total capacitance C.sub.T can be carried out according to other criteria than a detection of the condition in which the electrode-object capacitance C.sub.eo reaches the threshold capacitance C.sub.s.

(61) In particular, it is possible to periodically and sequentially measure the electrode-object capacitance C.sub.eo and the total capacitance C.sub.T as described above, in the same manner and without taking into account the fact of whether or not the control object 102 is in contact with the detection surface 104.

(62) It is also possible to periodically carry out a verification of the satisfactory operation of the system. To this end: in the absence of objects 102 (or at least when the measured values of the electrode-object capacitance C.sub.eo are sufficiently low as to correspond to an absence of objects), a measurement of the total capacitance C.sub.T is carried out, which under these conditions must correspond to a measurement of the inter-electrode capacitance C.sub.ie; the value of the inter-electrode capacitance C.sub.ie obtained is compared to an expected inter-electrode capacitance value or range of values, and if the difference does not satisfy a pre-established criterion, the system can be considered to be faulty and an alarm triggered.

(63) It is also possible to calibrate the inter-electrode capacitance measurements in order, for example, to take into account the ageing or irreversible deformations of the dielectric material 120, and thus produce more precise load or force measurements. To this end: in the absence of objects 102 in contact with the detection surface 104 (or at least when the measured values of electrode-object capacitance C.sub.eo are sufficiently low as to correspond to an object at a distance from the detection surface or an absence of objects), a measurement of the total capacitance C.sub.T is carried out, which under these conditions must correspond to a measurement of the inter-electrode capacitance C.sub.ie; This measurement of the inter-electrode capacitance C.sub.ie is used as reference value that is a no-load value, or without depression, and/or a nominal thickness of dielectric 120 (i.e. without applied stress) is deduced therefrom.

(64) FIG. 3 is a simplified diagrammatic representation of the electrical principle of a third embodiment example of a device according to the invention.

(65) The device 300, shown in FIG. 3, comprises all the elements of the device 100 in FIGS. 1a-1c.

(66) Unlike the device 100, the device 300 comprises, in addition to the measurement electrode 106 and the second electrode 108, additional guard electrodes 302.

(67) These additional guard electrodes 302 are polarized at the guard potential V.sub.g, like the measurement electrodes 106, and thus serve as active guard electrodes in order to remove the parasitic or leakage coupling capacitances with the environment. To this end, they can be connected to the positive input of the OA 110, as shown. In particular, the additional guard electrodes 302 can be produced in the form of an additional openwork guard plane with the second electrodes 108 placed in the openings of this additional guard plane 302.

(68) Thus, in order to measure the first signal, all the electrodes 106, 108 and 302 are polarized at the guard potential V.sub.g. For the measurement of the second signal, the measurement electrode 106 and the additional guard electrode 302 are kept at the guard potential V.sub.g, and the second electrode 108 is set at the ground potential G, by the switch 118 controlled by the control module 116.

(69) The device 300 is also arranged in order to make it possible to manage a plurality of measurement electrodes 106 sequentially with one and the same electronic detection unit (and in particular one and the same OA 110). To this end, it comprises an electrode switch 304 which makes it possible to selectively connect the measurement electrodes 106 either to the negative input of the OA 110 in order to carry out measurements (active measurement electrode 106) or to the guard potential V.sub.g for example at the positive input of the OA 110. The electrode switch 304 is also arranged so that when a measurement electrode 106 is connected to the input of the OA 110, thus active, the other measurement electrodes 106 are polarized at the guard potential V.sub.g and contribute to the guard elements.

(70) In a configuration with a plurality of measurement electrodes 106, the switch 118 which controls the potential of the second electrode can be configured in different ways.

(71) In order to measure the first signal, all the second electrodes 108 are polarized at the guard potential V.sub.g.

(72) In order to measure the second signal, the switch 118 can be configured so as to: either connect all the second electrodes 108 to the ground potential G; or connect the second electrode 108 opposite the active measurement electrode 106 (connected to the negative input of the OA 110) to the ground potential G and connect all the other second electrodes 108 to the guard potential V.sub.g so that they contribute to the guard elements.

(73) Of course, alternative embodiment examples may be obtained by combining the embodiment example in FIG. 3 with that in FIG. 2, i.e. using a second source E in order to polarize the second electrodes 108 at a second potential for the measurement of the second signal, as described above.

(74) FIG. 4 is a simplified diagrammatic representation of the electrical principle of such an alternative embodiment example.

(75) In order to manage a plurality of electrodes 106, it is possible to utilize an electrode switch 304 as described above.

(76) It is also possible to utilize a switch 118 in order to switch the potential of the second electrode or electrodes 108, either to the guard potential V.sub.g, or to the second potential as generated by the second source E.

(77) As above, in order to measure the second signal, the switch 118 can thus be configured so as to: either connect all the second electrodes 108 to the second potential of the second source E; or connect the second electrode 108 facing the active measurement electrode 106 (connected to the negative input of the OA 110) to the second potential and connect all the other second electrodes 108 to the guard potential V.sub.g so that they contribute to the guard elements.

(78) FIG. 5 is a diagrammatic representation of a first configuration of electrodes which can be utilized in a device according to the invention.

(79) In the configuration 500, represented in FIG. 5, the device can comprise a plurality of measurement electrodes 106.sub.1-106.sub.N, and a second single electrode 108 common to all the measurement electrodes 106.sub.1-106.sub.N.

(80) FIG. 6 is a diagrammatic representation of a second configuration of electrodes which can be utilized in a device according to the invention.

(81) In the configuration 600, represented in FIG. 8, the device can comprise a plurality of measurement electrodes 106.sub.1-106.sub.N and a second individual electrode, respectively 108.sub.1-108.sub.N, for each measurement electrode 106.sub.1-106.sub.N.

(82) FIG. 7 is a diagrammatic representation of a third configuration of electrodes which can be utilized in a device according to the invention.

(83) In the configuration 700, represented in FIG. 7, the device can comprise a plurality of measurement electrodes 106.sub.1-106.sub.N and for each measurement electrode 106.sub.1-106.sub.N: a second individual electrode, respectively 108.sub.1-108.sub.N; and an individual openwork additional guard electrode, respectively 302.sub.1-302.sub.N.

(84) FIG. 8 is a diagrammatic representation of a fourth configuration of electrodes which can be utilized in a device according to the invention.

(85) In the configuration 800, represented in FIG. 8, the device can comprise a plurality of measurement electrodes 106.sub.1-106.sub.N.

(86) The device also comprises one single additional guard electrode 302, common to the set of measurement electrodes 106.sub.1-106.sub.N, and forming a guard plane.

(87) The device comprises for each measurement electrode 106.sub.1-106.sub.N, a second individual electrode, respectively 108.sub.1-108.sub.N, inserted into the guard plane formed by the single additional guard electrode 302.

(88) FIG. 9 is a diagrammatic representation, in the form of a flow chart, of a non-limitative embodiment of a detection method according to the invention.

(89) The method 900 comprises one or more iteration(s) of a first detection step 902, carried out when a control object approaches the detection surface.

(90) This first detection step 902 comprises step 904 of setting the measurement electrode and the second electrode, which can be a guard electrode or a test electrode, to the guard potential as described above.

(91) Thus, a step 906 measures a first signal representative of the electrode-object capacitance C.sub.eo.

(92) As a function of the measured signal, the capacitance C.sub.eo is calculated during a step 908.

(93) During a step 910, the measured capacitance C.sub.eo is compared to a predetermined threshold capacitance C.sub.s representing an electrode-object capacitance obtained when there is contact between the control object and the detection surface.

(94) If the capacitance C.sub.eo<C.sub.s, then step 904 is reiterated, for example at a predetermined frequency.

(95) If the capacitance C.sub.eoC.sub.s then step 904 is followed by a second detection step 912.

(96) This second detection step 912 comprises step 914 of setting the second electrode to the ground potential or to the second potential. The measurement electrode is kept at the guard potential.

(97) Then, step 916 performs a measurement of a second signal representative of the total capacitance C.sub.T seen by the measurement electrode.

(98) As a function of the measured second signal, the capacitance C.sub.T is calculated during step 918.

(99) Then, step 919 measures a first signal representative of the electrode-object capacitance C.sub.eo.

(100) As a function of the measured signal, the capacitance C.sub.eo is calculated during step 920.

(101) During step 921, the inter-electrode capacitance C.sub.ie, representative of the pressure of the control object on the detection surface, is calculated by subtracting the threshold capacitance C.sub.s from the calculated capacitance C.sub.T.

(102) While the capacitance C.sub.eoC.sub.s then step 912 is reiterated. Else, the method 900 resumes at step 902.

(103) It should be noted that the steps of measuring the capacitance C.sub.eo in order to determine the inter-electrode capacitance C.sub.ie may not be performed at all the iterations of the second detection step 912, but more infrequently, and the capacitance C.sub.eo recorded.

(104) Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without exceeding the scope of the invention.

Device and method for detecting the approach and/or contact and pressure of an object in relation to a detection surface

Assignee

Inventors

Cpc classification

Classification Explorer

H03K2017/9606

ELECTRICITY

Classification Explorer

H03K17/955

ELECTRICITY

Classification Explorer

G01L1/14

PHYSICS

Classification Explorer

H03K17/975

ELECTRICITY

Classification Explorer

H03K2217/960765

ELECTRICITY

Classification Explorer

B25J13/087

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

H03K17/962

ELECTRICITY

Classification Explorer

H03K2017/9615

ELECTRICITY

International classification

Classification Explorer

G01L1/14

PHYSICS

Classification Explorer

B25J13/08

PERFORMING OPERATIONS; TRANSPORTING

Abstract

Claims

Description