Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
  • G06F3/0443—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means using a single layer of sensing electrodes
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/0416—Control or interface arrangements specially adapted for digitisers
  • G06F3/0418—Control or interface arrangements specially adapted for digitisers for error correction or compensation, e.g. based on parallax, calibration or alignment
  • G06F3/04182—Filtering of noise external to the device and not generated by digitiser components
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F2203/00—Indexing scheme relating to G06F3/00 - G06F3/048
  • G06F2203/041—Indexing scheme relating to G06F3/041 - G06F3/045
  • G06F2203/04101—2.5D-digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F2203/00—Indexing scheme relating to G06F3/00 - G06F3/048
  • G06F2203/041—Indexing scheme relating to G06F3/041 - G06F3/045
  • G06F2203/04107—Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/0416—Control or interface arrangements specially adapted for digitisers
  • G06F3/04164—Connections between sensors and controllers, e.g. routing lines between electrodes and connection pads

Definitions

• the present invention relates to a capacitive control interface device adapted to the implementation of measurement electrodes with highly resistive connection tracks. It also relates to an apparatus with a control interface comprising such a device, and a method implemented in this device or this apparatus.
• the field of the invention is more particularly but not limited to that of touch and / or gesture control interfaces, in particular for smartphones, tablets or touch screens.
• Touch and / or gesture control interfaces that is to say, able to determine the presence of control objects in their contactless neighborhood
• smartphones, tablets and touch screens are frequently used in particular in smartphones, tablets and touch screens. They are then transparent and superimposed on the display screen.
• 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 objects to be detected (such as fingers) in order to carry out a command.
• Capacitive techniques commonly 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.
• the electrodes can also be in the form of lines and columns as the techniques of the "mutual capacitance" type.
• matrix electrode structures with individual electrodes, often of rectangular shape, distributed over the entire tactile surface.
• FR2949007 from Rozière discloses a capacitive proximity sensor comprising a plurality of independent electrodes, which makes it possible to measure the capacitance and the distance between the electrodes and one or more objects in the vicinity.
• the implemented technology uses a guard to eliminate any stray capacitance. All the electrodes are at the same potential and there is thus no coupling capacity between the electrodes likely to degrade the measurement of the capacitance.
• This technology is well suited to the realization of capacitive control interfaces in the form of pads or small transparent tactile and gestural (3D) panels, such as laptop touchpad or screens for smartphones.
• the measurement of the ability to detect is generally performed with a voltage capacitance converter using charge transfer circuits with capacitive switching or charge amplifiers.
• the analog measurement signal thus obtained which is at the frequency of the excitation signal, is then demodulated and digitally processed.
• the demodulation and digital processing solutions used in these systems generally require processing a large number of periods the analog measurement signal to obtain a measure of usable capacity. In practice, at least ten periods of the excitation signal are used to obtain a capacity measurement.
• an excitation frequency of at least 100 KHz is required.
• Another advantage of using a frequency of the order of 100 KHz is that it makes it possible to work in a frequency window relatively remote from the most common electromagnetic disturbances, including in particular the 50-60 Hz of the sector and the frequencies of the order of magnitude. 1 M Hz and beyond digital and radio circuits.
• the excitation frequencies commonly used are between 50 KHz and 500 KHz.
• a constraint of transparent matrix electrode structures is that they require the presence on the touch surface of connecting tracks that connect each individual electrode to the electronics. Indeed, the technologies used to make transparent capacitive slabs do not allow the use of multilayer solutions with metallized holes as for printed circuits, where the connecting tracks can be buried under the electrodes.
• the connecting tracks and the transparent electrodes are generally made with ⁇ (indium-tin oxide).
• This material is relatively resistive (100 to 200 ohm / square), and it is necessary to make wide tracks to limit the total electrical resistance of these tracks. This constraint is well known to manufacturers of transparent touch panels. It is easily compatible with electrode solutions in the form of lines and columns. Indeed, these lines and these columns are generally a width of several millimeters, which allows to obtain a total resistance less than about 10 kohm for slabs up to 10 inches (250 mm) diagonally.
• An object of the present invention is to provide a capacitive control interface device and method which is less sensitive than the devices and methods of the prior art to the resistivity of elements such as electrodes, link tracks and the guard elements, and which is able to perform precise measurements even with highly resistive elements.
• Another object of the present invention is to provide a device and a method of capacitive control interface that allow the implementation of matrix structures of transparent electrodes on large panels.
• Another object of the present invention is to provide a device and a capacitive control interface method that allow the implementation of matrix structures of transparent electrodes with connection tracks on the same layer as the transparent electrodes, and arranged so that the detection of control objects is not disturbed by the presence of these link tracks.
• an interface device for controlling actions of at least one object of interest that is capacitively detectable in a measurement zone comprising:
• a detection surface provided with a plurality of capacitive measuring electrodes
• excitation means capable of biasing said measuring electrodes to an alternating electric excitation potential
• measuring means able to measure a capacitive coupling between said measurement electrodes and at least one object of interest
• guard elements made of electrically conductive material disposed in proximity to said measuring electrodes at least in their opposite face to the measurement zone and biased to an alternating electrical reserve potential substantially identical to said electric excitation potential
• the excitation means are arranged so as to generate an electric excitation potential with a sufficiently low excitation frequency for measuring electrodes capacitively coupled to at least one object of interest and their tracking track. link have an electrical impedance at said excitation frequency whose resistive portion is much lower than the module of the reactive part.
• This equivalent capacitance C T represents the capacitive couplings between the electrode and its connecting track, and, on the one hand, the object of interest (capacitance of interest C x ), and on the other hand, the environment and the guard (parasitic capacitance C P) .
• j is the imaginary unit. It should be noted that the parasitic capacitance C P due to the coupling of the measuring electrode with the guard elements located in the vicinity is necessarily of a relatively large value, and therefore not negligible.
• the excitation frequency f is chosen such that the resistive portion R of the complex impedance Z is much smaller than the 1 / coC T module of the reactive part.
• the resistive part R does not introduce significant measurement error, in the context of the measurement, when it is not taken into account in the calculation of the equivalent capacitance C T from the impedance Z complex;
• the resistive portion R is negligible, in the context of the measurement, with respect to the l / coC T module of the reactive part;
• the resistive portion R is less than 1/2, respectively 1/5 or 1/10 of the value of the l / coC T module of the reactive part.
• a predetermined control object such as a finger or a stylet
• a predetermined measurement zone for example between 0 and 10 cm from the electrode, or 0 and 5 cm from the electrode, or 0 and 2 cm from the electrode
• the excitation frequency can be chosen so as to be:
• the excitation frequency may in particular be less than or equal to at least one of the following values: 20 Khz, 4 Khz.
• the device according to the invention can comprise:
• switching means capable of selectively connecting the measuring electrodes to the measuring means
• connection means disposed at the periphery of said detection surface
• connection tracks whose part on the detection surface has a width that is sufficiently narrow so that the surface of said connection tracks on said detection surface is negligible in front of the surface of the measurement electrodes;
• the device according to the invention may comprise measuring electrodes distributed in a row and column arrangement. These electrodes can be made in two superimposed layers of material, or consist of patches made in a layer of material and interconnected by bridge connections so as to form lines and columns.
• the device according to the invention allows the realization of panels or measuring surfaces, in particular transparent, in a simple and inexpensive way, and which allow precise measurements. Indeed :
• the electrodes and the connecting tracks can be deposited on the same surface in a single layer of conductive material (for example ITO), which makes it possible to minimize the production costs;
• the connection tracks can be made with a width that is sufficiently narrow so that they do not influence the detection of an object of interest significantly.
• This influence is geometric in nature: it depends on the width of the connecting track on the detection surface, which determines the surface of the track and therefore the coupling capacity that can appear between an object of interest and this connection track .
• this capacitive coupling is assigned to the electrode to which the track is connected, it introduces an error in the location in the plane of the control surface of the object of interest. And therefore this geometric error can be minimized with the device according to the invention;
• the device according to the invention is able to perform accurate capacity measurements including under these conditions.
• the track width on the measurement surface can be chosen such that the location errors due to the capacitive couplings between the object of interest and the connection tracks are negligible or at least acceptable;
• the excitation frequency f can then be chosen as explained above as a function of the value of the resistive portion R which is determined by the selected track widths and their resistivity.
• the device according to the invention may comprise measurement means at least partly referenced to the electrical excitation potential.
• a method for controlling actions of at least one object of interest that is capacitively detectable in a measurement zone implementing:
• a detection surface provided with a plurality of capacitive measuring electrodes
• guard elements made of electrically conductive material disposed in proximity to said measuring electrodes at least along their face opposite to the measurement zone, and electrical connection tracks arranged at least in part on said detection surface between measuring electrodes and arranged in such a way as to connect said measurement electrodes to said electronic and processing means,
• method further comprises a step of generating an electric excitation potential with a sufficiently low excitation frequency so that measuring electrodes capacitively coupled to at least one object of interest and their connecting track have an electrical impedance at said excitation frequency whose resistive portion is much smaller than the modulus of the reactive part.
• Capacitive coupling measurement can include steps:
• an apparatus comprising an interface device according to the invention.
• This apparatus may comprise a display screen and a detection surface provided with a plurality of transparent capacitive measuring electrodes superimposed on said display screen.
• this device can be of one of the following types: smartphone, tablet, touch screen.
• FIG. 1 illustrates a transverse view of a measurement interface implemented in an interface device according to the invention
• FIG. 2 illustrates a front view of a measurement interface implemented in an interface device according to the invention
• FIG. 3 shows a block diagram of a capacitive detection electronics implemented in an interface device according to the invention
• FIG. 4 shows an electronic diagram equivalent to that of FIG. 3 which takes into account the resistivity of the connecting tracks and the resulting leakage capacities
• FIG. 5 shows an electronic diagram equivalent to that of FIG. 3 which takes into account the resistivity of the connecting tracks and the guard elements, and the resulting leakage capacities.
• Such a control interface is particularly suitable for producing tactile and contactless control interfaces, or human-machine interfaces, for systems or devices such as mobile phones (smartphones), tablets, computers or computers. control slabs.
• control interface 2 comprises a detection surface 4 provided with capacitive measuring electrodes 5.
• These measurement electrodes 5 are distributed for example in a matrix arrangement on the detection surface 4, as shown in FIG. 2.
• the measuring electrodes 5 are made of a substantially transparent conductive material, such as, for example, ⁇ (indium tin oxide) deposited on a dielectric material (glass or polymer). They can be superimposed on a display screen, for example TFT (thin film transistor) or OLED (organic light-emitting diodes) type.
• ⁇ indium tin oxide
• dielectric material glass or polymer
• TFT thin film transistor
• OLED organic light-emitting diodes
• the measurement electrodes 5 can detect the presence and / or the distance of at least one object of interest 1, which is also a control object 1, in a measurement zone.
• the measurement electrodes 5 and their associated electronics are configured so as to allow the simultaneous detection of several objects 1.
• the position of the object 1 or objects 1 in the plane of the detection surface 4 is determined from the position (on this detection surface 4) of the measurement electrodes 5 which detect the objects 1.
• the distance 3, or at least one piece of information representative of the distance 3, between the objects 1 and the detection surface is determined from measurements of the capacitive coupling between the electrodes 5 and the objects 1.
• One or more guard electrodes 6 are positioned according to the rear face of the measurement electrodes 5, relative to the detection zone of the objects 1. They are also made of a substantially transparent conductive material, such as, for example, ⁇ (oxide of indium-tin), and are separated from the measuring electrodes 5 by a layer of dielectric material.
• ⁇ oxide of indium-tin
• the measuring electrodes 5 are connected to capacitive measurement electronic means 17.
• connection is made in particular by substantially transparent connection tracks 7 which are arranged on the detection surface 4 between the electrodes 5.
• These connecting tracks 7 are made of the same material as the electrodes 5, for example ⁇ (indium tin oxide).
• the connecting tracks 7 and the electrodes 5 can be deposited simultaneously, in one or the same layers.
• connection means 8 located at the periphery of the detection zone 4, outside the transparent useful zone. These connection means 8 are in turn connected to the capacitive measurement electronic means 17.
• the capacitive measurement electronic means 17, in the embodiment of FIG. 3, are in the form of a floating bridge capacitive measuring system as described for example in the document FR 2 949 007 Rozière.
• the detection circuit comprises a so-called floating portion 16 whose reference potential 11, called guarding potential 11, oscillates with respect to the ground 13 of the overall system, or to the ground.
• the potential difference between the guard potential 11 and the ground 13 is generated by an excitation source, or an oscillator 14.
• the guard electrodes 6 are connected to the guard potential 11.
• the floating part 16 comprises the sensitive part of the capacitive detection, in particular a charge amplifier. It can of course include other means of processing and conditioning the signal, including digital or microprocessor-based, also referenced to the potential of guard 11.
• floating supply transfer means 15 comprising, for example, DC / DC converters.
• This capacitive measuring system makes it possible to measure capacitance information between at least one measuring electrode 5 and a control object 1.
• the control object 1 must be connected to a potential d ifferent of the guarding potential 11, such as, for example, the ground potential 13. This is the case when the control object 1 is a finger of a user whose body defines a mass, or an object (such as a stylus) manipulated by that user.
• the device according to the invention may furthermore include analog switches or switches 10, controlled by electronic control means. These switches 10 make it possible to selectively select measurement electrodes 5 and connect them to the capacitive detection electronics 17 to measure the coupling capacitance with the object 1.
• the switches 10 are configured in such a way that a measuring electrode 5 is connected either to the capacitive detection electronics 17 or to the guard potential 11.
• the switches 10 thus make it possible to selectively interrogate all the measurement electrodes 5 to obtain an image of capacitive coupling between one or more control objects 1 and the measurement electrodes 5.
• the capacitive detection electronics 17 may comprise as many parallel detection channels, each with its charge amplifier, as there are measuring electrodes 5 to be interrogated.
• the device does not necessarily include switches 10;
• the capacitive detection electronics 17 may comprise a plurality of detection channels in parallel with each of its charge amplifiers, and the switches may be configured in such a way that each channel of detection can sequentially interrogate a plurality of measuring electrodes 5;
• the capacitive detection electronics 17 may comprise only one detection channel, and switches 10 configured so as to be able to interrogate sequentially all the measurement electrodes 5. This is the configuration illustrated in FIG. 3;
• the sensitive part of the detection is protected by a guard shield 12 connected to the guard potential 11.
• the floating electronics 16 is connected at the output to the electronics of the system 18 referenced to ground by electrical connections compatible with the difference of reference potentials.
• These links may comprise, for example, differential amplifiers or optocouplers.
• the charge amplifier 16 as implemented in the diagram of FIG. 3 makes it possible to convert the capacitance C x created between an electrode 5 and the control object 1 into voltage.
• V s V (Cx / C B ). (Eq. 1)
• V s V (C x / C B ) (1 / (1 + j R (C x + C P ) co)).
• the resistance R of the connecting tracks 7 is therefore troublesome according to several aspects:
• connection tracks 7 between the measurement electrodes 5 does not interfere with the detection and location of the object of interest 1, it is necessary to reduce their width, for example to less than 100 pm.
• the resistances of these connection tracks 7 can then easily exceed 100 KOhm when they are made of ITO.
• this condition can be satisfied by choosing an excitation frequency f such that:
• the measurement signal V s is a signal modulated at the excitation frequency f, and it is its modulation amplitude at this excitation frequency f which is representative of the capacitance measurement.
• the measurement signal V s can be demodulated by a synchronous demodulator at the electronics of the system 18 referenced to ground. This procedure, however, has the disadvantage of requiring a large number of periods of the excitation signal to obtain a measurement value.
• the device according to the invention comprises sampling and digitizing means which make it possible to directly digitize the measurement signal V s , for example at the electronics of the system 18 referenced to ground. This digitization is all the easier as the excitation frequency f is low. The amplitude of modulation at the excitation frequency f is then directly deduced from an analysis of the temporal shape of one or a few periods of this measurement signal V s .
• a panel comprising a few hundred measuring electrodes 5 can be "read” several times per second, even with an excitation frequency of less than 10 KHz.
• Fig. 5 shows an equivalent diagram of the complete structure of a control interface 2 in the form of a transparent panel 2 superimposed on a display screen.
• the guard plane 6, in ITO, has a much lower electrical resistance r than that of the connecting tracks 7 but which is nevertheless significant. Indeed, this electrical resistance r can be of the order of a few tens to a few hundred ohm depending on the nature of ⁇ deposited and the size of the screen.
• This phenomenon can generate a capacitive offset of several tens of femtofarads.
• the invention and in particular the implementation of a low excitation frequency also makes it possible to make this capacitive leak negligible.

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• 2013
  • 2013-05-17 FR FR1354472A patent/FR3005763B1/fr not_active Expired - Fee Related
• 2014
  • 2014-04-09 EP EP14721224.5A patent/EP2997455A1/fr not_active Ceased
  • 2014-04-09 US US14/891,958 patent/US9983746B2/en active Active
  • 2014-04-09 WO PCT/EP2014/057161 patent/WO2014183932A1/fr active Application Filing
  • 2014-04-09 CN CN201480040202.7A patent/CN105531656B/zh not_active Expired - Fee Related

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