WO2012050875A1 - Capteur tactile hybride capacitif à détection de force - Google Patents

Capteur tactile hybride capacitif à détection de force Download PDF

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Publication number
WO2012050875A1
WO2012050875A1 PCT/US2011/053638 US2011053638W WO2012050875A1 WO 2012050875 A1 WO2012050875 A1 WO 2012050875A1 US 2011053638 W US2011053638 W US 2011053638W WO 2012050875 A1 WO2012050875 A1 WO 2012050875A1
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WIPO (PCT)
Prior art keywords
capacitance
force
touch
magnitude
location
Prior art date
Application number
PCT/US2011/053638
Other languages
English (en)
Inventor
Massoud Badaye
Greg Landry
Original Assignee
Cypress Semiconductor Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US13/091,132 external-priority patent/US9459736B2/en
Application filed by Cypress Semiconductor Corporation filed Critical Cypress Semiconductor Corporation
Publication of WO2012050875A1 publication Critical patent/WO2012050875A1/fr

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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
    • G06F3/0445—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
    • 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
    • G06F2203/00—Indexing scheme relating to G06F3/00 - G06F3/048
    • G06F2203/041—Indexing scheme relating to G06F3/041 - G06F3/045
    • G06F2203/04105—Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position

Definitions

  • This disclosure relates to the field of capacitive sensors and, in particular, to a method of measuring force using a capacitive sensor array.
  • Computing devices such as notebook computers, personal data assistants (PDAs), kiosks, and mobile handsets, have user interface devices, which are also known as human interface devices (HID).
  • user interface devices which are also known as human interface devices (HID).
  • One user interface device that has become more common is a touch-sensor pad (also commonly referred to as a touchpad).
  • a basic notebook computer touch-sensor pad emulates the function of a personal computer (PC) mouse.
  • a touch-sensor pad is typically embedded into a PC notebook for built-in portability.
  • a touch-sensor pad replicates mouse X/Y movement by using two defined axes which contain a collection of sensor elements that detect the position of one or more conductive objects, such as a finger.
  • Mouse right/left button clicks can be replicated by two mechanical buttons, located in the vicinity of the touchpad, or by tapping commands on the touch-sensor pad itself.
  • the touch-sensor pad provides a user interface device for performing such functions as positioning a pointer, or selecting an item on a display.
  • These touch-sensor pads may include multidimensional sensor arrays for detecting movement in multiple axes.
  • the sensor array may include a one-dimensional sensor array, detecting movement in one axis.
  • the sensor array may also be two dimensional, detecting movements in two axes.
  • Touch screens also known as touchscreens, touch windows, touch panels, or touchscreen panels
  • transparent display overlays which are typically either pressure-sensitive (resistive or piezoelectric), electrically-sensitive (capacitive), acoustically-sensitive (surface acoustic wave (SAW)) or photosensitive (infra-red).
  • SAW surface acoustic wave
  • the effect of such overlays allows a display to be used as an input device, removing the keyboard and/or the mouse as the primary input device for interacting with the display's content.
  • Such displays can be attached to computers or, as terminals, to networks.
  • Touch screens have become familiar in retail settings, on point-of-sale systems, on ATMs, on mobile handsets, on kiosks, on game consoles, and on PDAs where a stylus is sometimes used to manipulate the graphical user interface (GUI) and to enter data.
  • GUI graphical user interface
  • a user can touch a touch screen or a touch-sensor pad to manipulate data. For example, a user can apply a single touch, by using a finger to touch the surface of a touch screen, to select an item from a menu.
  • Figure 1 is a block diagram illustrating an embodiment of an electronic system that processes touch sensor data.
  • Figure 2 is a block diagram illustrating an embodiment of an electronic system that processes touch sensor data.
  • Figure 3A illustrates a profile view of a flexible touch-sensing surface, according to an embodiment.
  • Figure 3B illustrates a profile view of a dual layer flexible touch- sensing surface, according to an embodiment.
  • Figure 4A illustrates an embodiment of a capacitive sensor array.
  • Figure 4B illustrates a capacitance profile of a capacitive sensor array, according to an embodiment.
  • Figure 5 illustrates a three-dimensional (3D) lookup table, according to an embodiment.
  • Figure 6 illustrates a layer of a 3D lookup table, according to an embodiment.
  • Figure 7 is a graph illustrating interpolation between layers of a 3D correction table, according to an embodiment.
  • Figure 8 is a graph illustrating extrapolation based on layers of a 3D correction table, according to an embodiment.
  • Figure 9 is a flow diagram illustrating an embodiment of a force detection process.
  • a flexible touch-sensing surface comprising a capacitive sensor array may be used to determine a magnitude of force applied by a finger or other object to the touch-sensing surface, based on capacitance measurements of the sensor array. Such a touch-sensing surface may further be used to determine an amount of deflection of the sensor at or near a point where the force is applied.
  • a flexible touch-sensing surface may include a capacitive sensor array with a highly flexible overlay made of a material such as Poly(methyl methacrylate), or PMMA.
  • the capacitive sensor array may respond to changes in capacitance resulting from proximity of a conductive object to the capacitive sensor array, or to pressure applied by a conductive or nonconductive object to the surface of the sensor array.
  • the flexible touch-sensing surface implemented using a capacitive sensor array may overlay a display panel, such as a liquid crystal display (LCD) screen to implement a touchscreen.
  • a conductive or nonconductive object applying pressure to the flexible touch- sensing surface may cause displacement of some of the sensor elements of the capacitive sensor array, which may be moved closer to the display panel, thus increasing the capacitive coupling between the display panel and the displaced sensor elements. This displacement may result in measurable changes in capacitance at any sensor elements of the capacitive sensor array that are at least partially displaced.
  • a processing device implementing the above method may receive the first and second capacitance measurements at a capacitive sensor input, then detect the presence of pressure applied to the touch-sensing surface based on the comparison between the first and second capacitance measurements.
  • the processing device may further determine a magnitude of force that is applied at the contact, and may transmit the force information to a host for further processing.
  • the capacitance measurements may be correlated with a force value stored in a lookup table.
  • the method may be used to determine a force magnitude for each of a plurality of contacts at the touch-sensing surface where force is simultaneously applied.
  • FIG. 1 illustrates a block diagram of one embodiment of an electronic system 100 including a processing device 110 that may be configured to measure capacitances from a flexible touch-sensing surface and calculate or detect the amount of force applied to the flexible touch-sensing surface.
  • the electronic system 100 includes a touch-sensing surface 116 (e.g., a touchscreen, or a touch pad) coupled to the processing device 110 and a host 150.
  • the touch-sensing surface 116 is a two-dimensional user interface that uses a sensor array 121 to detect touches on the touch-sensing surface 116.
  • the sensor array 121 includes sensor elements 121(1)-121(N) (where N is a positive integer) that are disposed as a two- dimensional matrix (also referred to as an XY matrix).
  • the sensor array 121 is coupled to pins 113(1)-113(N) of the processing device 110 via one or more analog buses 115 transporting multiple signals.
  • each sensor element 121(1)-121(N) is represented as a capacitor.
  • the capacitance sensor 101 may include a relaxation oscillator or other means to convert a capacitance into a measured value.
  • the capacitance sensor 101 may also include a counter or timer to measure the oscillator output.
  • the processing device 110 may further include software components to convert the count value (e.g., capacitance value) into a sensor element detection decision (also referred to as switch detection decision) or relative magnitude. It should be noted that there are various known methods for measuring capacitance, such as current versus voltage phase shift
  • the capacitance sensor 101 may be evaluating other measurements to determine the user interaction. For example, in the capacitance sensor 101 having a sigma-delta modulator, the capacitance sensor 101 is evaluating the ratio of pulse widths of the output, instead of the raw counts being over or under a certain threshold.
  • the processing device 110 further includes processing logic 102. Operations of the processing logic 102 may be
  • the processing logic 102 may receive signals from the capacitance sensor 101, and determine the state of the sensor array 121, such as whether an object (e.g., a finger) is detected on or in proximity to the sensor array 121 (e.g., determining the presence of the object), where the object is detected on the sensor array (e.g., determining the location of the object), tracking the motion of the object, or other information related to an object detected at the touch sensor.
  • an object e.g., a finger
  • the processing logic 102 may receive signals from the capacitance sensor 101, and determine the state of the sensor array 121, such as whether an object (e.g., a finger) is detected on or in proximity to the sensor array 121 (e.g., determining the presence of the object), where the object is detected on the sensor array (e.g., determining the location of the object), tracking the motion of the object, or other information related to an object detected at the touch sensor.
  • the processing device 110 may send the raw data or partially-processed data to the host 150.
  • the host 150 may include decision logic 151 that performs some or all of the operations of the processing logic 102. Operations of the decision logic 151 may be implemented in firmware, hardware, software, or a combination thereof.
  • the host 150 may include a high-level Application Programming Interface (API) in applications 152 that perform routines on the received data, such as
  • API Application Programming Interface
  • the processing device 110 is the host 150.
  • the processing device 110 may also include a non-sensing actions block 103.
  • This block 103 may be used to process and/or receive/transmit data to and from the host 150.
  • additional components may be implemented to operate with the processing device 110 along with the sensor array 121 (e.g., keyboard, keypad, mouse, trackball, LEDs, displays, or other peripheral devices).
  • the processing device 110 may reside on a common carrier substrate such as, for example, an integrated circuit (IC) die substrate, or a multi-chip module substrate.
  • the components of the processing device 110 may be one or more separate integrated circuits and/or discrete components.
  • the processing device 110 may be the Programmable System on a Chip (PSoCTM) processing device, developed by Cypress Semiconductor Corporation, San Jose, California.
  • the processing device 110 may be one or more other processing devices known by those of ordinary skill in the art, such as a microprocessor or central processing unit, a controller, special- purpose processor, digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable device.
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • processing device 110 may be a network processor having multiple processors including a core unit and multiple micro-engines. Additionally, the processing device 110 may include any combination of general-purpose processing device (s) and special-purpose processing device(s).
  • the electronic system 100 is implemented in a device that includes the touch-sensing surface 116 as the user interface, such as handheld electronics, portable telephones, cellular telephones, notebook computers, personal computers, personal data assistants (PDAs), kiosks, keyboards, televisions, remote controls, monitors, handheld multi-media devices, handheld video players, gaming devices, control panels of a household or industrial appliances, or other computer peripheral or input devices.
  • a device that includes the touch-sensing surface 116 as the user interface, such as handheld electronics, portable telephones, cellular telephones, notebook computers, personal computers, personal data assistants (PDAs), kiosks, keyboards, televisions, remote controls, monitors, handheld multi-media devices, handheld video players, gaming devices, control panels of a household or industrial appliances, or other computer peripheral or input devices.
  • PDAs personal data assistants
  • the electronic system 100 may be used in other types of devices. It should be noted that the components of electronic system 100 may include all the components described above. Alternatively, electronic system 100 may include only some of the components described above, or include additional components not listed herein.
  • Figure 2 is a block diagram illustrating one embodiment of a capacitive touch sensor array 121 and a capacitance sensor 101 that converts changes in measured capacitances to coordinates indicating the presence and location of touch. The coordinates are calculated based on changes in measured
  • sensor array 121 and capacitance sensor 101 are implemented in a system such as electronic system 100.
  • Sensor array 121 includes a matrix 225 of ⁇ ⁇ ⁇ electrodes (N receive electrodes and M transmit electrodes), which further includes transmit (TX) electrode 222 and receive (RX) electrode 223.
  • TX transmit
  • RX receive
  • Each of the electrodes in matrix 225 is connected with capacitance sensing circuit 101 through demultiplexer 212 and multiplexer 213.
  • Capacitance sensor 101 includes multiplexer control 211, demultiplexer 212 and multiplexer 213, clock generator 214, signal generator 215, demodulation circuit 216, and analog to digital converter (ADC) 217.
  • ADC 217 is further coupled with touch coordinate converter 218. Touch coordinate converter 218 may be implemented in the processing logic 102.
  • the transmit and receive electrodes in the electrode matrix 225 may be arranged so that each of the transmit electrodes overlap and cross each of the receive electrodes such as to form an array of intersections, while maintaining galvanic isolation from each other.
  • each transmit electrode may be capacitively coupled with each of the receive electrodes.
  • transmit electrode 222 is capacitively coupled with receive electrode 223 at the point where transmit electrode 222 and receive electrode 223 overlap.
  • Clock generator 214 supplies a clock signal to signal generator 215, which produces a TX signal 224 to be supplied to the transmit electrodes of touch sensor 121.
  • the signal generator 215 includes a set of switches that operate according to the clock signal from clock generator 214. The switches may generate a TX signal 224 by periodically connecting the output of signal generator 215 to a first voltage and then to a second voltage, wherein said first and second voltages are different.
  • the output of signal generator 215 is connected with demultiplexer 212, which allows the TX signal 224 to be applied to any of the M transmit electrodes of touch sensor 121.
  • multiplexer control 211 controls demultiplexer 212 so that the TX signal 224 is applied to each transmit electrode 222 in a controlled sequence.
  • Demultiplexer 212 may also be used to ground, float, or connect an alternate signal to the other transmit electrodes to which the TX signal 224 is not currently being applied.
  • the TX signal 224 may be presented in a true form to a subset of the transmit electrodes 222 and in complement form to a second subset of the transmit electrodes 222, wherein there is no overlap in members of the first and second subset of transmit electrodes 222.
  • the TX signal 224 applied to each transmit electrode induces a current within each of the receive electrodes. For instance, when the TX signal 224 is applied to transmit electrode 222 through demultiplexer 212, the TX signal 224 induces an RX signal 227 on the receive electrodes in matrix 225. The RX signal 227 on each of the receive electrodes can then be measured in sequence by using multiplexer 213 to connect each of the N receive electrodes to demodulation circuit 216 in sequence.
  • the mutual capacitance associated with each intersection between a TX electrode and an RX electrode can be sensed by selecting every available combination of TX electrode and an RX electrode using demultiplexer 212 and multiplexer 213.
  • multiplexer 213 may also be segmented to allow more than one of the receive electrodes in matrix 225 to be routed to additional demodulation circuits 216. In an optimized configuration, wherein there is a 1-to-l correspondence of instances of demodulation circuit 216 with receive electrodes, multiplexer 213 may not be present in the system.
  • the object When a conductive object, such as a finger, approaches the electrode matrix 225, the object causes a decrease in the measured mutual capacitance between only some of the electrodes. For example, if a finger is placed near the intersection of transmit electrode 222 and receive electrode 223, the presence of the finger will decrease the charge coupled between electrodes 222 and 223. Thus, the location of the finger on the touchpad can be determined by identifying the one or more receive electrodes having a decrease in measured mutual capacitance in addition to identifying the transmit electrode to which the TX signal 224 was applied at the time the decrease in capacitance was measured on the one or more receive electrodes. [0038] By determining the mutual capacitances associated with each intersection of electrodes in the matrix 225, the presence and locations of one or more conductive objects may be determined. The determination may be sequential, in parallel, or may occur more frequently at commonly used electrodes.
  • a finger or other conductive object may be used where the finger or conductive object causes an increase in measured capacitance at one or more electrodes, which may be arranged in a grid or other pattern.
  • a finger placed near an electrode of a capacitive sensor may introduce an additional capacitance to ground that increases the total capacitance between the electrode and ground.
  • the location of the finger can be determined based on the locations of one or more electrodes at which a change in measured capacitance is detected.
  • the induced current signal 227 is integrated by demodulation circuit 216.
  • the rectified current output by demodulation circuit 216 can then be filtered and converted to a digital code by ADC 217.
  • a series of such digital codes measured from adjacent sensor or intersections may be converted to touch coordinates indicating a position of an input on touch sensor array 121 by touch coordinate converter 218.
  • the touch coordinates may then be used to detect gestures or perform other functions by the processing logic 102.
  • the capacitance sensor 101 can be configured to detect multiple touches.
  • One technique for the detection and location resolution of multiple touches uses a two-axis implementation: one axis to support rows and another axis to support columns. Additional axes, such as a diagonal axis, implemented on the surface using additional layers, can allow resolution of additional touches.
  • a system for tracking locations of contacts on a touch-sensing surface may determine a force magnitude for each of the contacts based on the capacitance measurements from the capacitive sensor array.
  • a capacitive touch-sensing system that is also capable of
  • determining a magnitude of force applied to each of a plurality of contacts at a touch-sensing surface may be constructed from flexible materials, such as PMMA, and may have no shield between the capacitive sensor array and an LCD display panel.
  • changes in capacitances of sensor elements may be caused by the displacement of the sensor elements closer to a VCOM plane of the LCD display panel.
  • FIGS 3A and 3B illustrate embodiments of flexible touch-sensing surfaces that may be connected to a capacitance sensor such as capacitance sensor 101.
  • Touch- sensing surface 300 as illustrated in Figure 3A, includes a number of sensor elements 301 that may be part of a capacitive sensor array such as sensor array 121, as illustrated in Figure 2.
  • Touch-sensing surface 300 includes the sensor elements 301 formed on a substrate 303 and covered by an overlay 302.
  • the substrate 303 is made from a material such as Polyethylene terephthalate (PET).
  • PET Polyethylene terephthalate
  • the substrate 303 is flexible and transparent.
  • the layer of sensor elements 301 may be additionally covered with an overlay 302, which may be manufactured from a material such as PMMA.
  • the overlay 302 is also flexible and transparent.
  • the flexible touch-sensing surface 300 overlays a display panel 310, which may be a LCD display, LED display, OLED display, or some other type of display panel.
  • pressure may be applied to the touch- sensing surface 300 by an object such as stylus 320.
  • the pressure applied by the stylus 320 displaces the sensor elements 301 such that sensor elements nearer to the location where the pressure is applied are pushed closer to the display panel.
  • Touch-sensing surface 320 is similar to touch-sensing surface 310, but includes multiple layers of sensor elements 321. Touch-sensing surface 320 overlays a display panel 330, and includes two layers of sensor elements 321 formed on a substrate 323 and covered by an overlay 322. Stylus 340 applies pressure to the flexible touch-sensing surface, deforming the surface and moving at least a portion of some sensor elements closer to the display panel 330.
  • the baseline capacitance tracks changes due to fluctuations in temperature or other factors to minimize the effect of these factors on the measured capacitance.
  • a subset of the capacitance measurements that are changed by the displacement of the sensor elements can be used to detect and measure the force applied to the capacitive sensor array.
  • the deflection of some of the sensor elements 301 or 321 can result in an increase in the signal strengths measured by an ADC such as ADC 217.
  • Figure 4A illustrates a sensor array 401 of a flexible touch-sensing surface that includes row sensor elements 411-420 and column sensor elements 421-428.
  • the row and column sensor elements 411-428 are connected to a processing device 110, which measures capacitance values from each of the sensor elements 411-428.
  • the capacitance values A represent capacitance values measured from the row sensor elements 411-420 when a contact 430 by a conductive object is near or touching the sensor array 401, but is not exerting force on the sensor array 401 and is not deforming sensor array 401.
  • Capacitance values B represent capacitance values measured from the row sensor elements 411-420 when the conductive object additionally exerts a force deforming the sensor array at contact location 430.
  • Individual capacitance values from sets A and B are referenced according to the sensor elements from which they are measured, i.e., capacitance measurement 416A or 416B from row element 416.
  • the sets A and B can each be referred to as a capacitance profile associated with a particular set of contacts at the touch- sensing surface.
  • the first few profiles may have profile ratios that are comparable to those that may be caused by a conductive contact that does not apply force. This may cause difficulty in distinguishing between the conductive and non-conductive contacts.
  • a debouncing technique may be implemented so that a number of initial sampled profiles may be discarded. For example, the first one or two profiles sampled after detecting the initial contact may be discarded so that the touching object settles to its normal profile.
  • the set of capacitance values A illustrates that a contact 430 that does not apply force to the sensor array 401 and does not displace the sensor elements 411-428 results in a sharper drop in magnitude of the
  • the set of capacitance values B resulting from an object applying force to the sensor array 401 at contact 430 illustrates a more gradual drop in magnitude of the capacitance signals farther from the center of contact 430, which is caused by the displacement of the sensor elements near the contact 430.
  • a contact 430 from a conductive object not applying force results in a sharper profile.
  • the contact 430 from an object applying force and deforming the sensor array results in a wider, flatter profile.
  • even a nonconductive object applying force at contact location 430 may sufficiently increase the capacitance signals B such that the touch-sensing system may interpret the contact as a touch by a conductive object.
  • a processing device such as processing device 110 that is connected to a capacitive sensor array 401 may detect deformation caused by pressure on the sensor array 401 based on a comparison between a first capacitance measurement and a second capacitance measurement from the set of capacitance measurements taken from the row elements (or column elements) of sensor array 401.
  • the capacitance measurement with the highest magnitude may be selected as the first capacitance value, while the second capacitance value may be chosen the nth strongest capacitance signal, where n is a predetermined integer.
  • the second capacitance value may be measured from a sensor element that is a predetermined distance from the first capacitance value. For example, a first capacitance value 416 A may be compared with a second value 419A.
  • a profile ratio between the first and second capacitance values may be calculated, and an amount of force applied to the sensor elements or an amount of sensor deformation or displacement of the sensor elements may be inferred based on the profile ratio. For example, a profile ratio below a specific profile ratio threshold may be used to indicate that force is being applied to the sensor array 401, and may trigger a process to calculate the magnitude of the force applied to the flexible touch-sensing surface. In one embodiment, the calculation may be performed by the processing device 110.
  • the calculation process of the magnitude of the force allows detecting gestures based on how much force is applied to the flexible touch-sensing surface. Since deformation of the sensor array resulting from force applied by a non-conductive object causes a wider profile (smaller drop-off farther from the contact) when compared to a narrow profile (larger drop-off farther from the contact) caused by a conductive object, a shape of the profile may be used to distinguish the cases.
  • Cpeak is the first capacitance value, having the highest magnitude
  • Cn is the second capacitance value, which is chosen such that Cn is the nth strongest signal.
  • signal 416A is the first capacitance value Cpeak
  • signal 418 A may be chosen as the second capacitance value Cn, since 418A is the 4 th strongest capacitance value.
  • Cn may be a capacitance signal corresponding to a sensor element n elements away from the sensor element corresponding to the first capacitance value.
  • 412A or 420A may be chosen as the second capacitive value Cn.
  • Figure 4B illustrates a capacitance profile according to an
  • Pi and P4 may be used as the first and second capacitance values Cpeak and Cn.
  • the value for n may be chosen such that a capacitance value that is affected by the sensor element displacement, and that is less affected by proximity of a conductive object is chosen as the second capacitance value.
  • the value for n may be determined empirically by comparing profiles caused by conductive contacts and non-conductive contacts that apply force.
  • the value of n may also differ based on the pitch of the sensor elements in sensor array 401.
  • One embodiment of a touch-sensing system that is capable of detecting force may correlate values for a fourth strongest signal (P4), peak signal (Pi), and deflection (D) with a force value and a location on the touch-sensing surface.
  • P4 fourth strongest signal
  • Pi peak signal
  • D deflection
  • these values may be stored in a table such as 3D lookup table 600, illustrated in Figure 5.
  • the 3D lookup table 600 includes 16 sets of (P4, Pi, D) values such as value set 602 for each layer 601.
  • Each layer of 3D lookup table 600 represents an amount of force that may be applied to the touch-sensing surface. For example, when determining the values in the lookup table 600 empirically, each of the values in the same layer may have been determined by applying the same amount of force to the touch-sensing surface.
  • a table such as the 3D lookup table 600 may be generated by a robot that applies a target force to various locations on the touch- sensing surface using a touching object, while utilizing a force gauge to control and measure the amount of force applied to the surface by the touching object.
  • the Z-position of the touching object at the time the target force is applied or measured can be used to estimate the amount of sensor deflection.
  • the 16 (P4, Pi, D) value sets may correspond to intersections in the sensor array.
  • the value sets may only be stored for some intersections of sensor elements, or may be stored for other points distributed across the surface of the sensor array that are not associated with an intersection.
  • fewer or more than 16 value pairs are stored in each layer.
  • a 3D lookup table may also include fewer or more than 3 layers.
  • the peak (Pi) and fourth strongest (P4) capacitance values may be used to correct for shifting of any detected coordinate locations of contacts due to displacement of sensor elements by force applied to the touch- sensing surface. For example, a touch by a conductive object that displaces sensor elements may result in a different set of reported coordinates as compared to a touch in the same location that does not displace the sensor elements.
  • the P4 value of a contact may also be used to determine a magnitude of a force applied to the touch-sensing surface at the contact location.
  • the P4 value represents a signal that is affected primarily by the force applied to the contact location or the displacement of the sensor elements, and is less affected by capacitive coupling with the object contacting the touch- sensing surface.
  • P4 may be replaced by any capacitance signal that is attributable primarily to force applied to the surface or
  • the value of P4 changes monotonically with the amount of force applied to the touch-sensing surface.
  • the applied force may be represented as a function of P4 for each of the 16 value pairs (which may correspond to locations on the touch-sensing surface).
  • the lookup table may then be used to determine the force on the sensor based on a measured P4 value.
  • determining the magnitude of the applied force based on the P4 value may occur in real time, during the operation of the touch-sensing system.
  • a touch-sensing system implementing a process for detecting force applied to a touch-sensing surface may capture a capacitance profile caused by one or more contacts at the touch-sensing surface, then use the Pi and P4 values stored in a lookup table to correct the capacitance profile and obtain a corrected coordinate location for each of the one or more contacts. For example, the touch-sensing system may determine an appropriate quadratic compensation profile to adjust the measured capacitance profile, then determine a touch location based on the compensated profile.
  • the touch-sensing system may further use linear interpolation to determine P4 values corresponding to the touch location for each force layer 601.
  • the measured P4 value may lie between two interpolated P4 values corresponding to two force levels Fl and F2.
  • the touch-sensing system may perform further interpolation between the force layers Fl and F2 to more accurately correlate the measured P4 with a force value.
  • Figure 6 illustrates one force layer 900 of a 3D lookup table, such as table 600, according to an embodiment.
  • Each of the 16 points in layer 900 is associated with an X/Y coordinate location, which may correspond to a location on a touch-sensing surface.
  • the location (X0, Y0) may indicate a location of a contact at the touch-sensing surface by an object applying force to the touch- sensing surface.
  • the touch location (X0, Y0) is surrounded by four points: (XI, Yl), (X2, Yl), (XI, Y2), and (X2, Y2).
  • a contact at location (X0, Y0) causes a P4 signal that is a weighted average of the P4 values of the four surrounding points.
  • the weighting factors may be determined by the distance from the touch location (X0, Y0) to each of the four surrounding points. Defining the weighting factors in the X and Y directions as a, and ⁇ , respectively, yields Equations 2 and 3 below:
  • the interpolated P4 value at the touch location (X0, Y0) may thus be represented as Equation 4:
  • the P4 values P4 1 , P4 2 , P4 3 , and P4 4 , associated with the four surrounding points may have different values depending on the force applied to the contact. Thus, if the force being applied to the touch-sensing surface is not equal to any of the force values associated with a force layer 601, the P4 value calculated by interpolation between the four surrounding points will have some error.
  • the touch-sensing system may perform the above interpolation between the four surrounding points for all force layers 601, and may then find the closest pair of interpolated P4 values (denoted by P4,i° and P4,2°) such that P4,2° > P4(measured) > P4,i°.
  • each of P4,i° and P4,2° may be associated with the same X,Y coordinate location as the contact location being measured, and may be associated with adjacent force layers.
  • FIG. 7 illustrates the interpolation between force layers, according to one embodiment.
  • the values P4,i° and P4,2° are the P4 values for adjacent force layers Fl and F2, respectively.
  • the actual force applied to the contact (FTOUA) results in a measured P4 value of P4,m°.
  • F Touch is between the force layers Fl and F2; accordingly, F2 > F Touch > Fl.
  • a more accurate estimate of the actual force FTOU* applied to the touch-sensing surface may be determined by linear interpolation between Fl and F2. Defining a weighting factor ⁇ yields Equation below: p° _ p°
  • Equation 5 the interpolated force applied to the contact location is determined by Equation 5:
  • Equation 6 is valid for interpolation between two force layers; however, if the estimated P4 value results from an applied force that is greater than the largest recorded force or less than the smallest recorded force in the force layers, then extrapolation may be used instead. In one embodiment, the extrapolation may be based on assuming a linear relationship between the force value and the P4 value.
  • Equation 6 expresses a linear relationship between the force value and the P4 value. Equation 6 may be expressed in the form of Equation 7 below: (Equat i on 7)
  • Equation 7 expresses a linear relationship between F Touch and P4.
  • extrapolation may be used to find FTouch if the estimated value for P4 is greater than the P4 value corresponding to the largest stored force in the table.
  • Figure 8 illustrates the determination of FTOUA using extrapolation based on the largest force F2, having a corresponding P4 value of P4,2°, and the next force level below F2, designated as Fl and having a corresponding P4 value of P4,i°. Assuming that the linear relationship between the force and P4 values extends beyond F2 yields Equation 8 below:
  • Equation 8 Vi, m ° represents the P4 value measured from the capacitive touch- sensor array, which corresponds to a force value F Touch that is larger than the largest force value F2.
  • each of multiple contacts at the touch sensing surface may create its own independent capacitance profile, such that a force applied at each of the multiple contacts may be independently determined according to the above methods.
  • a touch-sensing system implementing these force detection methods may, after determining a force applied at a first contact based on the capacitance measurements, further determine a magnitude of a second force applied simultaneously with the first force at a second contact location based on a second set of capacitance measurements, including a peak capacitance value and a P4 value.
  • the touch-sensing system may determine the force applied to the second contact in a similar manner as for the force applied to the first contact.
  • the deflection induced capacitance profiles may also be used to report locations of one or more simultaneous contacts at the touch-sensing surface by either conductive or non-conductive objects.
  • the above method for determining a force applied to a contact at a touch-sensing surface may be used to determine an amount of displacement, or deflection, of a portion of the touch-sensing surface.
  • an object contacting a touch-sensing surface and applying force to the contact location may cause the part of the touch-sensing surface at which the force is applied to be displaced.
  • a displacement may be represented as a distance along an axis perpendicular to the touch-sensing surface.
  • a displacement value representing the amount of displacement caused by a force applied to a touch-sensing surface may be stored in a 3D lookup table, such as table 600, as illustrated in Figure 5.
  • the displacement values may be determined empirically by applying a known force to the touch-sensing surface, then measuring the resulting displacement and storing the displacement value for each of a number of locations. The displacement value can then be determined in a similar manner as the force.
  • FIG. 9 illustrates an embodiment of a force detection process 900 that may be implemented in a touch-sensing system, such as touch-sensing 100 of Figure 1.
  • force detection process 900 begins at block 901.
  • the touch-sensing system may receive a plurality of capacitance measurements affected by one or more contacts at the touch-sensing surface.
  • a contact 430 at the touch-sensing surface may cause changes in capacitances of sensor elements in the sensor array 401, resulting a set of capacitance values such as capacitance values B.
  • a capacitance sensor of the touch-sensing system may measure these capacitances, which may then be received by processing logic.
  • the process 900 continues at block 903.
  • the touch-sensing system determines a location for each of the one or more contacts based on the capacitance measurements received at block 901. For example, the magnitudes of capacitance values for the row and column sensor elements may be used to calculate a centroid location of a contact. From block 903, the process 900 continues at block 905.
  • the touch-sensing system selects a capacitance
  • the capacitance value may be selected based on a ranking of the capacitance measurements in a capacitance profile.
  • the selected capacitance measurement may be a P4 value, representing the fourth strongest capacitance signal from among the plurality of capacitance measurements in the profile.
  • the selected capacitance measurement may be selected based on a position relative to a peak capacitance measurement Cpeak. From block 905, the process 900 continues at block 907.
  • the touch-sensing system may use a lookup table to determine a magnitude for each force applied at the one or more contacts based on the contact location and the selected capacitance measurement.
  • a lookup table such as 3D lookup table 600 may be used to correlate the location of a contact and a selected capacitance measurement, such as a P4 value, of the contact with a force value.
  • the touch-sensing system may interpolate or extrapolate within a layer, such as a layer 601, or between layers to obtain a more accurate force value. From block 907, the process 900 continues at block 909.
  • the touch-sensing system uses a lookup table to determine a displacement caused by each of the forces applied at the one or more contacts based on the contact location and the selected capacitance measurement.
  • a 3D lookup table such as table 600 may correlate a displacement value with the location of a contact and a selected capacitance measurement, such as a P4 value.
  • the displacement values may be stored in the same 3D lookup table as force values of block 907.
  • the touch-sensing system may similarly perform interpolation or extrapolation within and between layers to more accurately determine a displacement value. From block 909, the process 900 continues at block 911.
  • the touch-sensing system may report the force and/or displacement values associated with each contact to a host device.
  • processing logic 102 of a touch-sensing system may report the location, force, and displacement values to a host 150. From block 911, the process 900 may continue back to block 901.
  • the touch-sensing system may repeat the operations associated with blocks 901 to 911 to continuously update and track the locations of contacts at the touch-sensing surface, the forces applied to the touch-sensing surface at the contacts, and the amounts of displacement of the touch-sensing surface at each contact.
  • Embodiments of the present invention include various operations. These operations may be performed by hardware
  • the term “coupled to” may mean coupled directly or indirectly through one or more intervening components. Any of the signals provided over various buses described herein may be time multiplexed with other signals and provided over one or more common buses. Additionally, the interconnection between circuit components or blocks may be shown as buses or as single signal lines. Each of the buses may alternatively be one or more single signal lines and each of the single signal lines may alternatively be buses.
  • Certain embodiments may be implemented as a computer program product that may include instructions stored on a computer-readable medium. These instructions may be used to program a general-purpose or special-purpose processor to perform the described operations.
  • a computer-readable medium includes any mechanism for storing or transmitting information in a form (e.g., software, processing application) readable by a machine (e.g., a computer).
  • the computer-readable storage medium may include, but is not limited to, magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto-optical storage medium; read-only memory (ROM); random-access memory (RAM); erasable programmable memory (e.g., EPROM and EEPROM); flash memory, or another type of medium suitable for storing electronic instructions.
  • magnetic storage medium e.g., floppy diskette
  • optical storage medium e.g., CD-ROM
  • magneto-optical storage medium e.g., magneto-optical storage medium
  • ROM read-only memory
  • RAM random-access memory
  • EPROM and EEPROM erasable programmable memory
  • flash memory or another type of medium suitable for storing electronic instructions.
  • information transferred between computer systems may either be pulled or pushed across the transmission medium connecting the computer systems.

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Abstract

La présente invention concerne un procédé permettant de détecter la puissance d'une force appliquée sur une matrice de capteurs capacitifs. Ce procédé consiste à recevoir une pluralité de mesures de capacitance modifiées par un contact exercé sur une surface tactile. Le procédé consiste ensuite à déterminer la puissance d'une force appliquée sur un point de contact de la surface tactile, en fonction dudit point de contact et d'une mesure de capacitance de la première pluralité de mesures de capacitance.
PCT/US2011/053638 2010-10-12 2011-09-28 Capteur tactile hybride capacitif à détection de force WO2012050875A1 (fr)

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US39203410P 2010-10-12 2010-10-12
US61/392,034 2010-10-12
US13/091,132 US9459736B2 (en) 2010-10-12 2011-04-21 Flexible capacitive sensor array
US13/091,132 2011-04-21
US201161522151P 2011-08-10 2011-08-10
US61/522,151 2011-08-10

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014036532A1 (fr) * 2012-08-31 2014-03-06 Analog Devices, Inc. Système de geste capacitif et de détection d'environnement destiné à des dispositifs mobiles
US8744418B2 (en) 2012-08-31 2014-06-03 Analog Devices, Inc. Environment detection for mobile devices
WO2015080696A1 (fr) * 2013-11-26 2015-06-04 Rinand Solutions Llc Auto-étalonnage de capteurs de force et compensation de l'inertie
CN106371647A (zh) * 2015-07-24 2017-02-01 高深公司 触摸压力灵敏度修正方法及计算机可读记录介质
US9692875B2 (en) 2012-08-31 2017-06-27 Analog Devices, Inc. Grip detection and capacitive gesture system for mobile devices
US10139869B2 (en) 2014-07-23 2018-11-27 Analog Devices, Inc. Capacitive sensors for grip sensing and finger tracking
US10936128B2 (en) 2013-02-12 2021-03-02 Sony Corporation Sensor device, input device, and electronic apparatus

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090273579A1 (en) * 2008-04-30 2009-11-05 N-Trig Ltd. Multi-touch detection
US20100073320A1 (en) * 2008-09-23 2010-03-25 Au Optronics Corp. Multi-touch positioning method for capacitive touch panel
EP2214082A1 (fr) * 2009-01-29 2010-08-04 Sensitive Object Dispositif de détection de toucher doté d'une fonction de maintien de touche et procédé correspondant
US20100231548A1 (en) * 2009-03-10 2010-09-16 William Henry Mangione-Smith Touch-sensitive display device and method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090273579A1 (en) * 2008-04-30 2009-11-05 N-Trig Ltd. Multi-touch detection
US20100073320A1 (en) * 2008-09-23 2010-03-25 Au Optronics Corp. Multi-touch positioning method for capacitive touch panel
EP2214082A1 (fr) * 2009-01-29 2010-08-04 Sensitive Object Dispositif de détection de toucher doté d'une fonction de maintien de touche et procédé correspondant
US20100231548A1 (en) * 2009-03-10 2010-09-16 William Henry Mangione-Smith Touch-sensitive display device and method

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014036532A1 (fr) * 2012-08-31 2014-03-06 Analog Devices, Inc. Système de geste capacitif et de détection d'environnement destiné à des dispositifs mobiles
US8744418B2 (en) 2012-08-31 2014-06-03 Analog Devices, Inc. Environment detection for mobile devices
US9692875B2 (en) 2012-08-31 2017-06-27 Analog Devices, Inc. Grip detection and capacitive gesture system for mobile devices
US10382614B2 (en) 2012-08-31 2019-08-13 Analog Devices, Inc. Capacitive gesture detection system and methods thereof
US10936128B2 (en) 2013-02-12 2021-03-02 Sony Corporation Sensor device, input device, and electronic apparatus
WO2015080696A1 (fr) * 2013-11-26 2015-06-04 Rinand Solutions Llc Auto-étalonnage de capteurs de force et compensation de l'inertie
US10139959B2 (en) 2013-11-26 2018-11-27 Apple Inc. Self-calibration of force sensors and inertial compensation
US10139869B2 (en) 2014-07-23 2018-11-27 Analog Devices, Inc. Capacitive sensors for grip sensing and finger tracking
CN106371647A (zh) * 2015-07-24 2017-02-01 高深公司 触摸压力灵敏度修正方法及计算机可读记录介质
EP3327559A4 (fr) * 2015-07-24 2019-03-13 Hideep Inc. Procédé de correction de sensibilité de pression tactile et support d'enregistrement lisible par ordinateur
CN106371647B (zh) * 2015-07-24 2019-08-02 高深公司 触摸压力灵敏度修正方法及计算机可读记录介质
US10394364B2 (en) 2015-07-24 2019-08-27 Hideep Inc. Touch pressure sensitivity correction method and computer-readable recording medium

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