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WO2024189360A1 - Capteur et procédé - Google Patents

Capteur et procédé Download PDF

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Publication number
WO2024189360A1
WO2024189360A1 PCT/GB2024/050685 GB2024050685W WO2024189360A1 WO 2024189360 A1 WO2024189360 A1 WO 2024189360A1 GB 2024050685 W GB2024050685 W GB 2024050685W WO 2024189360 A1 WO2024189360 A1 WO 2024189360A1
Authority
WO
WIPO (PCT)
Prior art keywords
sensor
shield
capacitive sensing
sensing electrode
electrically conductive
Prior art date
Legal status (The legal status 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 status listed.)
Pending
Application number
PCT/GB2024/050685
Other languages
English (en)
Inventor
Jean Mugiraneza
Tanaka Kohei
Wilhelmus Van Lier
Toru Sakai
Henricus Derckx
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Touch Biometrix Ltd
Sharp Display Technology Corp
Original Assignee
Touch Biometrix Ltd
Sharp Display Technology Corp
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
Application filed by Touch Biometrix Ltd, Sharp Display Technology Corp filed Critical Touch Biometrix Ltd
Publication of WO2024189360A1 publication Critical patent/WO2024189360A1/fr
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/08—Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes
    • G06K7/081—Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes electrostatic, e.g. by detecting the charge of capacitance between electrodes
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; 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
    • G06F3/0446—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
    • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
    • G06V40/12—Fingerprints or palmprints
    • G06V40/13—Sensors therefor
    • G06V40/1306—Sensors therefor non-optical, e.g. ultrasonic or capacitive sensing

Definitions

  • the present disclosure relates to the field of sensors and sensing methods.
  • the present disclosure relates to the field of capacitive sensors, such as capacitive touch sensors, as well as methods of operating such sensors.
  • PCT publications WO 2020/178605 and WO 2022/043699 disclose different examples of capacitive biometric skin contact sensors. These sensors are operable to obtain capacitance measurements for a sensor array which spans a large area. Based on these capacitance values, biometric data may be obtained for the user contacting the sensor. For example, a difference between ridges and valleys in a user’s skin contours may be identified based on the differences in measured capacitance across the sensor array. Such sensors may implement a biometric authentication by comparing an obtained distribution of skin contours to a known distribution of skin contours. For example, the sensor may be a fingerprint sensor which may identify users based on their fingerprints. For both prior art publications, the specific sensor pixel designs disclosed therein are chosen to provide high signal to noise ratios for measurements obtained using those sensor pixels.
  • the present disclosure aims to provide improvements to such prior art sensors.
  • a capacitive sensor comprising an array of sensor pixels, wherein each sensor pixel comprises: a capacitive sensing electrode; and a shield.
  • the shield is electrically conductive and arranged to electrically shield the capacitive sensing electrode from parasitic coupling with other elements of the sensor.
  • the sensor is configured to maintain the shield at a shielding voltage while a read-out signal is being obtained from the sensor pixel.
  • the sensor is configured to maintain the shield at the shielding voltage so that a parasitic capacitive coupling between the shield and the capacitive sensing electrode will occur with one side of that effective capacitor being maintained at a known voltage. That is, the shield will be maintained at the shielding voltage.
  • the other side of that effective capacitor (the capacitive sensing electrode) will store an amount of charge indicative of the proximity to that electrode of a conductive object to be sensed.
  • the amount of charge stored on that capacitive sensing electrode may also be influenced by its capacitive coupling with the shield.
  • the parasitic coupling between the capacitive sensing electrode and the shield may be a known quantity.
  • the contribution of this parasitic coupling to the amount of charge stored on the capacitive sensing electrode may also be known. This contribution may be compensated for.
  • the sensor may determine what the contribution to that amount of charge is by the capacitive coupling. In turn, this may enable a better determination of the contribution to the amount of charge stored on the capacitive sensing electrode which is due to the proximity of the conductive object to be sensed.
  • Embodiments may enable an effective increase in the signal to noise ratio which may be obtained from read-out signals from the array of sensor pixels. Also, this may enable the provision of a greater dynamic range for measurements obtained using the sensor. In other words, for each given read-out signal, the contribution to that read-out signal from unknown and/or unquantifiable sources of noise will be reduced. Instead, noise in the signal associated with capacitive coupling between the capacitive sensing electrode and the shield will be a known quantity which can be compensated for. Thus, this arrangement may increase signal to noise for measurements obtained from the sensor . A greater dynamic range may also be obtained from the sensor, as a greater response within each read-out signal to changes in charge stored on the capacitive sensing electrode may be derived from the obtained read-out signals.
  • the voltage source may be a DC voltage source. It may be a voltage source which is also used to provide a voltage to other components of the sensor array, it may be a separate voltage source for the shield, or it may be an electrical ground.
  • the sensor may be configured to simultaneously activate a sensor pixel for outputting a read-out signal and connect the shield for that sensor pixel to a shielding reference voltage source.
  • the senor may be configured to apply one or more electrical signals to activate a sensor pixel, and wherein said application of electrical signals also acts to maintain the shield at the shielding voltage.
  • the sensor may be configured to electrically connect the shield to a shielding voltage source so that the shielding voltage source may charge/discharge/neither the shield to the shielding voltage, and then maintain the shield at the shielding voltage while the read-out signal is obtained from the sensor pixel.
  • the sensor may comprise a plurality of conductive lines across the array.
  • the shield may be connected to at least one of said conductive lines.
  • the at least one conductive line may electrically connect the shield to a controlled voltage source.
  • the controlled voltage source may be configured so that, once electrically connected to the shield, the controlled voltage source will control the shield to be at a selected voltage (e.g. a fixed constant voltage).
  • the at least one conductive line may comprise: (i) one or more scan lines, (ii) one or more ground lines, or (iii) one or more voltage supply lines.
  • the shield may overlie said other elements of the sensor.
  • said other elements may be located beneath (e.g. vertically underneath the shield).
  • a top surface of the sensor may be a contact surface to contacting by an object to be sensed.
  • the shield may be provided in the same layer as the capacitive sensing electrode.
  • the shield may be provided in a layer between the capacitive sensing electrode and said other elements of the sensor.
  • the capacitive sensing electrode may overlie the shield.
  • the shield may vertically separate the capacitive sensing electrode from said other elements of the sensor.
  • a single electrically conductive element may provide the shield for a plurality of sensor pixels.
  • the single electrically conductive element may provide the shield for all of the sensor pixels in the array, e.g. the sensor array may have one shield which electrically shields all of the capacitive sensing electrodes in the array.
  • the single electrically conductive element may be connected to a plurality of conductive lines across the sensor array.
  • the single electrically conductive element may provide the shield for all of the sensor pixels in a row, and wherein the shield may be connected to a scan line for said row.
  • the sensor may be a capacitive touch sensor.
  • Each read-out signal may be indicative of an amount of charge stored on a capacitive sensing electrode.
  • Each read-out signal may provide an indication of the proximity to the capacitive sensing electrode of an object to be sensed.
  • the sensor may be a capacitive biometric skin contact sensor.
  • the sensor may be configured to operate in a first mode in which the shield is used to perform capacitive contact sensing. In response to obtaining an indication of contact when operating in the first mode, the sensor may be configured to switch operation into a second mode in which the capacitive sensing electrode is used to perform capacitive biometric skin contact sensing.
  • the shield of each sensor pixel may be substantially opaque to visible and/or ultraviolet light.
  • the shield of each sensor pixel may be arranged to provide shielding from electromagnetic and/or electrostatic interference.
  • the shield may be coupled to each of a high and low voltage rail via one or more diodes arranged to provide electrical interference protection.
  • the sensor pixel circuitry may comprise at least one thin film transistor, TFT.
  • the shield may be arranged to electrically shield the capacitive sensing electrode from parasitic coupling with said TFT.
  • TFTs of the present disclosure may comprise at least one of the following types of TFT: (i) Oxide, such as Indium Gallium Zinc Oxide (‘IGZO’), (ii) Amorphous Silicon (‘aSi’), (iii) (Low Temperature) Poly Silicon (‘LTPS’/’pSi’), (iv) an LTPS and Oxide combination such as LTPO, (v) Organic.
  • Oxide such as Indium Gallium Zinc Oxide (‘IGZO’
  • aSi Amorphous Silicon
  • LTPS Low Temperature Poly Silicon
  • LTPS Low Temperature Poly Silicon
  • the sensor may comprise an array of sensor pixels, where each sensor pixel includes one or more thin film transistors (‘TFTs’) and a capacitive sensing electrode.
  • the sensor pixels may be arranged in an active-matrix array in which the sensor may be operable to address each pixel by applying a scanning signal to that pixel.
  • Each pixel being addressed may also receive a supply voltage from a supply line.
  • Each pixel being addressed may output a read-out signal to a readout line.
  • the read-out signal may be indicative of the proximity of a conductive body to be sensed to the capacitive sensing electrode of that sensor pixel.
  • the sensor may comprise read-out circuitry configured to process said read-out signals.
  • each sensor pixel may include at least one TFT which controls the read-out signals from that sensor.
  • This may comprise a ‘sense TFT’ arranged for outputting read-out signals to a read-out line.
  • the sense TFT may output a read-out signal to the read-out line to which it is connected.
  • the capacitive sensing electrode may be coupled to a gate region of the sense TFT, and so a magnitude of the read-out signal from the sense TFT to the read-out line may be influenced by the effective capacitance of the capacitive sensing electrode (i.e. which may thus be indicative of the proximity of the conductive body to be sensed to that capacitive sensing electrode).
  • the sensor may be configured to perform this process iteratively for different sensor pixels so that a read-out signal has been obtained for each sensor pixel in the array.
  • each sensor pixel comprises: (i) a capacitive sensing electrode, and (ii) a shield, wherein the shield is electrically conductive and arranged to electrically shield the capacitive sensing electrode from parasitic coupling with other elements of the sensor.
  • the method comprises maintaining the shield at a shielding voltage while a read-out signal is being obtained from the sensor pixel to provide said electrical shielding of the capacitive sensing electrode.
  • the shield may be connected to a controlled voltage source to maintain the shield at the shielding voltage.
  • the shield may be connected to the controlled voltage source by one or more conductive lines across the sensor array.
  • the shield may be connected to: (i) one or more scan lines, (ii) one or more ground lines, or (iii) one or more voltage supply lines, to connect the shield to the controlled voltage source to maintain the shield at the shielding voltage while the read-out signal is being obtained from the sensor pixel.
  • Methods may comprise using the shield to obtain an indication of contact with the sensor array, and then using the capacitive sensing electrode to perform biometric sensing after an indication of contact has been detected.
  • Methods may comprise simultaneously maintaining the shield of a plurality of sensor pixels at the shielding voltage.
  • aspects of the present disclosure may comprise one or more computer program products comprising computer program instructions configured to control a capacitive biometric skin contact sensor to perform any of the methods disclosed herein.
  • Fig. 1 is a schematic diagram illustrating an array of sensor pixels for a capacitive sensor.
  • Fig. 2a is a schematic diagram illustrating a cross-sectional view of a sensor pixel.
  • Fig. 2b is a schematic diagram illustrating a cross-sectional view of a sensor pixel.
  • Fig. 3 is a schematic diagram illustrating an array of sensor pixels for a capacitive sensor.
  • Fig. 4a is a schematic diagram illustrating an array of sensor pixels for a capacitive sensor.
  • Fig. 4b is a schematic diagram illustrating an array of sensor pixels for a capacitive sensor.
  • Fig. 5 is a schematic diagram illustrating an array of sensor pixels for a capacitive sensor.
  • the present disclosure relates to the use of an active shield for a capacitive sensor pixel.
  • the shield is arranged to inhibit a capacitive sensor electrode in the sensor pixel from coupling capacitively with other nearby elements of the sensor, such as other electrically conductive components of the sensor pixel itself. Instead, it is the shield which is arranged to couple capacitively with such other electrically conductive elements of the sensor. While a read-out signal is obtained from the sensor pixel, the shield is maintained at a fixed, known voltage.
  • a value for any capacitive coupling between the capacitive sensing electrode and the shield may be determined accurately, as the shield voltage is known and fixed, and the shield inhibits the capacitive sensing electrode from capacitively coupling with other electrically conductive elements which are at unknown voltages. This may therefore reduce an amount of noise present in read-out signals indicative of the charge stored on the capacitive sensing electrode of the sensor pixel.
  • Example sensor pixel designs will be described in relation to Figs. 2a and 2b, but first an example sensor array will be described with reference to Fig. 1.
  • Fig. 1 shows a plan view of a portion of a sensor array 10 comprising a plurality of sensor pixels 100.
  • Each sensor pixel 100 is shown as having a capacitive sensing electrode 110.
  • other components of the sensor array 10 including those in each sensor pixel 100 are not shown in Fig. 1.
  • the sensor array 10 contains a plurality of rows of sensor pixels 100 and a plurality of columns of sensor pixels 100.
  • Each sensor pixel 100 may provide its own sensing area on the sensor array 10 (i.e. each sensor pixel 100 may be configured to provide sensing for a subset of the total area of the array 10).
  • the capacitive sensing electrode 110 of each sensor pixel 100 may take up a majority of the area of its sensor pixel 100 (when viewed in plan). By increasing the area covered by a capacitive sensing electrode 110, a greater amount of charge may be stored on that electrode 110.
  • the area covered by each individual electrode 110 may also be limited so that the spatial resolution of the capacitive sensor may be sufficiently high to provide biometric sensing (e.g. for identifying contours of a user’s skin).
  • Each sensor pixel 100 is configured to output a read-out signal indicative of an amount of charge stored on its capacitive sensing electrode 110. In turn, this may provide an indication of the proximity to the capacitive sensing electrode 110 of a conductive object to be sensed.
  • the sensor array 10 may comprise an active-matrix array of sensor pixels 100. Each sensor pixel 100 may be selectively activated, and a read-out signal from that sensor pixel 100 obtained.
  • the sensor may be configured to activate a plurality of different sensor pixels 100 at one time. For example, the sensor may be configured to activate each sensor pixel 100 in a row at a time. Read-out signals may then be obtained from sensor pixels 100 in that row. For example, read-out signals may be obtained from some or all of the sensor pixels 100 in that row.
  • Each sensor pixel 100 may comprise one or more electrical components configured for outputting a read-out signal indicative of the amount of charge stored on the capacitive sensing electrode 110.
  • the read-out signal may be an electrical signal such as a current or voltage signal.
  • the read-out signal may be in the form of a current signal, where e.g. a magnitude of the current of that signal provides an indication of the amount of charge stored.
  • Each sensor pixel 100 may include one or more thin film transistors (‘TFTs’).
  • Each sensor component may also include other types of electrical components, such as a capacitor.
  • the sensor array 10 may comprise a plurality of electrically conductive lines connected to the sensor pixels 100 for activating the sensor pixels 100, and for transmitting read-out signals therefrom to read-out circuitry of the sensor.
  • Each sensor pixel 100 may comprise a multi-layered pixel stack.
  • the pixel stack for each sensor pixel 100 may comprise a plurality of electrically conductive layers (e.g. metallisation layers). The different electrical components may be provided across multiple electrically conductive layers.
  • Each electrically conductive layer may be separated from an adjacent electrically conductive layer by an intervening layer.
  • the intervening layer(s) may comprise an insulator material.
  • the stack may also comprise semiconductor material for providing one or more TFTs of the stack.
  • a top surface of the sensor may be arranged for contacting by an object to be sensed.
  • the capacitive sensing electrode 110 for each sensor pixel 100 may be provided in the topmost electrically conductive layer of the stack (e.g.
  • the other electrically conductive components in the stack may be provided in one or more electrically conductive layers beneath the topmost electrically conductive layer (e.g. in layers beneath the capacitive sensing electrode 110).
  • Sensors of the present disclosure include a shield arranged for electrically shielding the capacitive sensing electrode 110 from parasitic coupling with other elements of the sensor.
  • the shield may electrically shield the capacitive sensing electrode 110 of a sensor pixel 100 from the other components (e.g. one or more transistors and/or a capacitor) within that sensor pixel.
  • the shield may be arranged so that it capacitively couples with those sensor elements itself.
  • the sensor is configured to maintain the shield at a shielding voltage so that any capacitive coupling between the capacitive sensing electrode 110 and the shield will occur with the shield at a known, reference voltage.
  • the sensor pixel is arranged so that the capacitive sensing electrode 110 is laterally offset from electrical components with which it could capacitively couple, and those components are laterally aligned with the shield.
  • the sensor pixel is arranged so that the shield is in an intervening layer between the capacitive sensing electrode 110 and those components.
  • Fig. 2a shows a cross-sectional view of a sensor pixel 100.
  • the sensor pixel stack for the sensor pixel 100 is shown as comprising two electrically conductive layers: first electrically conductive layer 105a and second electrically conductive layer 105b. For simplicity, no other electrically conductive layers are shown, nor are any intervening layers shown.
  • the sensor pixel 100 includes a substrate 101 , an electrically conductive component 102, a capacitive sensing electrode 110 and a shield 120. Also shown is a shield connector 122. Although not shown explicitly in Fig. 2a, the shield connector 122 is connected to one or more electrically conductive components, such as a reference voltage source (thereby to electrically connect the shield 120 to said component(s), e.g. for maintaining the shield at the shielding voltage).
  • the substrate 101 provides a base layer for the sensor pixel, with the remaining layers of the stack are provided on top of this base layer.
  • the first electrically conductive layer 105a is in a lower layer than the second electrically conductive layer 105b.
  • the electrically conductive component 102 is at least partially provided in the first electrically conductive layer 105a.
  • the first electrically conductive layer 105a may comprise a metallisation layer.
  • the first electrically conductive layer 105a may have been formed from an area of an electrically conductive material, such as a metal, which was deposited on top of a layer beneath it, e.g. onto the substrate 101 itself.
  • the sensor pixel 100 may be arranged so that the electrically conductive component 102 (and any other electrically conductive components not shown) are provided in a first area of the sensor pixel.
  • the first area may be relatively small compared to the area of the sensor pixel 100 as a whole.
  • the first area may occupy less than half of the total area for the sensor pixel.
  • the electrically conductive component 102 may comprise a TFT. It is to be appreciated that, in practice, a TFT may be provided using two or more electrically conductive layers, but for simplicity this is just shown as one component in one electrically conductive layer.
  • the electrically conductive component 102 may be arranged towards a periphery of the sensor pixel. For example, the electrically conductive component 102 may be located closer to a periphery (e.g. perimeter) of the sensor pixel 100 than to the centre of that sensor pixel.
  • the shield 120 and the capacitive sensing electrode 110 are provided in the second electrically conductive layer 105b.
  • the second electrically conductive layer 105b is above the first electrically conductive layer 105a.
  • the shield 120 and the capacitive sensing electrode 110 are separated from each other in the second electrically conductive layer 105b (e.g. they do not touch).
  • the shield 120 may occupy a smaller area of the second electrically conductive layer 105b than the capacitive sensing electrode 110.
  • the capacitive sensing electrode 110 may span a majority of the area of the second electrically conductive layer 105b.
  • the second electrically conductive layer 105b may comprise a metallisation layer.
  • the second electrically conductive layer 105b may have been formed from an area of an electrically conductive material, such as a metal, which was deposited on top of a layer beneath it, e.g. onto an insulator layer.
  • the shield 120 overlies the electrically conductive component 102. That is, the shield 120 is located above the electrically conductive component 102. There may be one or more layers between the shield 120 and the electrically conductive component 102. The shield 120 may cover the entirety (or at least a majority) of the first area. In other words, the electrically conductive component 102 may be completely overlayed by the shield 120. For example, when viewed in plan, the area occupied by the electrically conductive component 102 may completely fall within the area covered by the shield 120. It will be appreciated that, while only one electrically conductive component 102 is shown in Fig. 2a, in examples where there are a plurality of electrically conductive components, these may all be overlayed by the shield 120 (e.g.
  • the capacitive sensing electrode 110 does not overlie the electrically conductive component 102. For example, there may be no electrically conductive components beneath the capacitive sensing electrode 110, or at least the only electrically conductive components underneath the capacitive sensing electrode 110 may be such that any capacitive coupling between them and the capacitive sensing electrode 110 would be negligible.
  • the shield 120 is arranged to be vertically above the electrically conductive component 102 (e.g. when the sensor is arranged upright with the second electrically conductive layer 105b above the first electrically conductive layer 105a).
  • the shield 120 may completely encompass the lateral extent of the electrically conductive component 102.
  • the capacitive sensing electrode 110 may be laterally offset from the electrically conductive component 102. There may be no lateral overlap between the capacitive sensing electrode 110 and the electrically conductive component 102. For example, there may be no electrically conductive elements vertically underneath the capacitive sensing electrode 110. It will be appreciated that one or more conductive connections may be provided for electrically connecting components in the second electrically conductive layer 105b with components in the first electrically conductive layer 105a.
  • each sensor pixel 100 may include one or more conductive vias for providing electrical connections between different electrically conductive layers. Only one of these is shown in Fig. 2a, which is the shield connector 122.
  • the shield connector 122 electrically connects the shield 120 to one or more other electrically conductive components of the sensor for enabling the shield 120 to be maintained at the shielding voltage.
  • the shield connector 122 electrically connects the shield 120 to a reference voltage source.
  • the shield connector 122 is shown as leading away from the sensor pixel 100 (on top of the substrate 101) for providing this connection to the reference voltage source (although the reference voltage source is not shown in Fig. 2a). Any suitable electrical connection may be used to enable the shield 120 to be connected to the reference voltage source (and thus to hold the shield 120 at a reference voltage).
  • the sensor pixel 100 is arranged to output a read-out signal indicative of an amount of charge stored on the capacitive sensing electrode 110.
  • the electrically conductive component 102 is configured for outputting a read-out signal indicative of an amount of charge stored on the capacitive sensing electrode 110.
  • the sensor may be configured to provide one or more electrical signals to the sensor pixel 100 to cause the sensor pixel 100 to output the read-out signal.
  • the sensor may apply a scanning signal to the sensor pixel 100 and/or provide a supply voltage to the sensor pixel.
  • the sensor pixel 100 may be configured to output the read-out signal.
  • the sensor is configured to maintain the shield 120 at a reference voltage.
  • the shield connector 122 is arranged to electrically connect the shield 120 to a reference voltage source.
  • the shield 120 may therefore be maintained at a reference voltage associated with the reference voltage source.
  • the sensor may be configured to selectively maintain the shield 120 at the reference voltage.
  • the sensor may selectively connect the shield 120 to the reference voltage source.
  • the sensor is configured so that the shield 120 will be connected to the reference voltage source while the sensor pixel 100 is being activated to provide a read-out signal therefrom.
  • the shield 120 is arranged to capacitively couple with the electrically conductive component 102.
  • the shield 120 and the electrically conductive component 102 may effectively be arranged to each provide one plate of a capacitor (e.g. where the two plates are separated by any intervening layers, such as an insulator layer).
  • the shield 120 may be arranged to capacitively couple with any suitable component (e.g. any part of the sensor pixel 100 which may store some charge, and thus may provide a capacitive coupling). For simplicity, this is shown as the electrically conductive component 102, but that component could have additional or alternative electrical properties.
  • the shield 120 will be maintained at its reference voltage, and so that plate of the effective capacitor will be at a known reference voltage.
  • the shield 120 is maintained at the reference voltage while a read-out signal is obtained from the sensor pixel, and so a voltage of the shield 120 during that period may be known.
  • the capacitive sensing electrode 110 is arranged away from the electrically conductive component 102 so that no (or minimal) capacitive coupling occurs between the two. Instead, the capacitive coupling will be between the shield 120 and the electrically conductive element. In other words, the sensor is arranged to cause a controlled (parasitic) capacitive coupling between the shield 120 and the electrically conductive component 102.
  • This controlled capacitive coupling for the shield 120 is selected to inhibit parasitic capacitive coupling between the capacitive sensing electrode 110 and the electrically conductive component 102 (or any other relevant components which may be at variable and unknown voltages, and would thus provide unknown parasitic effects).
  • the sensor pixel 100 is activated for obtaining a read-out signal therefrom.
  • activating the sensor pixel 100 comprises applying a scanning signal to that sensor pixel 100 to selectively turn that sensor pixel 100 on, and also providing a supply voltage to that sensor pixel 100 for the sensor to then output the read-out signal.
  • Activating the sensor pixel 100 also comprises electrically connecting the shield 120 to the reference voltage source. This causes the shield 120 to be charged to the reference voltage associated with the reference voltage source (e.g. current may flow through the shield connector 122 so that the shield 120 is at the reference voltage).
  • the shield 120 will capacitively couple with the electrically conductive component 102, but the capacitive sensing electrode 110 will not.
  • the sensor pixel 100 outputs its read-out signal for processing by read-out circuitry of the sensor, from which a proximity to the capacitive sensing electrode 110 of the object to be sensed may be determined.
  • Fig. 2b shows a sensor pixel 100.
  • the sensor pixel stack for the sensor pixel 100 is shown as comprising three electrically conductive layers: first electrically conductive layer 105a, second electrically conductive layer 105b and third electrically conductive layer 105c. For simplicity, no other electrically conductive layers are shown, nor are any intervening layers shown.
  • the sensor pixel 100 of Fig. 2b includes a substrate 101 , an electrically conductive component 102, a capacitive sensing electrode 110 and a shield 120.
  • a shield connector 122 is shown in Fig. 2b as well.
  • the sensor pixel 100 of Fig. 2b is similar to that of Fig. 2a, except that in Fig. 2b the shield 120 is provided in a different electrically conductive layer to the capacitive sensing electrode 110.
  • the shield 120 is provided in an electrically conductive layer beneath the electrically conductive layer which provides the capacitive sensing electrode 110.
  • the shield 120 is provided in the second electrically conductive layer 105b and the capacitive sensing electrode 110 is provided in the third electrically conductive layer 105c.
  • the capacitive sensing electrode 110 is in the uppermost electrically conductive layer of the sensor pixel.
  • the shield 120 is in a layer between the uppermost (third) layer and the lower (first) layer, e.g. the shield 120 is in a layer vertically between the capacitive sensing electrode 110 and the electrically conductive component 102.
  • the shield 120 overlies the electrically conductive component 102.
  • the arrangement of the first electrically conductive layer 105a need not be the same as for Fig. 2a.
  • any electrically conductive elements in the first electrically conductive layer 105a could be spatially distributed across the entire area of the sensor pixel, or they may span only a periphery of the area of the sensor pixel.
  • the shield 120 may span an area of the sensor pixel 100 which covers any electrically conductive components in the layers beneath it.
  • the first electrically conductive component 102 may fall entirely within the lateral extent of the shield 120 (in a layer above it).
  • the shield 120 may span the majority of the second electrically conductive layer 105b, e.g. it may span all of it.
  • the electrical shield 120 may span across more than one sensor pixel.
  • the lateral extent of the shield 120 may encompass the majority of the area of the sensor pixel which is covered by electrically conductive components.
  • the lateral extent of the shield 120 may encompass all electrically conductive components in layers beneath it.
  • the shield 120 may include one or more openings through which a conductive connection between the capacitive sensing electrode 110 and other components of the circuitry passes.
  • a conductive via may pass through an opening in the shield 120 from the capacitive sensing electrode 110 to a component in a lower layer of the sensor pixel.
  • the capacitive sensing electrode 110 overlies the shield 120.
  • the shield 120 may completely separate (spatially) the capacitive sensing electrode 110 from any electrically conductive components beneath the shield 120.
  • the shield 120 may be the same size as, smaller than, or larger than, the capacitive sensing electrode 110.
  • the shield 120 may be sized so that it covers all of the electrically conductive components in layers beneath it.
  • the shield 120 in the sensor pixel 100 of Fig. 2b is arranged to capacitively couple with the electrically conductive components in layers beneath it.
  • the shield 120 capacitively couples with these components in preference to the capacitive sensing electrode 110 coupling with these components.
  • the sensor pixel 100 is arranged to maintain the shield 120 at the reference voltage while a read-out signal is obtained from the read-out pixel.
  • the shield 120 will be at a known reference voltage.
  • the shield 120 is arranged to inhibit parasitic capacitive coupling between the capacitive sensing electrode 110 and any electrically conductive elements in layers beneath the shield 120.
  • the sensor may be arranged so that any parasitic capacitive coupling between the capacitive sensing electrode 110 and any other electrically conductive element in the sensor pixel 100 will be a coupling between the capacitive sensing electrode 110 and the shield 120.
  • the shield 120 is maintained at a fixed voltage while a read-out signal is being obtained from that sensor pixel, the contribution of the shield 120 to any parasitic capacitive coupling with the capacitive sensing electrode 110 may be known. Any influence that this coupling may have on the charge stored on the capacitive sensing electrode 110 during read-out may be factored into the resulting measurement. This influence may be determined as the shield 120 is at a known and fixed voltage.
  • the sensor pixel 100 may be arranged so that the shield 120 is the (primary) component of the sensor pixel 100 with which the capacitive sensing electrode 110 will couple.
  • Operation of the sensor pixel 100 of Fig. 2b may be the same as that of Fig. 2a.
  • either arrangement for the sensor pixels 100 may provide electrical shielding of the capacitive sensing electrode 110, and may thus improve a signal to noise ratio for the sensor.
  • the arrangement of Fig. 2a may advantageously require fewer electrically conductive layers, and capacitive coupling between the shield 120 and the capacitive sensing electrode 110 may be less substantial.
  • the arrangement of Fig. 2b may advantageously reduce constraints placed on the spatial layout for each individual electrically conductive layer.
  • Sensors of the present disclosure may comprise sensor pixels 100 of either or both types. Different examples of shields will now be described with reference to Figs. 3 to 5.
  • Fig. 3 shows a plan view of a portion of a sensor array 10 containing a plurality of sensor pixels 100.
  • the borders of the sensor pixels 100 are shown in dashed lines in Fig. 3.
  • the portion shown in Fig. 3 is intended to illustrate different relative arrangements for the shield 120 and capacitive sensing electrode 110 for one or more sensor pixels 100 of the sensor array 10.
  • Fig. 3 shows six examples of different configurations for shields 120 and capacitive sensing electrodes 110. Each example is intended to demonstrate possible different configurations for a shield, and one or more capacitive sensing electrodes to be shielded by that shield.
  • the sensor pixel 100 may be of the type shown in Fig. 2a.
  • the sensor pixel 100 is arranged with no spatial overlap between the first shield 120a and the first capacitive sensing electrode 110a.
  • the first shield 120a is arranged towards the periphery, e.g. towards the corner, of the sensor pixel.
  • the first shield 120a could alternatively be arranged so that it spans a larger area at the periphery of the sensor pixel 100. For example, it may span a strip along one or more sides (at the edge) of the sensor pixel, e.g.
  • the first capacitive sensing electrode 110a spans the majority of the remaining area of the sensor pixel 100 (and also the majority of the total area of the sensor pixel). Any electrically conductive components of the sensor pixel 100 may also be located in the area of the sensor pixel 100 underneath the first shield 120a.
  • the first shield 120a may be at least partially surrounded by a region containing no electrically conductive material. That region may separate the first shield 120a from the first capacitive sensing electrode 110a.
  • Fig. 3 shows one first shield 120a and one first capacitive sensing electrode 110a per one sensor pixel, but it will be appreciated that the first shield 120a may span across two or more sensor pixels 100 (i.e.
  • the first shield 120a may span only a subset of the area of each sensor pixel 100 to leave space for a first capacitive sensing electrode 110a for each sensor pixel 100 in the same electrically conductive layer.
  • each capacitive sensing electrode may be provided in an electrically conductive layer higher up in the pixel stack than the electrically conductive layer in which the shield is provided (i.e. with the capacitive sensing electrode above the shield).
  • each shield may include one or more openings therein for permitting electrical connection(s) between: (i) capacitive sensing electrode(s) in a layer above the shield, and (ii) electrical components in one or more layers beneath the shield.
  • one shield is shown per sensor pixel.
  • each shiel may instead span across two or more sensor pixels 100 (e.g. so that it provides the shield for multiple sensor pixels 100).
  • a second shield 120b is smaller than a second capacitive sensing electrode 110b.
  • the second shield 120b is shown in dashed lines, as it is in a layer beneath the second capacitive sensing electrode 110b. That is, an area covered by the second shield 120b is less than an area covered by the second capacitive sensing electrode 110b.
  • the area covered by the second shield 120b may be contained entirely within the area covered by the second capacitive sensing electrode 110b (as shown in Fig. 3). For example, the area covered by the second capacitive sensing electrode 110b may completely circumscribe and encompass the area covered by the second shield 120b.
  • the two areas may overlap, but with the area covered by the second shield 120b not completely falling within the area of the second capacitive sensing electrode 110b.
  • the area and location of the second shield 120b may be selected so that the second shield 120b overlies any electrically conductive elements in lower layers of the sensor pixel 100 (and thus so the portions of second capacitive sensing electrode 110b which do not overlie the second shield 120b also do not overlie any electrically conductive elements with which they may couple capacitively).
  • a third shield 120c is the same size as a third capacitive sensing electrode 110c (or at least the two areas may be substantially the same).
  • An area covered by the third shield 120c may be the same as the area covered by the third capacitive sensing electrode 110c, or the two areas may not fully overlap with each other.
  • a sixth shield 120f is larger than a sixth capacitive sensing electrode 110f.
  • the area covered by the sixth shield 120f may completely encompass the area covered by the sixth capacitive sensing electrode 110f.
  • one or more portions of the sixth capacitive sensing electrode 110f may not overlie the sixth shield 120f.
  • the sensor pixel 100 may be arranged so that such portions also do not overlie any electrically conductive elements of the sensor pixel 100 with which they may couple capacitively.
  • one shield spans across a plurality of sensor pixels 100.
  • a fourth shield 120d spans across a plurality of sensor pixels 100 and their associated fourth capacitive sensing electrodes 110d.
  • the fourth shield 120d is for every sensor pixel 100 in one row.
  • the fourth shield 120d may be arranged so that for each of the plurality of sensor pixels 100 it covers, the fourth capacitive sensing electrode 110d for that sensor pixel 100 will not have any regions which do not overlie the fourth shield 120d but do overlie electrically conductive elements in lower layers with which said electrode 110d may couple capacitively.
  • the fourth shield 120d may cover all, or a majority of, each of the fourth capacitive sensing electrodes 110d in the row.
  • an area covered by each of the fourth capacitive sensing electrodes 110d in the row may fall within the area covered by the fourth shield 120d.
  • one electrically conductive element may provide the shield for each of a plurality of sensor pixels 100, e.g. for every sensor pixel 100 in one row of the array 10.
  • a fifth shield 120e spans across a plurality of sensor pixels 100 and their associated fifth capacitive sensing electrodes 110e.
  • the fifth shield 120e may be the same as the fourth shield 120d, except that the fifth shield 120e spans across more than one row of sensor pixels 100.
  • the fifth shield 120e need not be for all of the sensor pixels 100 in each row.
  • the fifth shield 120e may be for every sensor pixel 100 in the array 10.
  • Such as shield may be arranged to inhibit parasitic coupling between each capacitive sensing electrode of the array 10 and any other electrically conductive elements within the array 10 with which each said capacitive sensing electrode may couple capacitively.
  • Fig. 4a shows a portion of an array 10 of sensor pixels 100.
  • Fig. 4a shows the array 10 without any shields 120 or shield connectors 122, but these are shown in Fig. 4b.
  • Two rows of sensor pixels 100 and three columns of sensor pixels 100 are shown in the array 10, but it will be appreciated that this is just a portion of the array 10, and that many more rows and columns may be provided.
  • a capacitive sensing electrode 110 is shown for each sensor pixel.
  • a plurality of electrically conductive lines are shown for the sensor array 10. These include: scan lines 131 , supply lines 132 and read-out lines 133. Black filled circles are used to show electrical connections between sensor pixels 100 and the relevant conductive lines.
  • Each sensor pixel 100 in the array 10 may be connected to a plurality of electrically conductive lines.
  • each sensor pixel 100 may be connected to a scan line 131 , a supply line 132 and a read-out line 133.
  • Each scan line 131 may be associated with a respective row of sensor pixels 100. That is, each scan line 131 is connected to all of the sensor pixels 100 in its row.
  • Each of the rows of sensor pixels 100 has an associated scan line 131.
  • Each supply line 132 may be associated with a respective column of sensor pixels 100. That is, each supply line 132 may be connected to all of the sensor pixels 100 in its column.
  • Each of the columns of sensor pixels 100 has an associated supply line 132.
  • Each read-out line 133 may be associated with a respective column of sensor pixels 100. That is, each read-out line 133 is connected to all of the sensor pixels 100 in its column.
  • Each of the columns of sensor pixels 100 has an associated scan line 131.
  • the sensor is configured to apply a scanning signal to a sensor pixel 100 (via the scan line 131 connected to that sensor pixel).
  • the scanning signal may be in the form of a voltage signal.
  • the sensor may be configured to selectively connect the scan line 131 to a voltage source in order to apply the scanning signal to the scan line 131.
  • the sensor may be configured to apply a scanning signal to every sensor pixel 100 in the row (which is connected to the scan line 131).
  • the sensor is configured to apply a supply signal to the sensor pixel 100 (via the supply line 132 connected to that sensor pixel). Applying the supply signal may comprise providing a supply voltage to the sensor pixel.
  • the sensor may be configured to selectively connect the supply line 132 to a supply voltage source in order to apply the supply voltage to the sensor pixel.
  • the sensor may be configured to apply the supply voltage to every sensor pixel 100 in a column.
  • An activated sensor pixel 100 may be a sensor pixel 100 which receives a scanning signal (from the scan line 131 to which it is connected) and to which a supply voltage is applied (from the supply line 132 to which it is connected).
  • the activated sensor pixel 100 is configured to output a read-out signal (to the read-out line 133 to which it is connected).
  • the read-out signal is indicative of the amount of charge stored on the capacitive sensing electrode 110. In turn, this may provide an indication of the proximity to the capacitive sensing electrode 110 of a conductive object to be sensed.
  • Each read-out line 133 may be connected to a processing channel of read-out processing circuitry configured to process read-out signals from that read-out line 133.
  • the sensor is configured to selectively apply scanning signals and the supply voltage to different sensor pixels 100 in order to selectively activate each said sensor pixels 100.
  • the sensor may be configured to apply a scanning signal to one scan line 131 at a time.
  • the scanning signal may charge that scan line 131 to a selected voltage (e.g. a voltage associated with a voltage source connected to that scan line 131).
  • the sensor may also be configured to apply a supply voltage to one or more of the supply lines 132.
  • Each of the sensor pixels 100 which are both: (i) in one of those supply lines 132, and (ii) in the row connected to said scan line 131 , will be activated. Read-out signals will be output from said sensor pixels 100 to the read-out lines 133 connected to those activated pixels 100.
  • the senor may be configured to apply a scanning signal (e.g. a fixed voltage) to all of the sensor pixels 100 in one row of the array 10 at a time.
  • the remaining rows of the sensor array 10 may not be activated. That is, they may not have their scan lines 131 charged to a scanning voltage. While one or more read-out signals are being obtained from any activated sensor pixels 100 in a row, the scan line 131 for that row will be at the scanning voltage.
  • the sensor pixels 100 within that row which output read-out signals may be only those which are connected to activated supply lines 132.
  • this arrangement may be used to selectively maintain sensor pixel shields 120 at the shielding voltage while read-out signals are obtained from capacitive sensing electrodes 110 associated with said shields 120.
  • Fig. 4b shows the same sensor array 10 as shown in Fig. 4a.
  • Fig. 4b also shows the sensor array 10 with shields 120 and shield connectors 122.
  • Each row of sensor pixels 100 has an associated shield 120. That is, one shield 120 is provided for all of the sensor pixels 100 in one row. A separate shield 120 is provided for each row of sensor pixels 100.
  • the shield 120 for each row is arranged to provide electrical shielding of the type described herein for all of the capacitive sensing electrodes 110 in its row. That is, for each row, every capacitive sensing electrode 110 in that row is shielded by the one shield 120 for that row.
  • the shield 120 for each row is connected to the scan line 131 associated with that row. As shown in Fig. 4b, a shield connector 122 may be provided for each shield 120, where said shield connector 122 electrically connects the shield 120 for one row to the scan line 131 for that row.
  • the sensor is arranged so that a voltage to be provided to the sensor pixels 100 in the row (e.g. the scanning voltage for activating at least one of those sensor pixels 100) will also be provided to the shield 120 for that row.
  • the sensor is arranged so that activating sensor pixels 100 in a row will also act to charge the shield 120 for that row to a selected voltage (i.e. to the scanning voltage).
  • sensor pixels 100 may not be activated without their shield 120 also being charged to a fixed (and known) voltage.
  • the shielding voltage used for the shield 120 will be the scanning voltage that is applied to the scan lines 131 for activating sensor pixels 100.
  • the sensor is configured so that, while a sensor pixel 100 is activated (i.e.
  • the selected voltage i.e. the scanning voltage
  • the sensor is configured to maintain the shield 120 at the selected voltage while a read-out signal is obtained from the activated sensor pixel.
  • the sensor addresses one row at a time. For a first row, the scanning signal is applied to the scan line 131 for that row, and a supply voltage is provided to some, or all, of the supply lines 132 for the different columns having pixels 100 in that row.
  • the activated pixels 100 in that row will receive both: (i) the scanning signal from its scan line 131 , and (ii) the supply voltage from its supply line 132.
  • Each activated pixel 100 will then output a read-out signal to its read-out line 133 for processing by read-out circuitry of the sensor.
  • this same scanning signal will also be applied to the shield 120 for that row.
  • the shield 120 will therefore be charged to the scanning voltage. There may be an initial period where a voltage of the shield 120 changes (i.e. increases or decreases) so that it is then at the scanning voltage. However, it will be appreciated that this will happen rapidly in practice. For the remaining duration of the time while the scanning signal is being applied to that scan line 131 (and thus while pixels 100 in that row may be activated to output read-out signals), the shield 120 will be maintained at the scanning voltage.
  • the shield 120 will be at a fixed voltage while the read-out signal is obtained indicative of an amount of charge stored on the capacitive sensing electrode 110. Any capacitive coupling occurring between the shield 120 and the capacitive sensing electrode 110 will therefore occur with one effective plate of this capacitor being held at a fixed, constant and known voltage (i.e. the scanning voltage). Therefore, any influence of this capacitive coupling may be known, as a voltage for one of the plates of the capacitor is already known, and the other plate provides the parameter to be measured (i.e. the amount of charge stored on that plate).
  • the shield 120 for shielding the capacitive sensing electrode 110 due to the arrangement of the shield 120 for shielding the capacitive sensing electrode 110, less parasitic capacitive coupling may occur between the capacitive sensing electrode 110 and other electrically conductive components of its sensor pixel.
  • the shield 120 by fixing the shield 120 to a known voltage, there may be fewer unknown sources of noise in the resulting measurements to be obtained from the sensor array 10.
  • the method may then continue by activating different sensor pixels 100 in the array 10.
  • the sensor may apply a scanning signal to a subsequent scan line 131.
  • the sensor may address sensor pixels 100 on a row-by-row basis.
  • sensor pixels 100 in a second row may be activated. This process may be repeated for every row in the sensor array 10. The process may be repeated several times for each row, so that each time a row is addressed, a first subset of the sensor pixels 100 in that row output read-out signals, and then the next time that row is addressed, a different subset of sensor pixels 100 in that row output read-out signals.
  • At least one read-out signal may be output and processed from each sensor pixel 100 in the array 10 (or at least for a large number, e.g. a majority) of the sensor pixels 100 in the array 10.
  • the shield 120 for those activated sensor pixels 100 will be being maintained at the scanning voltage (as the same scanning signal that activates those sensor pixels 100 will also be being applied to the shield 120 for those activated sensor pixels 100).
  • FIG. 5 Another example sensor array is shown in Fig. 5.
  • Fig. 5 shows a sensor array 10 containing a plurality of sensor pixels 100. The borders of the sensor pixels 100 are shown in dashed lines. Fig. 5 also shows a capacitive sensing electrode 110 for each sensor pixel 100 and a shield 120. In the example of Fig. 5, the shield 120 covers the entire sensor array 10. In other words, each sensor pixel 100 has its shield 120 provided for by the same single electrically conductive element.
  • the interference protection circuitry 140 may comprise a plurality of diodes for connecting the shield 120 to voltage rails of the sensor.
  • Inset A of Fig. 5 shows the interference protection circuitry 140 with a first (e.g. high) voltage rail 141 and a second (e.g. low) voltage rail 142.
  • the circuitry shown in Inset A also includes a high diode 141a and a low diode 142a.
  • the shield 120 spans across the entire sensor array 10 so that it provides electrically shielding for every capacitive sensing electrode 110 in the array 10.
  • the shield 120 may be provided by an electrically conductive layer which covers the entire (or at least the majority of the) area of the sensor array 10.
  • the sensor of Fig. 5 may be configured to operate in the same way to the sensors described above, e.g. in that sensor pixels 100 may be activated by receiving scanning signals on their scan line and a supply voltage on their supply line. In Fig. 5, one connection is shown between the shield 120 and the voltage source 124. However, there may be a plurality of such connections.
  • the voltage source 124 may be a controlled voltage source, e.g. a voltage source which is configured to set the shield 120 to a selected voltage.
  • the controlled voltage source 124 is configured to control a voltage of the shield 120 so that the selected voltage (i.e. the shielding voltage) is a constant voltage while read-out signals are obtained from activated pixels 100.
  • the voltage source 124 could be provided by another voltage source used within the sensor, such as a voltage source for scanning signals or a supply voltage source.
  • the voltage source 124 may be an electrical ground, e.g. so that the connection of the shield 120 to the electrical ground grounds any voltage thereof (e.g. to 0 V).
  • the voltage source 124 may be a separate voltage source. For example, it may be a voltage source specifically for the shield 120.
  • the shield 120 may have a plurality of different electrical connections to the voltage source 124. For example, there may be an electrical connection (e.g. direct or indirect) between the shield 120 and the scanning voltage source such that any time a scanning voltage is to be applied to any of the rows in the sensor array 10, that scanning voltage is also provided to the shield 120 via said electrical connection.
  • an electrical connection e.g. direct or indirect
  • the shield 120 may be connected to every supply line in the sensor array 10.
  • the shield 120 may only be connected to some of the supply lines, but where those supply lines are selected so that the shield 120 will receive a supply voltage for every activated pixel.
  • multiple supply lines may be activated at any one time, and so the shield 120 may only need to be connected to some of the supply lines to be always receiving the supply voltage when sensor pixels 100 are activated.
  • there may be a direct electrical connection between the shield 120 and the supply voltage source such that any time a supply voltage is to be applied to any of the columns in the sensor array 10, that supply voltage is also provided to the shield 120 via said direct connection.
  • the senor is arranged so that the shield 120 will be maintained at its shielding voltage while read-out signals are obtained from activated sensor pixels 100 within the array 10. It will be appreciated that, as the shield 120 covers all of the capacitive sensing electrodes 110 of the sensor array 10, any subset of sensor pixels 100 within the array 10 could be activated at any one time and the single shield 120 would still be providing electrical shielding for those sensor pixels 100.
  • the sensor may operate by activating sensor pixels 100 in a first row, then activating sensor pixels 100 in a subsequent row, and so on until read-out signals have been obtained from a desired number/proportion of the sensor pixels 100 in the array 10. For example, the process may be repeated iteratively until a read-out signal has been obtained from every sensor pixel. Each time a read-out signal is being obtained from an activated sensor pixel, the shield 120 will be maintained at its shielding voltage. It will be appreciated in the context of the present disclosure that each subsequent activation of sensor pixels 100 may occur very quickly, e.g. so that read-out signals are obtained from all of the sensor pixels 100 in a relatively short time period.
  • One advantage of using a single shield 120 for all of the sensor pixels 100 in the array 10 is that there may be less need for charging/discharging the shield 120 to the shielding voltage between subsequent sensor pixel activations. For example, as one sensor pixel activation is finishing, the shield 120 will be at the shielding voltage, and the next sensor pixel activation will occur very shortly thereafter, and so a shield voltage is unlikely to have changed significantly between one sensor pixel activation ending and the next sensor pixel activation beginning. This may reduce overall power consumption needed to provide the sensor.
  • one or more shields 120 are included to provide electrical shielding of the capacitive sensing electrode(s) 110 from parasitic coupling with other elements of the sensor, such as other electrically conductive components within the sensor (e.g. electrical components of the sensor pixel 100 and/or lines for providing electrical connections with the sensor pixel). Shields of the present disclosure may be provided with additional properties for facilitating improved operation of the sensor. Although the following examples will predominantly be described with reference to the shield 120 of Fig. 5, it will be appreciated that they could also apply to any of the shields 120 disclosed herein.
  • the shield 120 may be arranged to provide interference protection.
  • the shield 120 may be arranged to provide protection from undesirable electrical effects, such as electrostatic discharge and/or electromagnetic interference.
  • the sensor may also include interference protection circuitry 140 of the type shown in Fig. 5.
  • the interference circuitry is configured to selectively provide electrical conduction paths away from the shield 120 for excursions beyond a threshold level. For example, if a voltage of the shield 120 is greater than an upper threshold voltage or lower than a lower threshold voltage (e.g. a negative threshold voltage), then the protection circuitry 140 is configured to divert away excess current from the shield 120.
  • the interference protection circuitry 140 may be formed of one or more diodes which connect the shield 120 to the first (e.g. high) voltage rail 141 and one or more diodes which connect the shield 120 to the second (e.g. low) voltage rail 142.
  • One high diode 141a and one low diode 142a are shown, but two or more may be provided.
  • the shield 120 is connected to the high voltage rail 141 via the high diode 141a.
  • the high diode 141a is shown in Inset A as a shorted transistor.
  • the shield 120 is connected to the low voltage rail 142 via the low diode 142a, and the low diode 142a is shown as a shorted transistor.
  • the Interference protection circuitry 140 is arranged to provide electrical conduction paths away from the shield 120.
  • the high diode 141a is arranged to provide a conduction path between the shield 120 and the high voltage rail 141. In the event that a voltage of the shield 120 exceeds a threshold voltage (e.g. in the event that the shield voltage is greater than a voltage of the high rail), current may flow away from the shield 120 and through the high diode 141a to the high voltage rail 141.
  • the low diode 142a is arranged to provide a conduction path between the low voltage rail 142 and the shield 120 for diverting current to inhibit a voltage of the shield 120 being below a threshold voltage (e.g. if the voltage of the shield 120 is too negative).
  • the senor may be configured to utilise the shield 120 and the interference protection circuitry 140 to provide electrical protection for the sensor, and any electrical components thereof.
  • the sensor may be configured to utilise the shield 120 and the interference protection circuitry 140 to provide shielding of the sensor from electrostatic discharge and/or electromagnetic interference.
  • the shield 120 may be provided by an opaque material.
  • an electrically conductive, but non-transparent, metal may be used.
  • the shield 120 may be arranged to provide optical shielding for components beneath it.
  • the shield(s) 120 of the sensor may be arranged to overlie these components, and in particular to overlie the channel regions of the TFTs.
  • this may also improve operating characteristics of the TFTs if the shield 120 is opaque (e.g. opaque to visible light). For example, certain performance characteristics may be influenced by incident optical light rays on the TFT.
  • the shield(s) 120 may provide optical protection for the sensor, e.g. for protecting components beneath the shield 120 from incident light.
  • This incident light may be visible light and/or ultraviolet light (and/or electromagnetic radiation in other parts of the EM spectrum).
  • the shield 120 may be arranged to facilitate touch sensitive operation. For example, touch sensing may be detected using the shield 120. This may be of particular utility when the shield(s) 120 cover larger areas of the sensor array 10 (e.g. when they cover multiple sensor pixels 100), such as when they cover the entire array 10 or when they cover each row/column.
  • the capacitive sensing electrodes 110 may be provided at a sufficiently high spatial resolution to facilitate biometric scanning, e.g. to enable sufficiently high spatial resolution data to be obtained for the object contacting the sensor to enable biometric identification therefrom, such as based on obtained fingerprint data.
  • the sensor may be configured to also operate in a touch sensitive mode. In the touch sensitive mode, the sensor may be configured to identify that an object is interacting with, e.g.
  • the sensor may be configured to use the shield(s) 120 of the sensor array 10.
  • use of the shield(s) 120 of the sensor to detect contact may be as an alternative to, or in addition to, using the capacitive sensing electrode(s) 110 for this purpose.
  • the sensor may be configured to operate in two different modes: (i) a first mode in which the shield 120 is used for capacitive sensing, and (ii) a second mode in which the capacitive sensing electrodes 110 are used for capacitive sensing.
  • the first mode may be used for contact sensing (e.g. to detect an indication of contact from an object with the sensor).
  • the second mode may be used for capacitive biometric skin contact sensing.
  • the sensor may be configured to operate initially in the first mode until an indication of contact is sensed, and then to switch into operation into the second mode.
  • the controller may be configured to sense contact in the first mode, and in the event that an indication of contact is sensed, to switch into the second mode to perform higher spatial resolution sensing (e.g. to perform capacitive biometric skin contact sensing of the object contacting the sensor).
  • a shield 120 to inhibit capacitive coupling between the capacitive sensing electrode 110 and electrically conductive components of the sensor (such as the electrically conductive component 102).
  • the shield 120 is arranged to provide preferential capacitive coupling for the parasitic capacitances.
  • any capacitive coupling from components of the sensor pixel 100 may be between those components and the shield 120 in preference to coupling between those components and the capacitive sensing electrode 110.
  • the shield 120 may not completely eradicate all parasitic capacitive coupling with the capacitive sensing electrode 110. Some parasitic coupling with the capacitive sensing electrode 110 may still exist, but the shield 120 is arranged to try to minimise an amount of this coupling which remains.
  • parasitic coupling with the electrically conductive component 102 there may be a plurality of different sources of capacitive coupling, e.g. including one or more TFTs, conductive lines, capacitors etc. which provide the sensor pixels 100 and which span across the sensor array 10.
  • the shield(s) 120 are arranged to minimise an amount of parasitic coupling with the capacitive sensing electrode 110 from any potential sources of parasitic coupling.
  • the sensor may be arranged so that the shield 120 preferentially couples capacitively with all of these sources of parasitics, e.g. the shield 120 may overlie all of these components.
  • each sensor pixel 100 may comprise a sensor element (instead of the capacitive sensing electrode 110), such as an optical sensor detector, and the sensor may be configured to provide shielding of said sensor element from other components of the sensor.
  • the shielding voltage may be any suitable voltage.
  • the shield 120 is an ‘active shield’ in the sense that, when shielding the capacitive sensing electrode 110, the shield 120 will be actively connected to a suitable component for maintaining the shield 120 at the shielding voltage (e.g. the shield 120 will not just be floating).
  • the shield voltage could be a positive voltage or it could be zero.
  • the shield 120 may be connected to one or more electrically conductive lines of the sensor array 10 in order to set the shield 120 to its fixed shielding voltage. For example, where the shielding voltage is positive, the shield 120 may be connected to a positive voltage source (such as a scan line or a supply line) and where the shielding voltage is zero, the shield 120 may be connected to a ground voltage (e.g.
  • the shield 120 could instead be connected to a separate voltage source, or other suitable voltage source for maintaining the shield 120 at the shielding voltage.
  • the shield 120 may be connected to a plurality of conductive lines, such as a plurality of scan and/or supply lines.
  • the shield 120 may be permanently maintained at the shielding voltage (e.g. rather than being selectively connected to a reference voltage source when sensor pixels 100 are activated).
  • one shield 120 may be provided for each row of sensor pixels 100.
  • a shield 120 could alternatively be provided for each column of sensor pixels 100, e.g. and where each shield 120 is connected to the supply line for its column so that the shield 120 will be charged to the supply voltage for shielding.
  • each of the examples described herein may be implemented in a variety of different ways. Any feature of any aspects of the disclosure may be combined with any of the other aspects of the disclosure. For example, method aspects may be combined with apparatus aspects, and features described with reference to the operation of particular elements of apparatus may be provided in methods which do not use those particular types of apparatus.
  • each of the features of each of the examples is intended to be separable from the features which it is described in combination with, unless it is expressly stated that some other feature is essential to its operation.
  • Each of these separable features may of course be combined with any of the other features of the examples in which it is described, or with any of the other features or combination of features of any of the other examples described herein.
  • equivalents and modifications not described above may also be employed without departing from the invention.

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Abstract

Un capteur capacitif comprend un réseau de pixels de capteur, chaque pixel de capteur comprenant : une électrode de détection capacitive ; et un blindage. Le blindage est électriquement conducteur et conçu pour protéger électriquement l'électrode de détection capacitive d'un couplage parasite avec d'autres éléments du capteur. Le capteur est conçu pour maintenir le blindage à une tension de blindage tandis qu'un signal de lecture est obtenu à partir du pixel de capteur.
PCT/GB2024/050685 2023-03-14 2024-03-14 Capteur et procédé Pending WO2024189360A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB2303709.6 2023-03-14
GB2303709.6A GB2628120A (en) 2023-03-14 2023-03-14 Sensor and method

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WO2024189360A1 true WO2024189360A1 (fr) 2024-09-19

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TW (1) TW202441360A (fr)
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Citations (9)

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