Sensors and methods

Abstract

A capacitive sensor comprising an array of multiple sensor pixels, each sensor pixel comprising a capacitive sensing electrode and a shield. The shield is conductive and is positioned 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 shield voltage while a readout signal is being acquired from the sensor pixels.

Description

Technical Field

[0001] This disclosure relates to the field of sensors and sensing methods. In particular, this disclosure relates to the field of capacitive sensors such as capacitive touch sensors and methods of operating the same sensors.

Background Art

[0002] International Publication Nos. WO 2020 / 178605 and WO 2022 / 043699 disclose capacitive biometric skin contact sensors in different examples. These sensors are operable to obtain capacitance measurements for a sensor array over a large area. Based on these capacitance values, biometric data may be obtained for a user contacting the sensor. For example, the ridges and valleys and differences in the user's skin contours may be identified based on differences in capacitance measured across the sensor array. The sensor may implement biometric authentication by comparing the obtained distribution of skin contours to a known distribution of skin contours. For example, the sensor may be a fingerprint sensor that may identify a user based on the user's fingerprint. For both of the prior art disclosures, the particular sensor pixel designs disclosed herein are selected to provide a high signal-to-noise ratio for measurements obtained using the same sensor pixels.

[0003] This disclosure aims to provide improvements over the prior art sensors.

Summary of the Invention

[0004] Aspects of the present disclosure are set forth in the independent claims, and optional features are set forth in the dependent claims. Aspects of the present disclosure may be provided in relation to each other, and features of one aspect may be applied to other aspects.

[0005] In one embodiment, a capacitive sensor is provided comprising an array of multiple sensor pixels, each sensor pixel comprising a capacitive sensing electrode and a shield. The shield is conductive and is 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 shield voltage while a readout signal is acquired from the sensor pixels.

[0006] The sensor is configured to maintain the shield at a shield voltage, thereby creating parasitic capacitive coupling between the shield and the capacitive sensing electrode, and the active capacitor is maintained at a known voltage. That is, the shield is maintained at the shield voltage. The other side of the active capacitor (the capacitive sensing electrode) stores a charge amount indicating the proximity of the conductive object being detected to that electrode. The amount of charge stored on the capacitive sensing electrode may also be affected by the capacitive coupling of the capacitive sensing electrode with the shield. By fixing the shield to a constant voltage, the parasitic coupling between the capacitive sensing electrode and the shield may be a known amount. Then, 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. For example, since the readout signal indicates a specific amount of charge stored on the capacitive sensing electrode, the sensor may determine what the contribution of the capacitive coupling to that amount of charge is. This may then allow for a better determination of the contribution of the proximity of the conductive object being detected to the amount of charge stored on the capacitive sensing electrode.

[0007] Embodiments may enable a significant increase in the signal-to-noise ratio, which may be obtained from the readout signals from the array of sensor pixels. This may also enable the provision of a larger dynamic range for measurements obtained using the sensor. In other words, contributions to the readout signals from unknown and / or unquantifiable noise sources are reduced for each given readout signal. Instead, the signal noise associated with the capacitive coupling between the capacitive sensing electrode and the shield is a known amount that may be compensated for. Thus, this mechanism may increase the signal-to-noise ratio for measurements obtained from the sensor. A larger response within each readout signal to changes in charge stored in the capacitive sensing electrode may be derived from the readout signals obtained, and therefore a larger dynamic range may also be obtained from the sensor.

[0008] The shield voltage may be a constant voltage, such as a DC voltage. Maintaining the shield at the shield voltage while a readout signal is being acquired from the sensor pixel may involve operating the sensor so that the shield is connected to a voltage source while the readout signal is being acquired. The voltage source may be a DC voltage source. This voltage source may also be used to supply voltage to other components of the sensor array, and may be a separate voltage source for the shield, or may be electrical ground. The sensor may be configured to activate a sensor pixel that outputs a readout signal and at the same time connect the shield for that sensor pixel to a shield reference voltage source. For example, the sensor may be configured to apply one or more electrical signals to activate a sensor pixel, and the application of these electrical signals also functions to maintain the shield at the shield voltage. For example, the sensor may be configured to electrically connect the shield to a shield voltage source so that the shield voltage source charges / discharges / neither the shield to the shield voltage and then maintains the shield at the shield voltage while a readout signal is being acquired from the sensor pixel.

[0009] The sensor may have multiple conductive lines across the array. The shield may be connected to at least one of these conductive lines. At least one conductive line may electrically connect the shield to a control voltage source. For example, at least one conductive line may connect the shield to a DC voltage. For example, the control voltage source may be configured to control the shield to a selected voltage (e.g., a fixed constant voltage) when electrically connected to the shield. At least one conductive line may include (i) one or more scanning lines, (ii) one or more ground lines, or (iii) one or more voltage supply lines.

[0010] The shield may overlap other elements of the sensor. For example, the other elements may be located below (e.g., below the shield vertically). The top surface of the sensor may be the contact surface to which the detected object comes into contact. 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 other elements of the sensor. The capacitive sensing electrode may overlap the shield. For example, the shield may vertically isolate the capacitive sensing electrode from other elements of the sensor.

[0011] A single electrically conductive element may provide shielding for multiple sensor pixels. A single electrically conductive element may provide shielding for all sensor pixels in an array; for example, a sensor array may have one shield that electrically shields all capacitive sensing electrodes in the array. A single electrically conductive element may be connected to multiple conductive lines across a sensor array. A single electrically conductive element may provide shielding for all sensor pixels in a row, and the shield may be connected to a scanning line for the row.

[0012] The sensor may be a capacitive touch sensor. Each readout signal may indicate the amount of charge stored in the capacitive sensing electrode. Each readout signal may provide an indication of the proximity of the object being detected to the capacitive sensing electrode. For example, 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 detection. When operating in the first mode, the sensor may be configured to switch operation to a second mode in which the capacitive sensing electrode is used to perform capacitive biometric skin contact detection, depending on the acquisition of an indication of contact. The shield for each sensor pixel may be substantially opaque to visible light and / or ultraviolet light. The shield for each sensor pixel may be arranged to provide shielding from electromagnetic interference and / or electrostatic interference. The shield may be coupled to high-voltage and low-voltage rails, respectively, via one or more diodes arranged to provide protection from electrical interference. The sensor pixel circuit may include at least one thin-film transistor TFT. The shield may be arranged to electrically shield the capacitive sensing electrode from parasitic coupling with the TFT. The TFTs of this disclosure may include at least one of the following types of TFTs: (i) oxides such as indium gallium zinc oxide ("IGZO"), (ii) amorphous silicon ("aSi"), (iii) (low temperature) polysilicon ("LTPS" / "pSi"), (iv) combinations of LTPS and oxides such as LTPO, and (v) organic materials.

[0013] The sensor may comprise an array of sensor pixels, each of which comprises one or more thin-film transistors ("TFTs") and a capacitive sensing electrode. The sensor pixels may be arranged in an active matrix array, and the sensor may be operable to process each pixel by applying a scanning signal to each pixel. Each pixel being processed may also receive a supply voltage from a supply line. Each pixel being processed may output a readout signal to a readout line. For each sensor pixel, the readout signal may indicate the proximity of a conductive material to be detected to the capacitive sensing electrode of that sensor pixel. The sensor may comprise a readout circuit configured to process the readout signal.

[0014] For example, each sensor pixel may include at least one TFT that controls the readout signal from that sensor. This may include a “sensing TFT” positioned to output the readout signal to a readout line. When each pixel is processed by a scan signal (along the scan line connected to that pixel) and receives a supply voltage (from the supply line connected to that pixel), the sensing TFT may output a readout signal to the readout line to which the sensing TFT is connected. A capacitive sensing electrode may be coupled to the gate region of the sensing TFT, and the magnitude of the readout signal from the sensing TFT to the readout line may be influenced by the effective capacitance of the capacitive sensing electrode (i.e., the magnitude may indicate the proximity of the detected conductive material to the capacitive sensing electrode). The sensor may be configured to repeat this process for different sensor pixels so that a readout signal is acquired for each sensor pixel in the array.

[0015] In one embodiment, a capacitive sensing method is provided that uses an array of multiple sensor pixels, each of which comprises (i) a capacitive sensing electrode and (ii) a shield, the shield being conductive and arranged to electrically shield the capacitive sensing electrode from parasitic coupling with other elements of the sensor. The method includes maintaining the shield at a shielding voltage while a readout signal is being acquired from the sensor pixel in order to provide the same electrical shielding of the capacitive sensing electrode.

[0016] The shield may be connected to a control voltage source to maintain the shield at a shield voltage. The shield may be connected to the control voltage source by one or more conducted lines across the sensor array. The shield may be connected to a control voltage source to maintain the shield at a shield voltage while readout signals are being acquired from the sensor pixels by (i) one or more scanning lines, (ii) one or more ground lines, or (iii) one or more voltage supply lines. The method may include using the shield to acquire an indication of contact with the sensor array, and then using a capacitive sensing electrode to perform a biometric detection after the indication of contact has been detected. The method may include simultaneously maintaining the shields of multiple sensor pixels at a shield voltage.

[0017] Aspects of this disclosure may include one or more computer program products comprising computer program instructions configured to control a capacitive biometric skin-contact sensor in order to perform any of the methods disclosed herein. [Brief explanation of the drawing]

[0018] Some examples of this disclosure are described hereby for illustrative purposes only, with reference to the figures.

[0019] [Figure 1] Figure 1 is a schematic diagram showing the array of sensor pixels for a capacitive sensor. [Figure 2a] Figure 2a is a schematic diagram showing a cross-sectional view of a sensor pixel. [Figure 2b] FIG. 2b is a schematic view showing a cross-sectional view of a sensor pixel. [Figure 3] FIG. 3 is a schematic view showing an array of sensor pixels for a capacitive sensor. [Figure 4a] FIG. 4a is a schematic view showing an array of sensor pixels for a capacitive sensor. [Figure 4b] FIG. 4b is a schematic view showing an array of sensor pixels for a capacitive sensor. [Figure 5] FIG. 5 is a schematic view showing an array of sensor pixels for a capacitive sensor.

[0020] In the drawings, like reference numerals are used to indicate like elements.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The present disclosure relates to the use of an active shield for a capacitive sensor pixel. The shield is arranged to prevent capacitive coupling of the capacitive sensor electrodes in the sensor pixel to other nearby elements of the sensor, such as other electrically conductive components of the sensor pixel itself. Instead, the shield is arranged to capacitively couple to other electrically conductive elements of the sensor. While a readout signal is being acquired from the sensor pixel, the shield is maintained at a fixed known voltage. During this period, the shield voltage is known and fixed, and the shield prevents capacitive coupling of the capacitive sensing electrode, which has an unknown voltage, to other electrically conductive elements, so that the value for any capacitive coupling between the capacitive sensing electrode and the shield may be accurately determined. Thus, this may reduce the amount of noise present in the readout signal indicative of the charge stored on the capacitive sensing electrode of the sensor pixel.

[0022] An exemplary sensor pixel design is described in relation to FIGS. 2a and 2b, but first, an exemplary sensor array is described with reference to FIG. 1.

[0023] FIG. 1 shows a plan view of a part of a sensor array 10 including a plurality of sensor pixels 100. Each sensor pixel 100 is shown as having a capacitive sensing electrode 110. For simplicity, other components of the sensor array 10 including the components in each sensor pixel 100 are not shown in FIG. 1.

[0024] The sensor array 10 includes 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 in 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 occupy most of the area of the sensor pixel 100 of the capacitive sensing electrode 110 (when viewed in plan). By increasing the area covered by the capacitive sensing electrode 110, a larger amount of charge may be stored in the same electrode 110. The area covered by each individual electrode 110 may also be limited such that the spatial resolution of the capacitive sensor is high enough to provide biometric sensing (e.g., to identify the contour of the user's skin).

[0025] Each sensor pixel 100 is configured to output a readout signal indicating the amount of charge stored in the capacitive sensing electrode 110 of that sensor pixel 100. This may then provide an indication of the proximity of the conductive object being detected to the capacitive sensing electrode 110. The sensor array 10 may comprise an active matrix array of sensor pixels 100. Each sensor pixel 100 may be selectively activated so that a readout signal is obtained from that sensor pixel 100. The sensor may be configured to activate multiple different sensor pixels 100 at once. For example, the sensor may be configured to activate each sensor pixel 100 in a row at once. Readout signals may then be obtained from the sensor pixels 100 in the row. For example, readout signals may be obtained from some or all of the sensor pixels 100 in the row.

[0026] Each sensor pixel 100 may include one or more electrical elements configured to output a readout signal indicating the amount of charge stored in the capacitive sensing electrode 110. The readout signal may also be an electrical signal such as a current signal or a voltage signal. For example, the readout signal may be in the form of a current signal, where, for example, the magnitude of the current of the 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 include other types of electrical elements such as capacitors. The sensor array 10 may also include a plurality of electrically conductive lines connected to the sensor pixels 100 that activate the sensor pixels 100 and transmit readout signals from the sensor pixels 100 to the sensor readout circuit.

[0027] Each sensor pixel 100 may comprise a multilayer pixel stack. The pixel stack for each sensor pixel 100 may comprise multiple conductive layers (e.g., metallization layers). Different electrical elements may be provided across the multiple conductive layers. Each conductive layer may be isolated from adjacent conductive layers by an intervening layer. The intervening layer may include an insulating material. The stack may also include a semiconductor material providing one or more TFTs in the stack. The top surface of the sensor may be positioned so as to be in contact with the object to be detected. The capacitive sensing electrode 110 for each sensor pixel 100 may be provided in the top conductive layer of the stack (e.g., so that there is no intervening conductive layer between the capacitive sensing electrode 110 and the object to be detected). Other conductive components in the stack may be provided in one or more conductive layers below the top conductive layer (e.g., in the layers below the capacitive sensing electrode 110).

[0028] The sensor of this disclosure includes a shield arranged to electrically shield the capacitive sensing electrode 110 from parasitic coupling with other elements of the sensor. In particular, the shield may electrically shield the capacitive sensing electrode 110 of a sensor pixel 100 from other components within the sensor pixel (e.g., one or more transistors and / or capacitors). In this regard, the shield may be arranged so as to capacitively couple with the sensor element itself. The sensor is configured to maintain the shield at a shield voltage such that any capacitive coupling between the capacitive sensing electrode 110 and the shield occurs with the shield at a known reference voltage. Thus, the effect of the shield on this capacitive coupling is known (because the reference voltage for the shield is known), whereas, if the capacitive coupling relates to other components of the sensor, the effect of the second effective plate of the capacitor is not known because the amount of charge stored in that component may change.

[0029] Here, examples of different sensor pixel mechanisms including the shield are described with reference to Figures 2a and 2b. With reference to Figure 2a, the sensor pixel is positioned such that the capacitive sensing electrode 110 is laterally offset from any electrical element that the capacitive sensing electrode 110 may capacitively couple with, and the component is laterally aligned with the shield. With reference to Figure 2b, the sensor pixel is positioned such that the shield is in an intervening layer between the capacitive sensing electrode 110 and the component.

[0030] Figure 2a shows a cross-sectional view of the sensor pixel 100. The sensor pixel stack for the sensor pixel 100 is shown as comprising two electrically conductive layers, namely a first electrically conductive layer 105a and a second electrically conductive layer 105b. For simplicity, other electrically conductive layers and any intervening layers are not shown. The sensor pixel 100 includes a substrate 101, an electrically conductive component 102, a capacitive sensing electrode 110, and a shield 120. A shield connector 122 is also shown. Although not explicitly shown in Figure 2a, the shield connector 122 is connected to one or more electrically conductive components, for example, a reference voltage source (therefore, for example, to electrically connect the shield 120 to the component to maintain the shield at the shield voltage).

[0031] The substrate 101 provides a base layer for the sensor pixels, and the remaining layers of the stack are provided on top of this base layer. The first electrically conductive layer 105a is a layer below the second electrically conductive layer 105b. The electrically conductive components 102 are provided at least partially in the first electrically conductive layer 105a. The first electrically conductive layer 105a may comprise a metallization layer. For example, the first electrically conductive layer 105a may be formed in an area of ​​electrically conductive material, such as metal, deposited on the layer below the first electrically conductive layer 105a, for example, on the substrate 101 itself.

[0032] The sensor pixel 100 may be arranged such that the electrically conductive component 102 (and any other electrically conductive components not shown) is 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. For example, the first area may occupy less than half of the total area of ​​the sensor pixel. The electrically conductive component 102 may comprise a TFT. In practice, the TFT may be provided using two or more electrically conductive layers, and for simplicity it should be understood that this is only shown as one component in one electrically conductive layer. The electrically conductive component 102 may be located towards the periphery of the sensor pixel. For example, the electrically conductive component 102 may be located around the sensor pixel 100 (e.g., on the outer edge) closer to the center of the sensor pixel.

[0033] The shield 120 and the capacitive sensing electrode 110 are provided in the second electrically conductive layer 105b, which is above the first electrically conductive layer 105a. Although not shown, one or more layers, such as an intervening insulating layer, may be present between the first electrically conductive layer 105a and the second electrically conductive layer 105b. The shield 120 and the capacitive sensing electrode 110 are isolated from each other in the second electrically conductive layer 105b (for example, the shield 120 and the capacitive sensing electrode 110 do not come into contact). The shield 120 may occupy a smaller area in the second electrically conductive layer 105b than the capacitive sensing electrode 110. For example, the capacitive sensing electrode 110 may occupy most of the area of ​​the second electrically conductive layer 105b. The second electrically conductive layer 105b may include a metallization layer. For example, the second electrically conductive layer 105b may be formed on the layer below the second electrically conductive layer 105b, for example, in an area of ​​an electrically conductive material such as a metal deposited on an insulating layer.

[0034] The shield 120 overlaps the electrically conductive component 102; that is, the shield 120 is positioned above the electrically conductive component 102. One or more layers may exist between the shield 120 and the electrically conductive component 102. The shield 120 may cover the entire (or at least a large portion of) the first area. In other words, the electrically conductive component 102 may be completely covered by the shield 120. For example, when viewed in plan, the area occupied by the electrically conductive component 102 may be completely within the area occupied by the shield 120. Although only one electrically conductive component 102 is shown in Figure 2a, in examples where multiple electrically conductive components exist, it will be understood that they may all be covered by the shield 120 (for example, multiple identical electrically conductive components may all be within the area covered by the shield 120). The capacitive sensing electrode 110 does not overlap the electrically conductive component 102. For example, the electrically conductive components do not have to be located beneath the capacitive sensing electrode 110, or at least only electrically conductive components such that any capacitive coupling between the electrically conductive components and the capacitive sensing electrode 110 can be ignored may be located beneath the capacitive sensing electrode 110.

[0035] The shield 120 is positioned vertically above the conductive component 102 (for example, when the sensor is positioned vertically with the second conductive layer 105b above the first conductive layer 105a). The shield 120 may completely encompass the lateral range of the conductive component 102. The capacitive sensing electrode 110 may be offset laterally from the conductive component 102. Lateral overlap is not required between the capacitive sensing electrode 110 and the conductive component 102. For example, the conductive component is not required to be vertically below the capacitive sensing electrode 110.

[0036] It will be understood that one or more conductive connections may be provided to electrically connect components in the second conductive layer 105b to components in the first conductive layer 105a. For example, each sensor pixel 100 may include one or more conductive vias that provide electrical connections between different conductive layers. Only one of these, a shield connector 122, is shown in Figure 2a. Not shown in Figure 2a, the shield connector 122 electrically connects the shield 120 to one or more other conductive components of the sensor in order to allow the shield 120 to be maintained at a shield voltage. For example, the shield connector 122 electrically connects the shield 120 to a reference voltage source. In Figure 2a, the shield connector 122 is shown as connecting away from the sensor pixel 100 (on the substrate 101) to provide this connection to the reference voltage source (the reference voltage source is not shown in Figure 2a). Any suitable electrical connection may be used to enable the shield 120 to be connected to a reference voltage source (and thus to maintain the shield 120 at the reference voltage).

[0037] The sensor pixel 100 is arranged to output a readout signal indicating the amount of charge stored in the capacitive sensing electrode 110. In this regard, the electrically conductive component 102 is configured to output a readout signal indicating the amount of charge stored in the capacitive sensing electrode 110. The sensor may be configured to provide one or more electrical signals to the sensor pixel 100 in order for the sensor pixel 100 to output a readout signal. For example, the sensor may apply a scanning signal to the sensor pixel 100 and / or provide a supply voltage to the sensor pixel. Accordingly, the sensor pixel 100 may be configured to output a readout signal.

[0038] The sensor is configured to maintain the shield 120 at a reference voltage. The shield connector 122 is positioned to electrically connect the shield 120 to the reference voltage source. Thus, the shield 120 may be maintained at a reference voltage associated with the reference voltage source. The sensor may be configured to selectively maintain the shield 120 at a reference voltage. For example, the sensor may selectively connect the shield 120 to the reference voltage source. The sensor is configured such that the shield 120 is connected to the reference voltage source while the sensor pixel 100 is operating to provide a readout signal from the sensor pixel 100.

[0039] The shield 120 is positioned to capacitively couple with the electrically conductive component 102. In other words, the shield 120 and the electrically conductive component 102 may be positioned effectively to provide one plate of a capacitor (for example, here the two plates are separated by an optional intervening layer such as an insulating layer). In the context of this disclosure, it will be understood that the shield 120 may be positioned to capacitively couple with any suitable component (e.g., any part of the sensor pixel 100 which may store a certain charge and provide capacitive coupling). For simplicity, this is shown as the electrically conductive component 102, but the component may have further or alternative electrical properties. The shield 120 is maintained at a reference voltage of the shield 120, so that the plates of the active capacitor are at a known reference voltage. Since the shield 120 is maintained at a reference voltage while a readout signal is acquired from the sensor pixel, the voltage of the shield 120 during that period may be known.

[0040] The capacitive sensing electrode 110 is positioned away from the electrically conductive component 102 such that no (or minimal) capacitive coupling occurs between the two. Instead, the capacitive coupling is between the shield 120 and the electrically conductive element. In other words, the sensor is positioned to produce a controlled (parasitic) capacitive coupling between the shield 120 and the electrically conductive component 102. This controlled capacitive coupling with respect to the shield 120 is selected to prevent parasitic capacitive coupling between the capacitive sensing electrode 110 and the electrically conductive component 102 (or any other relevant component, which may be a fluctuating unknown voltage and therefore provide an unknown parasitic effect).

[0041] During operation, the sensor pixel 100 is activated to acquire a readout signal from the sensor pixel 100. In this example, activating the sensor pixel 100 includes applying a scan signal to the sensor pixel 100 to selectively turn it on, and providing the sensor with a supply voltage to the sensor pixel 100, and then outputting a readout signal. Activating the sensor pixel 100 also includes electrically connecting the shield 120 to a reference voltage source. This charges the shield 120 to a reference voltage associated with the reference voltage source (for example, current may flow through the shield connector 122 so that the shield 120 is the reference voltage). The shield 120 capacitively couples with the electrically conductive component 102, but the capacitive sensing electrode 110 is not capacitively coupled with the electrically conductive component 102. If any capacitive coupling exists between the capacitive sensing electrode 110 and the shield 120, the contribution of the shield 120 to this coupling is known because the shield 120 is maintained at the reference voltage. The sensor pixel 100 outputs a readout signal for processing by the sensor readout circuit, and the proximity of the detected object to the capacitive sensing electrode 110 may be determined from the readout signal.

[0042] Another example of a sensor pixel is shown here with reference to Figure 2b.

[0043] Figure 2b shows a sensor pixel 100. The sensor pixel stack for sensor pixel 100 is shown as comprising three electrically conductive layers: a first electrically conductive layer 105a, a second electrically conductive layer 105b, and a third electrically conductive layer 105c. For simplicity, other electrically conductive layers and any intervening layers are not shown. Similar to Figure 2a, the sensor pixel 100 in Figure 2b includes a substrate 101, an electrically conductive component 102, a capacitive sensing electrode 110, and a shield 120. Similarly, the shield connector 122 is shown in Figure 2b.

[0044] The sensor pixel 100 in Figure 2b is the same as that in Figure 2a, except that in Figure 2b the shield 120 is provided in a different conductive layer from the capacitive sensing electrode 110. The shield 120 is provided in a conductive layer below the conductive layer providing the capacitive sensing electrode 110. In this regard, the shield 120 is provided in a second conductive layer 105b, and the capacitive sensing electrode 110 is provided in a third conductive layer 105c.

[0045] The capacitive sensing electrode 110 is located in the topmost conductive layer of the sensor pixel. The shield 120 is located in the layer between the top (third) layer and the bottom (first) layer; for example, the shield 120 is in a vertical layer between the capacitive sensing electrode 110 and the conductive component 102. The shield 120 overlaps the conductive component 102. The mechanism of the first conductive layer 105a does not have to be the same as the mechanism relating to Figure 2a. For example, any conductive element in the first conductive layer 105a may be spatially distributed across the entire area of ​​the sensor pixel, or any conductive element may extend only around the area of ​​the sensor pixel. The shield 120 may extend to the area of ​​the sensor pixel 100 that covers any conductive component in the layer below the shield 120. In other words, the first conductive component 102 may be entirely within the lateral range of the shield 120 (in the layer above the first conductive component 102). For example, the shield 120 may extend over most of the second electrically conductive layer 105b, or it may extend over all of the second electrically conductive layer 105b. For example, the electrical shield 120 may extend over multiple sensor pixels, as will be described in more detail below for later examples (and may also be applied to the example shown in Figure 2a).

[0046] The lateral extent of the shield 120 may encompass most of the area of ​​the sensor pixels covered by the electrically conductive components. For example, the lateral extent of the shield 120 may encompass all the electrically conductive components in the layer below the shield 120. The shield 120 may include one or more openings through which conductive connections between the capacitive sensing electrode 110 and other components of the circuit pass. For example, a conductive via may pass through an opening in the shield 120 from the capacitive sensing electrode 110 to a component in the layer below the sensor pixels. The capacitive sensing electrode 110 overlaps the shield 120. There may be no region of the capacitive sensing electrode 110 that (i) overlaps the electrically conductive component 102 in the layer below the sensor pixel stack and (ii) does not overlap the shield 120 (unless such region of the capacitive sensing electrode 110 is electrically connected to the electrically conductive component 102, for example, through an opening in the shield 102). In other words, the shield 120 may completely (spatially) isolate the capacitive sensing electrode 110 from any electrically conductive components beneath the shield 120. The shield 120 may be the same size as the capacitive sensing electrode 110, smaller than the capacitive sensing electrode 110, or larger than the capacitive sensing electrode 110. For example, the shield 120 may be sized such that it covers all electrically conductive components in the layer beneath it.

[0047] Similar to the sensor pixel 100 in Figure 2a, the shield 120 in the sensor pixel 100 in Figure 2b is positioned to capacitively couple with an electrically conductive component in the layer beneath the shield 120. The shield 120 capacitively couples with the component, preferentially over the capacitive sensing electrode 110 which couples with the component. The sensor pixel 100 is positioned to maintain the shield 120 at a reference voltage while a readout signal is acquired from the readout pixel. The shield 120 may be at a known reference voltage. The shield 120 is positioned to prevent parasitic capacitive coupling between the capacitive sensing electrode 110 and any other electrically conductive element in the layer beneath the shield 120. The sensor may be positioned such that any parasitic capacitive coupling between the capacitive sensing electrode 110 and any other electrically conductive element in the sensor pixel 100 is the coupling between the capacitive sensing electrode 110 and the shield 120. Since the shield 120 is maintained at a fixed voltage while the readout signal is acquired from the sensor pixel, the contribution of the shield 120 to any parasitic capacitive coupling with the capacitive sensing electrode 110 may be known. Any effect this coupling may have on the charge stored in the capacitive sensing electrode 110 during readout may be included as a factor in the resulting measurement. This effect may be determined when the shield 120 is at a known fixed voltage. In other words, the sensor pixel 100 may be arranged such that the shield 120 is a (primary) component of the sensor pixel 100 to which the capacitive sensing electrode 110 is coupled.

[0048] The operation of sensor pixel 100 in Figure 2b may be the same as that in Figure 2a.

[0049] As understood in the context of this disclosure, any mechanism relating to the sensor pixel 100 may provide electrical shielding for the capacitive sensing electrode 110 and thus improve the signal-to-noise ratio relating to the sensor. Advantageously, the mechanism in Figure 2a may require fewer electrically conductive layers, and the capacitive coupling between the shield 120 and the capacitive sensing electrode 110 may be substantially less. Advantageously, the mechanism in Figure 2b may reduce the constraints placed on the spatial layout for each electrically conductive layer. The sensor of this disclosure may comprise either or both types of sensor pixels 100.

[0050] Here, different examples of shields are described with reference to Figures 3 through 5.

[0051] Figure 3 shows a plan view of a portion of a sensor array 10 containing multiple sensor pixels 100. The boundaries of the sensor pixels 100 are indicated by dashed lines in Figure 3. The portion shown in Figure 3 is intended to illustrate different relative mechanisms of the shield 120 and capacitive sensing electrode 110 for one or more sensor pixels 100 of the sensor array 10.

[0052] Figure 3 shows six examples of different configurations relating to the shield 120 and the capacitive sensing electrode 110. Each example is intended to demonstrate a different possible configuration relating to the shield and one or more capacitive sensing electrodes shielded by the shield.

[0053] In the first example, a first capacitive sensing electrode 110a and a first shield 120a are present. In the first example, the sensor pixel 100 may be of the type shown in Figure 2a. The sensor pixel 100 is positioned so that there is no spatial overlap between the first shield 120a and the first capacitive sensing electrode 110a. The first shield 120a is positioned around the sensor pixel, for example, at the corners. However, this is just one example, and alternatively, the first shield 120a may be positioned so that it extends over a larger area around the sensor pixel 100. For example, the first shield 120a may extend over an elongated strip along one or more sides (edges) of the sensor pixel, for example, the first shield 120a may surround the first electrode 110a of the sensor pixel 100. The first capacitive sensing electrode 110a extends over most of the remaining area of ​​the sensor pixel 100 (and also most of the total area of ​​the sensor pixel). Furthermore, any electrically conductive components of the sensor pixel 100 may be placed in the area of ​​the sensor pixel 100 below the first shield 120a. The first shield 120a may be at least partially surrounded by an area that does not contain electrically conductive material. This area may isolate the first shield 120a from the first capacitive sensing electrode 110a. Figure 3 shows one first shield 120a and one first capacitive sensing electrode 110a for each sensor pixel, but it will be understood that the first shield 120a may extend to two or more sensor pixels 100 (i.e., provide shielding for all of the sensor pixels 100). In any case, the first shield 120a may extend to only a subset of the area of ​​each sensor pixel 100 in order to leave space for each of the sensor pixels 100 in the first capacitive sensing electrode 110a in the same electrically conductive layer.

[0054] In the second, third, and sixth examples, different relative dimensions of the shield and the capacitive sensing electrode are shown. In each of these examples, the sensor pixel 100 may be of the type shown in Figure 2b. Thus, each capacitive sensing electrode may be provided in the pixel stack in an electrically conductive layer above the electrically conductive layer where the shield is provided (i.e., with the capacitive sensing electrode above the shield). As previously stated, each shield may contain one or more openings to allow electrical connections between (i) the capacitive sensing electrode in the layer above the shield and (ii) the electrical elements in one or more layers below the shield. In each of these three examples, one shield is shown per sensor pixel. However, it will be understood that instead, each shield may extend to two or more sensor pixels 100 (for example, so that each shield provides shielding for multiple sensor pixels 100).

[0055] In the second example, the second shield 120b is smaller than the second capacitive sensing electrode 110b. The second shield 120b is shown by a dashed line because it lies in a layer below the second capacitive sensing electrode 110b. That is, the area covered by the second shield 120b is smaller than the area covered by the second capacitive sensing electrode 110b. The area covered by the second shield 120b may be entirely contained within the area covered by the second capacitive sensing electrode 110b (as shown in Figure 3). For example, the area covered by the second capacitive sensing electrode 110b may completely surround and encompass the area covered by the second shield 120b. Alternatively, the two areas may overlap, but the area covered by the second shield 120b does not completely fall within the area of ​​the second capacitive sensing electrode 110b. The area and location of the second shield 120b may be selected such that the second shield 120b overlaps any electrically conductive element in the layer beneath the sensor pixel 100 (and therefore, the portion of the second capacitive sensing electrode 110b that does not overlap the second shield 120b does not overlap at all with any electrically conductive element that may be capacitively coupled to it).

[0056] In the third example, the third shield 120c is the same size as the third capacitive sensing electrode 110c (or at least two areas may be substantially the same). The 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 completely overlap.

[0057] In the sixth example, the sixth shield 120f is larger than the 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. Alternatively, one or more portions of the sixth capacitive sensing electrode 110f may not overlap the sixth shield 120f. The sensor pixel 100 may also be positioned such that its portion does not overlap at all with the electrically conductive elements of the sensor pixel 100, which its portion may be capacitively coupled to.

[0058] In the fourth and fifth examples, one shield covers multiple sensor pixels 100.

[0059] In the fourth example, the fourth shield 120d extends to a plurality of sensor pixels 100 and a fourth capacitive sensing electrode 110d associated with the plurality of sensor pixels 100. The fourth shield 120d is for all sensor pixels 100 in a single row. The fourth shield 120d may be arranged such that, for each of the plurality of sensor pixels 100 covered by the fourth shield 120d, the fourth capacitive sensing electrode 110d for that sensor pixel 100 does not overlap the fourth shield 120d, and does not have any region that overlaps with an electrically conductive element in the underlying layer to which the electrode 110d may be capacitively coupled. The fourth shield 120d may cover all or most of each of the fourth capacitive sensing electrodes 110d in a row. For example, the area covered by each of the fourth capacitive sensing electrodes 110d in a row may fall within the area covered by the fourth shield 120d. In other words, one electrically conductive element may provide shielding for each of the multiple sensor pixels 100, for example, for all sensor pixels 100 in one row of the array 10.

[0060] In the fifth example, the fifth shield 120e extends over a plurality of sensor pixels 100 and a fifth capacitive sensing electrode 110e associated with the plurality of sensor pixels 100. The fifth shield 120e may be the same as the fourth shield 120d, except that the fifth shield 120e extends over multiple rows of sensor pixels 100. As shown, the fifth shield 120e does not need to be for all of the sensor pixels 100 in each row. Alternatively, referring to Figure 5, which is not shown in Figure 3 but will be discussed later, the fifth shield 120e may be for all of the sensor pixels 100 in the array 10. For example, the shield may be positioned to prevent parasitic coupling between each capacitive sensing electrode in the array 10 and any other electrically conductive element in the array 10 to which each of the same capacitive sensing electrodes may be capacitively coupled.

[0061] Here, another example of a sensor pixel array is described with reference to Figures 4a and 4b.

[0062] Figure 4a shows a portion of the array 10 of sensor pixels 100. Figure 4a shows the array 10 without any shields 120 or shield connectors 122, which are shown in Figure 4b. Two rows and three columns of sensor pixels 100 are shown in the array 10, but it will be understood that this is only a portion of the array 10 and more rows and columns may be provided. A capacitive sensing electrode 110 is shown for each sensor pixel. Multiple electrically conductive lines are shown for the sensor array 10. These include a scanning line 131, a supply line 132, and a readout line 133. Black-filled circles are used to indicate the electrical connections between the sensor pixels 100 and the associated conductive lines.

[0063] Each sensor pixel 100 in the array 10 may be connected to a plurality of electrically conductive lines. In particular, each sensor pixel 100 may be connected to a scanning line 131, a supply line 132, and a read line 133. Each scanning line 131 may be associated with each row of sensor pixels 100. That is, each scanning line 131 is connected to all sensor pixels 100 in the row of sensor pixels 100. Each row of sensor pixels 100 has an associated scanning line 131. Each supply line 132 may be associated with each column of sensor pixels 100. That is, each supply line 132 is connected to all sensor pixels 100 in the column of sensor pixels 100. Each column of sensor pixels 100 has an associated supply line 132. Each read line 133 may be associated with each column of sensor pixels 100. In other words, each read line 133 is connected to all of the sensor pixels 100 in a row of sensor pixels 100. Each of the rows of sensor pixels 100 has an associated operation line 131.

[0064] To activate a sensor pixel, the sensor is configured to apply a scanning signal to the sensor pixel 100 (via a scanning line 131 connected to the sensor pixel). The scanning signal may also be in the form of a voltage signal. For example, the sensor may be configured to selectively connect the scanning line 131 to a voltage source in order to apply the scanning signal to the scanning line 131. The sensor may be configured to apply the scanning signal to all sensor pixels 100 in a row (connected to the scanning line 131). In addition, to activate a sensor pixel, the sensor is configured to apply a supply signal to the sensor pixel 100 (via a supply line 132 connected to the sensor pixel). Applying a supply signal may include providing a supply voltage to the sensor pixel. For example, 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 all sensor pixels 100 in a column.

[0065] The actuation sensor pixel 100 may also be a sensor pixel 100 that receives a scan signal (from a scan line 131 to which the sensor pixel 100 is connected) and has a supply voltage applied (from a supply line 132 to which the sensor pixel 100 is connected). The actuation sensor pixel 100 is configured to output a read signal (to a read line 133 to which the sensor pixel 100 is connected). The read signal indicates the amount of charge stored in the capacitive sensing electrode 110. This may then provide an indication of the proximity of the conductive object to be detected to the capacitive sensing electrode 110. Each of the read lines 133 may be connected to a processing channel of a read processing circuit configured to process the read signals from the read line 133.

[0066] The sensor is configured to selectively activate each sensor pixel 100 by selectively applying a scanning signal and a supply voltage to different sensor pixels 100. In particular, the sensor may be configured to apply the scanning signal to one scanning line 131 at a time. The scanning signal may charge the scanning line 131 to a selected voltage (for example, a voltage associated with a voltage source connected to the scanning line 131). Alternatively, the sensor may be configured to apply the supply voltage to one or more of the supply lines 132. Each sensor pixel 100 that is both (i) on one of the supply lines 132 and (ii) on a row connected to the scanning line 131 is activated. A readout signal is output from the sensor pixel 100 to a readout line 133 connected to the activated pixel 100.

[0067] In other words, the sensor may be configured to apply a scanning signal (e.g., a fixed voltage) to all sensor pixels 100 in one row of the array 10 at once. The remaining rows of the sensor array 10 may not be activated; that is, they may not have a scanning line 131 that is charged up to the scanning voltage. While one or more read signals are obtained from any activated sensor pixels 100 in the row, the scanning line 131 for that row is the scanning voltage. Only sensor pixels 100 in a row that output read signals may be connected to the activated supply line 132.

[0068] Here, as shown with reference to Figure 4b, this mechanism may be used to selectively maintain the sensor pixel shield 120 at a shield voltage while a readout signal is acquired from a capacitive sensing electrode 110 associated with the shield 120.

[0069] Figure 4b shows the same sensor array 10 as shown in Figure 4a. Figure 4b also shows the sensor array 10 with a shield 120 and a shield connector 122.

[0070] Each row of sensor pixels 100 has an associated shield 120. That is, one shield 120 is provided for all 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 capacitive sensing electrodes 110 in the row of sensor pixels 100. That is, for each row, all capacitive sensing electrodes 110 in that row are shielded by 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 Figure 4b, a shield connector 122 may be provided for each shield 120, which electrically connects the shield 120 for one row to the scan line 131 for that row.

[0071] The sensor is positioned such that the voltage supplied to the sensor pixels 100 in a row (e.g., the scanning voltage that activates at least one of the sensor pixels 100) is also supplied to the shield 120 for that row. In other words, the sensor is positioned so that the activated sensor pixels 100 in a row charge the shield 120 for that row to a selected voltage (i.e., the scanning voltage). This mechanism ensures that the sensor pixels 100 do not need to activate unless the shield 120 for the sensor pixels 100 is also charged to a fixed (and known) voltage. In this example, the shield voltage used for the shield 120 is the scanning voltage applied to the scanning line 131 that activates the sensor pixels 100. The sensor is configured such that the selected voltage (i.e., the scanning voltage) is also applied to the shield 120 while the sensor pixels 100 are activated (i.e., while a scanning signal is applied to the sensor pixels), and therefore the sensor is configured to maintain the shield 120 at the selected voltage while a readout signal is acquired from the activated sensor pixels.

[0072] During operation, the sensor processes one row at a time. For the first row, a scan 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 different columns having pixels 100 in that row. The working pixels 100 in that row receive both (i) the scan signal from the scan line 131 for that row and (ii) the supply voltage from the supply line 132 for that row. Each working pixel 100 then outputs a read signal to its respective read line 133 for processing by the sensor's readout circuit.

[0073] As the scanning signal is applied to the sensor pixel 100 in the row via the scanning line 131 for that row, the same scanning signal is also applied to the shield 120 for that row. Thus, the shield 120 is charged up to the scanning voltage. There may be an initial period during which the voltage of the shield 120 changes (i.e., increases or decreases) and that voltage is the scanning voltage. However, in practice, it will be understood that this change occurs rapidly. For the remainder of the time while the scanning signal is applied to the scanning line 131 (and thus while the pixel 100 in the row may be activated to output a read signal), the shield 120 is maintained at the scanning voltage.

[0074] Therefore, while a readout signal indicating the amount of charge stored in the capacitive sensing electrode 110 is acquired, the shield 120 is at a fixed voltage. Thus, any capacitive coupling between the shield 120 and the capacitive sensing electrode 110 occurs at one of the active plates of this capacitor, which is held at a fixed, constant, and known voltage (i.e., the scanning voltage). Thus, since the voltage for one of the capacitor's plates is known, and the other plate provides the parameter to be measured (i.e., the amount of charge stored on that plate), any effect of this capacitive coupling may also be known. At the same time, due to the mechanism of the shield 120 shielding the capacitive sensing electrode 110, less parasitic capacitive coupling may occur between the capacitive sensing electrode 110 and other electrically conductive components of the sensor pixel of the capacitive sensing electrode 110. Thus, by fixing the shield 120 at a known voltage, there may be fewer unknown noise sources in the resulting measurements acquired from the sensor array 10.

[0075] The method may then be continued by activating different sensor pixels 100 in the array 10. After the activated pixels 100 in the first row output a read signal to the read line 133 of each activated pixel 100, the sensor may apply a scan signal to the next scan line 131. For example, the sensor may process the sensor pixels 100 row by row. When the activated sensor pixels 100 in the first row output a read signal, the sensor pixels 100 in the second row may be activated. This process may be repeated for all rows in the sensor array 10. The process may be repeated several times for each row, so that each time a row is processed, the first subset of sensor pixels 100 in that row output a read signal, and then, the next time the row is processed, the different subset of sensor pixels 100 in that row output a read signal. By repeating this process, at least one readout signal may be output and processed from each of the sensor pixels 100 in the array 10 (or at least many, e.g., for most) in the array 10. At each step in the method of activating a particular subset of sensor pixels 100 in the array 10, the shield 120 for the activated sensor pixel 100 is maintained at the scanning voltage (because the same scanning signal that activates the sensor pixel 100 is also applied to the shield 120 for the activated sensor pixel 100).

[0076] Another exemplary sensor array is shown in Figure 5.

[0077] Figure 5 shows a sensor array 10 containing multiple sensor pixels 100. The boundaries of the sensor pixels 100 are indicated by dashed lines. Figure 5 also shows a capacitive sensing electrode 110 and a shield 120 for each sensor pixel 100. In the example of Figure 5, the shield 120 covers the entire sensor array 10. In other words, each sensor pixel 100 has its own shield 120 provided by the same single electrically conductive element.

[0078] Furthermore, the voltage source 124 and the interference protection circuit 140 are shown in Figure 5. The interference protection circuit 140 may include multiple diodes that connect the shield 120 to the sensor's voltage rail. Inset A in Figure 5 shows the interference protection circuit 140 having a first (e.g., high) voltage rail 141 and a second (e.g., low) voltage rail 142. The circuit shown in inset A also includes a high diode 141a and a low diode 142a.

[0079] The shield 120 extends across the entire sensor array 10 so that it provides electrical shielding for all capacitive sensing electrodes 110 in the array 10. For example, the shield 120 may be provided by an electrically conductive layer covering the entire area (or at least a large portion) of the sensor array 10. The sensor in Figure 5 may be configured to operate in the same manner as the sensor described above, for example, in that the sensor pixel 100 may be activated by receiving a scanning signal on the scanning line of the sensor pixel 100 and a supply voltage on the supply line of the sensor pixel 100. In Figure 5, one connection is shown between the shield 120 and the voltage source 124. However, multiple such connections may be present.

[0080] The voltage source 124 may also be a control voltage source, for example, a voltage source configured to set the shield 120 to a selected voltage. The control voltage source 124 is configured to control the voltage of the shield 120 so that the selected voltage (i.e., the shield voltage) is a constant voltage while a readout signal is acquired from the work pixel 100. The voltage source 124 may be provided by another voltage source used within the sensor, for example, a voltage source for the scan signal or a supply voltage source. As another example, the voltage source 124 may also be electrical ground, for example, so that the connection of the shield 120 to electrical ground grounds any voltage of the shield 120 (for example, to 0V). The voltage source 124 may also be a separate voltage source. For example, the voltage source 124 may be a voltage source dedicated to the shield 120.

[0081] In an example where the voltage source 124 is also used to supply voltage to other components of the sensor, for example, where the voltage source 124 provides a scanning voltage or supply voltage to the sensor pixel 100, the shield 120 may have several different electrical connections to the voltage source 124. For example, an electrical connection (e.g., direct or indirect) may exist between the shield 120 and the scanning voltage source so that whenever the scanning voltage is applied to any row of the rows in the sensor array 10, the same scanning voltage is also provided to the shield 120 through the same electrical connection.

[0082] Similarly, if the shield 120 is electrically connected to receive the supply voltage, the shield 120 may be connected to all supply lines in the sensor array 10. Alternatively, the shield 120 may be connected to only a portion of the supply lines, but these supply lines are selected so that the shield 120 receives the supply voltage for all working pixels. For example, since multiple supply lines may be activated at any given time to activate a sensor pixel 100, the shield 120 may simply be connected to only a portion of the supply lines so that it always receives the supply voltage when the sensor pixel 100 is activated. Furthermore, or alternatively, a direct electrical connection may exist between the shield 120 and the supply voltage source so that whenever the supply voltage is applied to any of the columns in the sensor array 10, the supply voltage is also provided to the shield 120 via that direct connection.

[0083] In any of these examples, the sensor is positioned such that the shield 120 is maintained at the shield voltage of the shield 120 while a readout signal is acquired from the operating sensor pixel 100 in the array 10. Since the shield 120 covers all of the capacitive sensing electrodes 110 of the sensor array 10, it will be understood that any subset of sensor pixels 100 in the array 10 may be operating at any given time, and the single shield 120 still provides electrical shielding for those sensor pixels 100.

[0084] As described above, the sensor may operate by activating the sensor pixels 100 in the first row, then the sensor pixels 100 in the next row, and so on, until a read signal is acquired from a desired number / percentage of sensor pixels 100 in the array 10. For example, the process may be repeated iteratively until a read signal is acquired from all sensor pixels. Each time a read signal is acquired from an activated sensor pixel, the shield 120 is maintained at the shield voltage of the shield 120. Each subsequent activation of a sensor pixel 100 may occur very quickly, and for example, it will be understood in the context of this disclosure that as a result, a read signal is acquired from all of the sensor pixels 100 in a relatively short period of time. 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 to charge / discharge the shield 120 to the shield voltage between the activations of the next sensor pixels. For example, when one sensor pixel has finished operating, the shield 120 is at the shield voltage, and since the operation of the next sensor pixel occurs very soon thereafter, the shield voltage is unlikely to change significantly between the end of operation of one sensor pixel and the start of operation of the next sensor pixel. This may reduce the overall power consumption required to provide the sensor.

[0085] In the examples described herein, one or more shields 120 are included to provide electrical shielding for the capacitive sensing electrode 110 from parasitic coupling with other elements of the sensor, such as other electrically conductive components within the sensor (e.g., the electrical elements of the sensor pixel 100 and / or lines providing electrical connections to the sensor pixel). The shields of this disclosure may have further properties to facilitate improved operation of the sensor. The following examples are described primarily with reference to the shield 120 in Figure 5, but it will be understood that the following examples may apply to any of the shields 120 disclosed herein.

[0086] In some examples, the shield 120 may be configured to provide interference protection. In particular, the shield 120 may be configured to provide protection from undesirable electrical effects such as electrostatic discharge and / or electromagnetic interference. In this regard, the sensor may also include an interference protection circuit 140 of the type shown in Figure 5. The interference circuit is configured to selectively provide an electrical conduction path away from the shield 120 in the event of deviations exceeding a threshold level. For example, if the voltage across the shield 120 is higher than an upper threshold voltage or lower than a lower threshold voltage (e.g., a negative threshold voltage), the protection circuit 140 is configured to divert excess current away from the shield 120.

[0087] As shown in inset A of Figure 5, the interference protection circuit 140 may be formed of one or more diodes connecting the shield 120 to a first (e.g., high) voltage rail 141 and one or more diodes connecting the shield 120 to a 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 as a short-circuit transistor in inset A. Similarly, 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 short-circuit transistor. Two or more short-circuit transistors may be arranged in series to connect the shield 120 to the high / low rails respectively.

[0088] The interference protection circuit 140 is positioned to provide an electrical conduction path away from the shield 120. The high diode 141a is positioned to provide a conduction path between the shield 120 and the high-voltage rail 141. If the voltage across the shield 120 exceeds a threshold voltage (for example, if the shield voltage is higher than the voltage across the high rail), current may flow away from the shield 120 through the high diode 141a to the high-voltage rail 141. Similarly, the low diode 142a is positioned to provide a conduction path between the low-voltage rail 142 and the shield 120 to divert current so as to prevent the voltage across the shield 120 from falling below a threshold voltage (for example, if the voltage across the shield 120 becomes too negative).

[0089] In other words, the sensor may be configured to utilize the shield 120, the interference protection circuit 140, and any of these electrical elements to provide electrical protection for the sensor. For example, the sensor may be configured to utilize the shield 120 and the interference protection circuit 140 to provide shielding for the sensor from electrostatic discharge and / or electromagnetic interference.

[0090] In some examples, the shield 120 may be provided by an opaque material. For example, a conductive but opaque metal may be used. In other words, the shield 120 may be positioned to provide optical shielding to the components beneath the shield 120. If one or more TFTs are included in the sensor pixel 100, the sensor shield 120 may be positioned to overlap the components, in particular, to overlap the channel region of the TFT. This positioning not only provides electrical shielding from capacitive coupling between the capacitive sensing electrode 110 and the TFT, but additionally, if the shield 120 is opaque (e.g., opaque to visible light), it may also improve the operating characteristics of the TFT. For example, certain performance characteristics may be affected by optical rays incident on the TFT. That is, the operation of the TFT may change depending on the incident light, and / or the TFT may degrade over time due to continuous exposure to ambient light. In other words, the shield 120 may provide optical protection for the sensor, for example, to protect the components beneath the shield 120 from incident light. The incident light may be visible light and / or ultraviolet light (and / or electromagnetic radiation in other parts of the EM spectrum).

[0091] In some examples, the shield 120 may be positioned to facilitate touch-sensitive operation. For example, touch detection may be detected using the shield 120. This may be particularly useful when the shield 120 covers a larger area of ​​the sensor array 10 (for example, when the shield 120 covers multiple sensor pixels 100), for example, when the shield 120 covers the entire array 10, or when the shield 120 covers each row / column. Capacitive sensing electrodes 110 may be provided to enable biometric identification from the same sufficiently high spatial resolution data based on acquired fingerprint data, for example, with a spatial resolution high enough to facilitate biometric scanning, for example, when sufficiently high spatial resolution data is acquired about an object in contact with the sensor. The sensor may also be configured to operate in touch-sensitive mode. In touch-sensitive mode, the sensor may be configured to identify when an object is interacting with the sensor, for example, in contact with it. In this regard, the sensor may be configured to use the shield 120 of the sensor array 10. For example, the use of the sensor shield 120 for detecting contact may be an alternative to, or additional to, the use of, the capacitive sensing electrode 110 for this purpose.

[0092] 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 electrode 110 is used for capacitive sensing. The first mode may be used for contact sensing (for example, to detect indication of contact between an object and the sensor). The second mode may be used for capacitive biometric skin contact sensing. The sensor may be configured to initially operate in the first mode until indication of contact is detected, and then switch to the second mode. For example, the controller may be configured to detect contact in the first mode and, when indication of contact is detected, switch to the second mode to perform higher spatial resolution sensing (for example, to perform capacitive biometric skin contact sensing of an object in contact with the sensor).

[0093] Numerous different examples of sensors are described herein, but it should be understood that these examples should not be considered limiting. Further or alternative mechanisms may be provided. For example, the use of a shield 120 to prevent capacitive coupling between a capacitive sensing electrode 110 and an electrically conductive component of the sensor (e.g., an electrically conductive component 102) is generally mentioned. It will be understood that the shield 120 is positioned to provide preferential capacitive coupling with respect to parasitic capacitance. For example, any capacitive coupling from a component of the sensor pixel 100 may be between that component and the shield 120 rather than between that component and the capacitive sensing electrode 110. However, the shield 120 does not have to completely eliminate 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 positioned to minimize the amount of this remaining coupling.

[0094] Furthermore, parasitic coupling with electrically conductive components 102 is also generally referred to. For example, it will be understood in the context of this disclosure that there may be multiple different capacitive coupling sources, including one or more TFTs, conductive lines, capacitors, etc., that provide sensor pixels 100 and extend to the sensor array 10. The shield 120 is positioned to minimize the amount of parasitic coupling with the capacitive sensing electrode 110 from any potential parasitic coupling sources. For example, the sensor may be positioned such that the shield 120 overlaps all of the components, for example, so that the shield 120 preferentially capacitively couples with all of the said parasitic sources. Also, as will be understood, the components may include any relevant components of the sensor with which the capacitive sensing electrode 110 capacitively couples. In other examples, the sensor may provide different forms of sensing for capacitive sensing. For example, each sensor pixel 100 may comprise a sensor element such as an optical sensor detector (instead of the capacitive sensing electrode 110), and the sensor may be configured to provide shielding for the sensor element from other components of the sensor.

[0095] It will be understood that the shielding voltage may be any suitable voltage. The shield 120 is an "active shield" in the sense that it is actively connected to an appropriate component to maintain the shielding voltage when shielding the capacitive sensing electrode 110 (for example, the shield 120 is not merely floating). The shielding voltage may be a positive voltage or zero. The shield 120 may be connected to one or more electrically conductive lines of the sensor array 10 to set the shield 120 to a fixed shielding voltage of the shield 120. For example, if the shielding voltage is positive, the shield 120 may be connected to a positive voltage source (e.g., a scanning line or a supply line), and if the shielding voltage is zero, the shield 120 may be connected to a ground voltage (e.g., the ground line of a grounded sensor). Alternatively, the shield 120 may be connected to a separate voltage source or other suitable voltage source to maintain the shielding voltage of the shield 120. The shield 120 may be connected to multiple conductive lines, such as multiple scanning lines and / or supply lines. The shield 120 may be permanently maintained at the shield voltage (rather than being selectively connected to a reference voltage source when the sensor pixels 100 are operating, for example). Alternatively, in the above example, one shield 120 may be provided for each row of sensor pixels 100. Alternatively, a shield 120 may be provided for each column of sensor pixels 100, for example, each shield 120 may be connected to a supply line for the column of sensor pixels 100 so that the shield 120 is charged to a supply voltage for shielding.

[0096] From the above description, it will be understood that the examples shown in the figures are merely illustrative and may include features that may be generalized, deleted, or replaced as described herein and in the claims. Referring to the figures as a whole, it will be understood that the schematic functional block diagrams are used to illustrate the functions of the systems and devices described herein. Processing functions may also be provided by devices supported by electronics. However, it will be understood that functions do not need to be divided in this way and should not be interpreted as suggesting any specific hardware structure other than those described below and in the claims. One or more functions of the elements shown in the figures may be further subdivided and / or distributed throughout the entire device of this disclosure. In some examples, the functions of one or more elements shown in the figures may be integrated into a single functional unit.

[0097] As will be understood by those skilled in the art in the context of this disclosure, each example described herein may be implemented in a variety of different ways. Any feature of any aspect of this disclosure may be combined with any other aspect of this disclosure. For example, a method aspect may be combined with an apparatus aspect, and a feature described in reference to the operation of a particular element of the apparatus may be provided in a way that does not use a particular type of apparatus. Furthermore, unless it is expressly stated that some other feature is essential to the operation of the feature, each feature relating to each example is intended to be separable from the feature to which each feature is combined. Each separable feature may, of course, be combined with any other feature of the example to which each separable feature is described, or with any or a combination of other features relating to any other example described herein. Furthermore, equivalents and modifications not described herein may be adopted without departing from the invention.

[0098] Certain features of the methods described herein may be implemented in hardware, and one or more functions of the apparatus may be implemented in method steps. It will also be understood in the context of this disclosure that the methods described herein do not necessarily have to be performed in the order in which they are described, nor do they necessarily have to be performed in the order in which they are depicted in the drawings. Thus, aspects of this disclosure described with reference to a product or apparatus are also intended to be implemented as methods, and vice versa. The methods described herein may be implemented as computer programs or hardware, or any combination thereof. Computer programs include software, middleware, firmware, and any combination thereof. The programs may be provided as signals or network messages, or may be recorded on computer-readable media such as tangible computer-readable media that may store computer programs in a non-temporary form. Hardware includes computers, handheld devices, programmable processors, general-purpose processors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and arrays of logic gates.

[0099] Other examples and modifications of this disclosure will be obvious to those skilled in the art in the context of this disclosure.

Claims

1. A capacitive sensor comprising an array of multiple sensor pixels, Each sensor pixel is, Capacitive sensing electrode, A shield having conductivity and positioned to electrically shield the capacitive sensing electrode from parasitic coupling with other elements of the sensor, Equipped with, The sensor is configured to maintain the shield at a shield voltage while a readout signal is being acquired from the sensor pixel. A capacitive sensor characterized by the following features.

2. The sensor spans the array, Multiple conductive lines, Equipped with, The shield is connected to at least one of the conductive lines. The sensor according to claim 1.

3. At least one of the conductive lines electrically connects the shield to a control voltage source. The sensor according to claim 2.

4. At least one of the conductive lines is (i) One or more scanning lines, (ii) One or more grounding lines, (iii) One or more voltage supply lines, Equipped with, The sensor according to claim 3.

5. The shield overlaps the other elements of the sensor. The sensor according to any one of claims 1 to 4.

6. The shield is provided in the same layer as the capacitive sensing electrode. The sensor according to any one of claims 1 to 5.

7. The shield is provided in a layer between the capacitive sensing electrode and the other elements of the sensor. The sensor according to any one of claims 1 to 5.

8. The capacitive sensing electrode is placed on top of the shield, The sensor according to claim 7.

9. A single electrically conductive element provides the shield to multiple sensor pixels. The sensor according to any one of claims 1 to 8.

10. A single electrically conductive element provides the shield to all of the sensor pixels in the array. The sensor according to claim 9.

11. A single electrically conductive element is connected to multiple conductive lines across the array of sensors. The sensor according to claim 10.

12. A single electrically conductive element provides the shield to all of the sensor pixels in a row. The shield is connected to the scan line for the row, The sensor according to claim 9.

13. The sensor is configured to operate in a first mode in which the shield is used to perform capacitive contact detection. The sensor according to any one of claims 1 to 12.

14. When operating in the first mode, the sensor is configured to switch to a second mode in which the capacitive sensing electrode is used to perform capacitive biomedical skin contact detection, in response to the acquisition of a contact indication. The sensor according to claim 13.

15. Each of the sensor pixels' shields substantially blocks visible light and / or ultraviolet light. The sensor according to any one of claims 1 to 14.

16. Each of the sensor pixels' shields is arranged to provide shielding from electromagnetic and / or electrostatic interference. The sensor according to any one of claims 1 to 15.

17. The shield is coupled to the high-voltage rail and the low-voltage rail, respectively, via one or more diodes arranged to provide protection against electrical interference. The sensor according to claim 16.

18. The circuit for the aforementioned sensor pixel is: At least one thin-film transistor TFT, Equipped with, The shield is positioned to electrically shield the capacitive sensing electrode from parasitic coupling with the TFT. The sensor according to any one of claims 1 to 17.

19. A capacitive sensing method using an array of multiple sensor pixels, Each sensor pixel is, (i) Capacitive sensing electrode, (ii) A shield having conductivity and arranged to electrically shield the capacitive sensing electrode from parasitic coupling with other elements of the sensor, Equipped with, The aforementioned method, To provide the electrical shield of the capacitive sensing electrode, the shield is maintained at a shielding voltage while a readout signal is being acquired from the sensor pixel. including, A method for detecting capacity, characterized by the features described above.

20. The shield is connected to a control voltage source in order to maintain the shield at the shield voltage. The method according to claim 19.

21. The shield is connected to the control voltage source by one or more conductive lines across the array of sensors. The method according to claim 20.

22. The shield is connected to the control voltage source to maintain the shield at the shield voltage while the readout signal is being acquired from the sensor pixel, by (i) one or more scanning lines, (ii) one or more ground lines, or (iii) one or more voltage supply lines. The method according to claim 21.

23. The shield is used to obtain an indication of contact with the array of sensors, and then the capacitive sensing electrode is used to perform biometric measurement detection after the indication of contact has been detected. including, The method according to any one of claims 19 to 22.

24. Maintaining the shields of multiple sensor pixels simultaneously at the shield voltage, including, The method according to any one of claims 19 to 23.

25. Computer program instructions configured to control a capacitive biometric skin-contact sensor in order to perform the method according to any one of claims 19 to 24, Having, A computer program product characterized by the following features.

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