Sensor and method

Abstract

A capacitive sensor comprising an array of sensor pixels, wherein each sensor pixel comprises: a capacitive sensing electrode; and 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; wherein the sensor is configured to maintain the shield at a shielding voltage while a read-out signal is being obtained from the sensor pixel.

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 such sensors. [Previous Technology]

[0002] International Publications 2020 / 178605 and 2022 / 043699 of the Patent Cooperation Treaty (PCT) disclose examples of various capacitive biometric skin contact sensors. These sensors are operable to acquire capacitance measurements of a sensor array spanning a large area. Based on these capacitance values, biometric data can be acquired when a user touches the sensor. For example, differences between bulges and depressions in the user's skin contour can be identified based on differences in capacitance values ​​measured on the sensor array. Such sensors can achieve biometric verification by comparing the acquired skin contour distribution with known skin contour distributions. For example, the sensor could be a fingerprint sensor that identifies a user based on their fingerprint. The sensor pixels disclosed in these two prior art are specifically designed to have a high signal-to-noise ratio when measurements are performed using the sensor pixels.

[0003] The purpose of this disclosure is to provide an improvement over this type of prior art sensor. [Summary of the Invention]

[0004] The aspects of this disclosure are set forth in the independent items and the optional features are set forth in the appendices. The aspects of this disclosure may be provided in combination with each other, and the features of one aspect may be applied to the other aspects.

[0005] In one embodiment, this disclosure provides a capacitive sensor including an array of a plurality of sensor pixels, each sensor pixel including: a capacitive sensing electrode; and a shielding cover, which is conductive and configured to electrically shield the parasitic coupling between the capacitive sensing electrode and other components of the sensor. The sensor is configured to maintain the shielding cover at a shielding voltage when a readout signal is obtained from the sensor pixel.

[0006] The sensor is configured to maintain the shield at a shielding voltage, causing parasitic capacitive coupling between the shield and the capacitive sensing electrode, wherein one side of the equivalent capacitance is maintained at a known voltage. That is, the shield is maintained at the shielding voltage. The other side of the equivalent capacitance (capacitive sensing electrode) stores a charge, representing the proximity of the conductive object to be sensed to the electrode. The amount of charge stored on the capacitive sensing electrode may also be affected by its capacitive coupling with the shield. By maintaining the shield at a fixed and constant voltage, the parasitic coupling between the capacitive sensing electrode and the shield can be a known quantity. Therefore, the effect of this parasitic coupling on the amount of charge stored on the capacitive sensing electrode can be known. This effect can be compensated for. For example, a readout signal indicates a certain amount of charge stored on the capacitive sensing electrode, so the sensor can determine the effect of capacitive coupling on the quantity. Thus, this allows for a better assessment of the effect of the proximity of the conductive object to be sensed on the amount of charge stored on the capacitive sensing electrode.

[0007] This embodiment can achieve an effective increase in the signal-to-noise ratio, which can be obtained from the complex readout signals of the complex sensor pixels of the array. Moreover, this can provide a greater dynamic range for measurements obtained using the sensors. In other words, for each given readout signal, the influence of noise sources from unknown and / or unquantifiable sources on the readout signal will be reduced. Conversely, noise in the signal associated with capacitive coupling between the capacitive sensing electrode and the shield will be a known quantity that can be compensated for. Therefore, this setup can increase the signal-to-noise ratio of measurements obtained from the sensors. A greater dynamic range can also be obtained from the sensors because a greater response of each readout signal to changes in stored charge on the capacitive sensing electrode can be derived from the acquired complex readout signals.

[0008] The shielding voltage can be a fixed voltage, such as a DC voltage. Maintaining the shield at the shielding voltage when a readout signal is obtained from the sensor pixel may include operating the sensor such that the shield is connected to a voltage source when the readout signal is obtained. The voltage source can be a DC voltage source. It can be a voltage source that also provides voltage to other elements of the sensor array; it can be a separate voltage source for the shield, or it can be electrically grounded. The sensor can be configured to simultaneously activate the sensor pixel to output a readout signal and connect the shield of the sensor pixel to a shielding reference voltage source. For example, the sensor can be configured to apply one or more electrical signals to activate the sensor pixel, and the application of the electrical signals also serves to maintain the shield at the shielding voltage. For example, the sensor can be configured to electrically connect the shield to a shielding voltage source such that when a readout signal is obtained from the sensor pixel, the shielding voltage source can charge / discharge / both to the shielding voltage and then maintain the shield at the shielding voltage.

[0009] The sensor may include a plurality of conductive lines spanning an array. A shield may be connected to at least one of the conductive lines. At least one conductive line may be electrically connected to the shield to a controlled voltage source. For example, it may connect the shield to a DC voltage. For example, the controlled voltage source may be configured to control the shield to a selected voltage (e.g., a fixed set voltage) once electrically connected to the shield. At least the conductive lines may include: (i) one or more scan lines 131, (ii) one or more ground lines, or (iii) one or more voltage supply lines.

[0010] The shield may cover other components of the sensor. For example, other components may be located below the shield (e.g., vertically below the shield). The top surface of the sensor may be a contact surface that contacts the object to be sensed. The shield may be disposed in the same layer as the capacitive sensing electrode. The shield may be disposed in a layer between the capacitive sensing electrode and other components of the sensor. The capacitive sensing electrode may cover the shield. For example, the shield may vertically separate the capacitive sensing electrode from other components of the sensor.

[0011] A single conductive element can provide a shield for a plurality of sensor pixels. A single conductive element can provide a shield for all sensor pixels in an array; for example, the sensor array can have multiple shields for electrically shielding all capacitive sensing electrodes in the array. A single conductive element can be connected to a plurality of conductive lines spanning the sensor array. A single conductive element can provide a shield for all sensor pixels in a column, wherein the shields can be connected to the scan lines of the column.

[0012] The sensor may be a capacitive touch sensor. Each readout signal may represent the amount of charge stored on the capacitive sensing electrode. Each readout signal may provide an indication of the proximity of the object to be sensed 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 a shield is used to perform capacitive contact sensing. When operating in the first mode, in response to a contact indication, 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 sensing. The shield of each sensor pixel may be substantially opaque to visible light and / or ultraviolet light. The shield of each sensor pixel may be configured to shield electromagnetic waves and / or electrostatic interference. The shield may be coupled to a high-voltage rail and a low-voltage rail by being configured to provide electrical interference protection for one or more diodes. The circuitry of the sensor pixel may include at least a thin-film transistor (TFT). The shield is configured to electrically shield the parasitic coupling between the capacitive sensing electrode 110 and the TFT. The complex thin-film transistors disclosed herein may include at least one of the following types of thin-film transistors: (i) oxides, such as indium gallium zinc oxide (IGZO), (ii) amorphous silicon (aSi), (iii) (low-temperature) polycrystalline silicon (LTPS / pSi), (iv) combinations of low-temperature polycrystalline silicon (LTPS) and oxides, such as low-temperature polycrystalline oxide (LTPO), and (v) organic materials.

[0013] The sensor may include an array of multiple sensor pixels, each sensor pixel comprising one or more thin-film transistors (TFTs) and capacitive sensing electrodes. The sensor pixels may be arranged in an active matrix array, wherein the sensor may operate to address the pixels by applying a scan signal to each pixel. Each addressed pixel may also receive a supply voltage from a supply line. Each addressed pixel may output a readout signal to a readout line. For each sensor pixel, the readout signal may represent the proximity of the sensed conductive object to the capacitive sensing electrode of the sensor pixel. The sensor may include readout circuitry configured to process the readout signal.

[0014] For example, each sensor pixel may include at least one thin-film transistor that controls the readout signal from the sensor. This may include a "sensing thin-film transistor" configured to output the readout signal to a readout line. When each pixel is addressed by a scan signal (along a scan line connected to the pixel) and receives a supply voltage (from a supply line connected to the pixel), the sensing thin-film transistor may output the readout signal to the readout line connected to it. A capacitive sensing electrode may be coupled to the gate region of the sensing thin-film transistor, so the amplitude of the readout signal from the sensing thin-film transistor to the readout line may be affected by the equivalent capacitance of the capacitive sensing electrode (i.e., this can therefore represent the proximity of the conductive object to be sensed to the capacitive sensing electrode). The sensor may be configured to iteratively execute a program for different complex sensor pixels to obtain readout signals from each sensor pixel in the array.

[0015] In one embodiment, a capacitive sensing method is provided, using an array of multiple sensor pixels, each sensor pixel including: (i) a capacitive sensing electrode; and (ii) a shield that is conductive and configured to electrically shield parasitic coupling between the capacitive sensing electrode and other elements of the sensor. The method includes maintaining the shield at a shielding voltage to provide electrical shielding of the capacitive sensing electrode when a readout signal is obtained from the sensor pixel.

[0016] The shield can be connected to a controlled voltage source to maintain the shield at a shield voltage. The shield can be connected to the controlled voltage source via one or more conductive lines across the sensor array. The shield can be connected to: (i) one or more scan lines, (ii) one or more ground lines, or (iii) one or more voltage supply lines, to maintain the shield at the shield voltage when a read signal is obtained from the sensor pixels. The method may include using the shield to obtain a contact indication of the sensor array, and then performing biometric sensing using capacitive sensing electrodes after the contact indication is detected. The method may include simultaneously maintaining the shield at the shield voltage for multiple sensor pixels.

[0017] Aspects of this disclosure may include one or more computer program products, including a plurality of computer program instructions configured to control the capacitive biometric skin contact sensor to perform any of the methods disclosed herein.

Implementation Method

[0027] This disclosure relates to the use of an active shield on a capacitive sensor pixel. The shield is configured to suppress capacitive coupling between the capacitive sensing electrode within the sensor pixel and other adjacent elements of the sensor, such as other conductive elements of the sensor pixel itself. Conversely, the shield is configured to capacitively couple with such other conductive elements of the sensor pixel. When a readout signal is obtained from the sensor pixel, the shield is maintained at a fixed and known voltage. During this period, the value of any capacitive coupling between the capacitive sensing electrode and the shield can be precisely determined because the shielding voltage is known and fixed, and the shield suppresses capacitive coupling between the capacitive sensing electrode and other conductive elements of the sensor at unknown voltages. Therefore, this reduces the amount of noise in the charge stored on the capacitive sensing electrode of the sensor pixel when the readout signal indication occurs.

[0028] An example of sensor pixel design will be described with reference to Figures 2a and 2b, but first an example of a sensor array will be described with reference to Figure 1.

[0029] FIG1 shows a plan view of a portion of a sensor array including a plurality of sensor pixels 100. Each sensor pixel 100 is shown as having a capacitive sensing electrode 110. For simplicity, other elements of the sensor array 10, including the elements in each sensor pixel 100, are not shown in FIG1.

[0030] The sensor array 10 includes a plurality of columns of sensor pixels 100 and a plurality of rows of sensor pixels 100. Each sensor pixel 100 can provide its own sensing area on the sensor array 10, for example, each sensor pixel 100 can be configured to provide sensing of a subset of all areas of the sensor array. The capacitive sensing electrode 110 of each sensor pixel 100 can occupy most of the area of ​​the sensor pixel 100 (when viewed from a plane). By increasing the area covered by the capacitive sensing electrode 110, more charge can be stored on the capacitive sensing electrode 110. The area covered by each individual capacitive sensing electrode 110 can also be limited so that the spatial resolution of the capacitive sensor is high enough to provide biometric sensing (e.g., for recognizing the contours of a user's skin).

[0031] Each sensor pixel 100 is configured to output a readout signal that can represent the amount of charge stored on its capacitive sensing electrode 110. This can further provide an indication of the proximity of the conductive object to be sensed to the capacitive sensing electrode 110. The sensor array 10 may include an active matrix array of a plurality of sensor pixels 100. Each sensor pixel 100 can be selectively activated, and a readout signal can be obtained from each sensor pixel 100. The sensor can be configured to activate different of the plurality of sensor pixels 100 simultaneously. For example, the sensor can be configured to activate each sensor pixel 100 in each column simultaneously. A readout signal can then be obtained from each sensor pixel 100 in the column. For example, a readout signal can be obtained from some or all of the sensor pixels 100 in a column.

[0032] Each sensor pixel 100 may include one or more electronic elements configured to output a readout signal that may represent the amount of charge stored on the capacitive sensing electrode 110. The readout signal may be, for example, an electrical signal, such as a current or voltage signal. For example, the readout signal may be in the form of a current signal, wherein, for example, the amplitude of the current in the signal provides an indication of the amount of stored charge. Each sensor pixel 100 may include one or more thin-film transistors (TFTs). Each sensing element may also include other types of electronic elements, such as capacitors. Furthermore, the sensor array 10 may include a plurality of conductive lines electrically connected to the sensor pixel 100 to activate the sensor pixel 100 and transmit a plurality of readout signals from it to the sensor's readout circuitry.

[0033] Each sensor pixel 100 may include a multi-layer pixel stack. The pixel stack of each sensor pixel 100 may include a plurality of conductive layers (e.g., metallization layers). Different electronic components may be disposed across the plurality of conductive layers. Each conductive layer may be separated from adjacent conductive layers through an intermediate layer. The (plural) intermediate layers may include an insulating material. The stack may also include a semiconductor material for providing one or more thin-film transistors for the stack. The top surface of the sensor may be configured to contact the object to be sensed. The capacitive sensing electrode 110 of each sensor pixel 100 may be configured in the topmost conductive layer of the stack (e.g., such that there is no intermediate conductive layer between the capacitive sensing electrode 110 and the object to be sensed). Other plurality of conductive elements of the stack may be disposed in one or more conductive layers below the topmost conductive layer (e.g., in a layer below the capacitive sensing electrode 110).

[0034] The complex sensor disclosed herein includes a shield configured to electrically shield the parasitic coupling between the capacitive sensing electrode 110 and other elements of the sensor. Specifically, the shield may electrically shield the capacitive sensing electrode 110 of the sensor pixel 100 from other elements in the sensor pixel (e.g., one or more transistors and / or capacitors). For this purpose, the shield may be configured to be capacitively coupled to the sensor element itself. The sensor is configured to maintain a shielding voltage so any capacitive coupling between the capacitive sensing electrode 110 and the shield will occur when the shield is at a known reference voltage. Thus, the effect of capacitive coupling of the shield will be known (because the reference voltage of the shield is known), while the effect of the second equivalent plate of the capacitor will be unknown if capacitive coupling occurs with other elements of the sensor, because the amount of stored charge of the element may vary.

[0035] Examples of different sensor pixel arrangements containing similar shields will now be described with reference to Figures 2a and 2b. In Figure 2a, the sensor pixels are arranged such that the capacitive sensing electrode 110 is laterally offset from an electronic component that can be capacitively coupled, and the component is laterally aligned with the shield. In Figure 2b, the sensor pixels are arranged such that the shield is located in an intermediate layer between the capacitive sensing electrode 110 and the component.

[0036] FIG2a shows a cross-sectional view of sensor pixel 100. The sensor pixel stack of sensor pixel 100 is shown as including two conductive layers: a first conductive layer 105a and a second conductive layer 105b. For simplicity, no other multiple conductive layers or any intermediate layers are shown. Sensor pixel 100 includes a substrate 101, conductive element 102, capacitive sensing electrode 110, and shield 120. Shield connector 122 is also shown. Although not explicitly shown in FIG2a, shield connector 122 is connected to one or more conductive elements, such as a reference voltage source (thereby electrically connecting shield 120 to the element, for example, to maintain shield at shield voltage).

[0037] The substrate 101 provides a base layer to the sensor pixel, and the remaining stacked plurality of layers are disposed on top of the base layer. A first conductive layer 105a is located below the second conductive layer 105b. The conductive element 102 is at least partially disposed in the first conductive layer 105a. The first conductive layer 105a may include a metallization layer. For example, the first conductive layer 105a may be formed from a region of conductive material, such as metal, deposited on top of a layer below it, such as on the substrate 101 itself.

[0038] The sensor pixel 100 may be configured such that the conductive element 102 (and any other plurality of conductive elements not shown in the figures) is disposed within a first region of the sensor pixel. The first region may be relatively small compared to the entire region of the sensor pixel 100. For example, the first region may occupy less than half of the total region of the sensor pixel. The conductive element 102 may include a thin-film transistor. It should be understood that in practice, the thin-film transistor may be disposed using two or more conductive layers, but for simplicity, only elements of conductive layers are shown here. The conductive element 102 may be configured to face the periphery of the sensor pixel. For example, the conductive element 102 may be located closer to the periphery (e.g., the circumference) of the sensor pixel 100 than closer to the center of the sensor pixel 100.

[0039] A shielding cover 120 and a capacitive sensing electrode 110 are disposed in a second conductive layer 105b. The second conductive layer 105b is located above the first conductive layer 105a. Although not shown, there is one or more layers, such as an intermediate insulating layer, between the first conductive layer 105a and the second conductive layer 105b. In the second conductive layer 105b, the shielding cover 120 and the capacitive sensing electrode 110 are separated from each other (e.g., they do not contact each other). The shielding cover 120 may occupy a small area of ​​the second conductive layer 105b relative to the capacitive sensing electrode 110. For example, the capacitive sensing electrode 110 may span a large portion of the second conductive layer 105b. The second conductive layer 105b may include a metallization layer. For example, the second conductive layer 105b may be formed from a region of conductive material, such as metal, deposited on top of a layer below it, such as on an insulating layer.

[0040] Shielding cover 120 covers conductive element 102. That is, shielding cover 120 is located above conductive element 102. There is one or more layers between shielding cover 120 and conductive element 102. Shielding cover 120 may cover all (or at least most) of the first region. In other words, conductive element 102 may be completely covered by shielding cover 120. For example, when viewed in a plane, the area occupied by conductive element 102 may fall completely within the area covered by shielding cover 120. It should be understood that although only conductive element 102 is shown in FIG. 2a, in examples where multiple conductive elements are present, these may all be covered by shielding cover 120 (e.g., they may all fall within the area covered by shielding cover 120). Capacitive sensing electrode 110 does not cover conductive element 102. For example, there may be no conductive element below capacitive sensing electrode 110, or at least any capacitive coupling between the conductive element below capacitive sensing electrode 110 and capacitive sensing electrode 110 may be ignored.

[0041] A shield 120 is disposed vertically above the conductive element 102 (e.g., when the sensor is upright and the second conductive layer 105b is above the first conductive layer 105a). The shield 120 may completely surround the lateral extent of the conductive element 102. The capacitive sensing electrode 110 may be laterally offset from the conductive element 102. There may be no lateral overlap between the capacitive sensing electrode 110 and the conductive element 102. For example, there may be no conductive element vertically below the capacitive sensing electrode 110.

[0042] It should be understood that one or more electrical connections may be provided for electrically connecting elements in the second conductive layer 105b to elements in the first conductive layer 105a. For example, each sensor pixel 100 may include one or more conductive vias to provide electrical connections between different conductive layers. Only one of these, namely the shield connector 122, is shown in FIG2a. Although not shown in FIG2a, the shield connector 122 electrically connects the shield 120 to one or more other conductive elements of the sensor to maintain the shield 120 at a shield voltage. For example, the shield connector 122 electrically connects the shield 120 to a reference voltage source. In FIG2a, the shield connector 122 is shown as extending from the sensor pixel 100 (on top of the substrate 101) to provide connection to a reference voltage source (although the reference voltage source is not shown in FIG2a). Any suitable electrical connection may be used to connect the shield 120 to the reference voltage source (and thus maintain the shield 120 at the reference voltage).

[0043] Sensor pixel 100 is configured to output a readout signal that can represent the amount of charge stored on capacitive sensing electrode 110. For this purpose, conductive element 102 outputs a readout signal that can represent the amount of charge stored on capacitive sensing electrode 110. The sensor can be configured to provide one or more electrical signals to sensor pixel 100 to cause sensor pixel 100 to output a readout signal. For example, the sensor can apply a scan signal to sensor pixel 100 and / or provide a supply voltage to sensor pixel. In response, sensor pixel 100 can be configured to output a readout signal.

[0044] The sensor is configured to maintain shield 120 at a reference voltage. Shield connector 122 is configured to electrically connect shield 120 to a reference voltage source. Shield 120 can therefore be maintained at a reference voltage associated with the reference voltage source. The sensor can be configured to selectively maintain shield 120 at the reference voltage. For example, the sensor can selectively connect shield 120 to a reference voltage source. The sensor is configured to connect shield 120 to the reference voltage source when sensor pixel 100 is activated and provides a readout signal therefrom.

[0045] The shield 120 is configured to be capacitively coupled to the conductive element 102. In other words, the shield 120 and the conductive element 102 can be equivalently configured to each provide a plate of a capacitor. (For example, where the two plates are separated by any intermediate layer, such as an insulating layer). It should be understood that, in the context of this disclosure, the shield 120 can be configured to be capacitively coupled to any suitable element (e.g., any part of the sensor pixel 100, which can store some charge and thus provide capacitive coupling). For simplicity, it is referred to herein as the conductive element 102, but the element can have additional or alternative electrical properties. The shield 120 will be maintained at its reference voltage, and the plates of the equivalent capacitor will be at a known reference voltage. When a readout signal is obtained from the sensor pixel, the shield 120 is maintained at the reference voltage, so the voltage of the shield 120 can be known over a period of time.

[0046] The capacitance sensing electrode 110 is positioned away from the conductive element 102 such that no (or minimal) capacitive coupling occurs between them. Instead, capacitive coupling will occur between the shield 120 and the conductive element. In other words, the sensor is configured to induce controlled (parasitic) capacitive coupling between the shield 120 and the conductive element 102. The controlled capacitive coupling of the shield 120 is selected to suppress parasitic capacitive coupling between the capacitance sensing electrode 110 and the conductive element 102 (or any other related element that may be under variable and unknown voltages, thus providing unknown parasitic effects).

[0047] In operation, sensor pixel 100 is activated to obtain a readout signal from it. In this example, activating sensor pixel 100 includes applying a scan signal to sensor pixel 100 to selectively turn on sensor pixel 100, and also providing sensor pixel 100 with a supply voltage for the sensor and then outputting a readout signal. Activating sensor pixel 100 also includes electrically connecting shield 120 to a reference voltage source. This causes shield 120 to be charged to a reference voltage associated with the reference voltage source (e.g., current can flow through shield connector 122, causing shield 120 to be at the reference voltage). Shield 120 will be capacitively coupled to conductive element 102, but capacitive sensing electrode 110 will not. If any capacitive coupling exists between capacitive sensing electrode 110 and shield 120, the effect of shield 120 on the coupling will be known because shield 120 remains at the reference voltage. The sensor pixel 100 outputs its readout signal for processing by the sensor's readout circuit, thereby determining the proximity of the object to be sensed to the capacitive sensing electrode 110.

[0048] Another example of a sensor pixel will now be described with reference to FIG2b.

[0049] FIG. 2b shows sensor pixel 100. The sensor pixel stack of sensor pixel 100 is shown as including three conductive layers: a first conductive layer 105a, a second conductive layer 105b, and a third conductive layer 105c. For simplicity, other conductive layers and any intermediate layers are not shown. Similar to FIG. 2a, the sensor pixel 100 of FIG. 2b includes a substrate 101, a conductive element 102, a capacitive sensing electrode 110, and a shield 120. The shield connector 122 is also shown in FIG. 2b.

[0050] The sensor pixel 100 in FIG2b is similar to that in FIG2a, except that in FIG2b, the shield 120 is disposed in a different conductive layer than the capacitive sensing electrode 110. The shield 120 is disposed in a conductive layer below the conductive layer in which the capacitive sensing electrode 110 is disposed. For this purpose, the shield 120 is disposed in a second conductive layer 105b, and the capacitive sensing electrode 110 is disposed in a third conductive layer 105c.

[0051] The capacitive sensing electrode 110 is located in the uppermost conductive layer of the sensor pixel. A shield 120 is located in a layer between the uppermost (third layer) and the lower (first layer), for example, the shield 120 is vertically located in a layer between the capacitive sensing electrode 110 and the conductive element 102. The shield 120 covers the conductive element 102. The configuration of the first conductive layer 105a does not need to be the same as that of FIG. 2a. For example, any conductive elements in the first conductive layer 105a may be spatially distributed over the entire area of ​​the sensor pixel, or they may only extend across the periphery of the area of ​​the sensor pixel. The shield 120 may extend across the area of ​​the sensor pixel 100, covering any conductive elements in the plurality of layers below it. In other words, the conductive element 102 may fall entirely within the lateral extent of the shield 120 (in the layers above it). For example, the shield 120 may extend across most of the second conductive layer 105b, for example, it may cover all of them. For example, and as described in more detail in the example below (and also applicable to the example shown in Figure 2a), the electrical shield 120 can span more than one sensor pixel.

[0052] The lateral extent of the shield 120 can cover a large portion of the area of ​​the sensor pixel covered by a plurality of conductive elements. For example, the lateral extent of the shield 120 can cover all conductive elements in the plurality of layers below it. The shield 120 may include one or more openings through which conductive connections between the capacitive sensing electrode 110 and other elements of the circuitry pass. For example, a conductive via can pass through an opening in the shield 120 to reach elements in the lower layer of the sensor pixel from the capacitive sensing electrode 110. The capacitive sensing electrode 110 covers the shield 120. There may be areas where the capacitive sensing electrode 110 is not present, such as (i) covering conductive elements 102 in the lower layer of the sensor pixel stack, and (ii) not covering the shield 120 (unless the area of ​​the capacitive sensing electrode 110 is electrically connected to the conductive elements 102, for example, through an opening in the shield 120). In other words, the shield 120 can completely isolate (spatially) the capacitive sensing electrode 110 from any conductive elements below the shield 120. The shield 120 may be the same size as, smaller than or larger than the capacitive sensing electrode 110. For example, the size of the shield 120 may be designed such that it covers all the conductive elements in the multiple layers beneath it.

[0053] Similar to the sensor pixel 100 of FIG. 2a, the shield 120 in the sensor pixel 100 of FIG. 2b is configured to be capacitively coupled to conductive elements in the plurality of layers beneath it. The shield 120 is capacitively coupled to the elements rather than capacitively coupled to the capacitive sensing electrode 110. When a read signal is received from the read pixel, the sensor pixel 100 is configured to maintain the shield 120 at a reference voltage. The shield 120 will be at a known reference voltage. The shield 120 is configured to suppress parasitic capacitive coupling between the capacitive sensing electrode 110 and any conductive elements in the plurality of layers beneath the shield 120. The sensor can be configured such that any parasitic capacitive coupling between the capacitive sensing electrode 110 and any other conductive element in the sensor pixel 100 becomes coupling between the capacitive sensing electrode 110 and the shield 120. When a read signal is received from the sensor pixel, the shield 120 remains at a fixed voltage, so the effect of any parasitic capacitive coupling between the shield 120 and the capacitive sensing electrode 110 can be known. Any effect that coupling may have on the stored charge on the capacitive sensing electrode 110 during readout can be parameterized in the measurement results. This effect can be determined when the shield 120 is at a known and fixed voltage. In other words, the sensor pixel 100 can be configured such that the shield 120 is the (primary) element of the sensor pixel 100, with which the capacitive sensing electrode 110 will be coupled.

[0054] The operation of sensor pixel 100 in FIG2b can be the same as that in FIG2a.

[0055] In the context of this disclosure, it will be understood that any arrangement of the sensor pixels 100 can provide electrical shielding for the capacitive sensing electrodes 110, and thus can improve the signal-to-noise ratio of the sensor. The arrangement of FIG2a can advantageously reduce the need for multiple conductive layers, while the capacitive coupling between the shield 120 and the capacitive sensing electrodes 110 may be less critical. The arrangement of FIG2b can advantageously reduce the constraints on the spatial layout of the individual conductive layers. The sensors disclosed herein may include multiple sensor pixels 100 of any one or both types.

[0056] Different examples of shielding will now be described with reference to Figures 3 to 5.

[0057] FIG3 shows a plan view of a portion of a sensor array 10 containing a plurality of sensor pixels 100. The boundaries of the sensor pixels 100 are indicated by dashed lines in FIG3. The portion shown in FIG3 is intended to illustrate the different relative arrangements of the shield 120 and the capacitive sensing electrode 110 of one or more sensor pixels 100 of the sensor array 10.

[0058] Figure 3 illustrates six examples of different configurations of the complex shield 120 and the complex capacitive sensing electrodes 110. Each example is intended to demonstrate different possible configurations of the shield and one or more capacitive sensing electrodes that will be shielded by the shield.

[0059] In the first example, there is a first capacitive sensing electrode 110a and a first shield 120a. In the first example, the sensor pixel 100 can be of the type shown in FIG. 2a. The sensor pixel 100 is configured so that there is no spatial overlap between the first shield 120a and the first capacitive sensing electrode 110a. The first shield 120a is disposed towards the periphery, for example, towards a corner of the sensor pixel. However, this is only an example, and the first shield 120a can alternatively be configured to extend across a larger area at the periphery of the sensor pixel 100. For example, it can extend across a strip along one or more sides (at the edge) of the sensor pixel, for example, it can be external to the first electrode 110a of the sensor pixel 100. The first capacitive sensing electrode 110a extends across most of the remaining area of ​​the sensor pixel 100 (which is also most of the total area of ​​the sensor pixel). Any conductive elements of the sensor pixel 100 can also be located in the area below the first shield 120a of the sensor pixel 100. The first shield 120a can be at least partially surrounded by an area without conductive material. The region can separate 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 should be understood that the first shield 120a can span two or more sensor pixels 100 (i.e., provide shielding for all sensor pixels 100). In either case, the first shield 120a can span only a sub-region of the region of each sensor pixel 100, leaving space for the first capacitive sensing electrode 110a of each sensor pixel 100 in the same conductive layer.

[0060] In each of the second, third, and sixth examples, different relative dimensions of the shield and the capacitive sensing electrode are represented. In each of these examples, the multiple sensor pixels 100 can be of the type shown in FIG. 2b. Thus, each capacitive sensing electrode can be disposed in a conductive layer in the pixel stack that is higher than the conductive layer in which the shield is disposed (i.e., the capacitive sensing electrode is located above the shield). As described above, each shield may include one or more openings for allowing electrical connections between (i) the capacitive sensing electrode in a layer above the shield and (ii) electronic components in one or more layers below the shield. In these three examples, each sensor pixel is represented as a shield. However, it should be understood that each shield may instead span two or more multiple sensor pixels 100 (e.g., providing shielding for multiple sensor pixels 100).

[0061] In the second example, the second shield 120b is smaller than the second capacitive sensing electrode 110b. The second shield 120b is indicated by a dashed line because it is located 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 can be completely contained 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 can completely circumvent and surround the area covered by the second shield 120b. Alternatively, the two areas can 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 position of the second shield 120b can be selected such that the second shield 120b covers any conductive elements in the plurality of lower layers of the sensor pixel 100 (therefore, the portions of the second shield 120b not covered by the second capacitive sensing electrodes 110b also do not cover any conductive elements that they can capacitively couple with).

[0062] In the third example, the third shield 120c and the third capacitive sensing electrode 110c are the same size (or at least the two regions can be substantially the same). The area covered by the third shield 120c can be the same as the area covered by the third capacitive sensing electrode 110c, and these two regions may not completely overlap.

[0063] 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 surround the area covered by the sixth capacitive sensing electrode 110f. Alternatively, one or more portions of the sixth capacitive sensing electrode 110f may not cover the sixth shield 120f. The sensor pixel 100 may be configured such that portions of it also do not cover any conductive elements of the sensor pixel 100 that can be capacitively coupled.

[0064] In the fourth and fifth examples, a shield spans a plurality of sensor pixels 100.

[0065] In the fourth example, a fourth shield 120d spans a plurality of sensor pixels 100 and their associated plurality of fourth capacitive sensing electrodes 110d. The fourth shield 120d is used for each sensor pixel 100 in a column. The fourth shield 120d can be configured to cover each of the plurality of sensor pixels 100, wherein the fourth capacitive sensing electrode 110d of the sensor pixel 100 will not have a plurality of conductive elements in the plurality of underlying layers that are capacitively coupled to the electrode 110d but are not covered by the fourth shield 120d. The fourth shield 120d can cover all or most of each of the fourth capacitive sensing electrodes 110d in a column. For example, the area covered by each of the fourth capacitive sensing electrodes 110d in a row can fall within the area covered by the fourth shield 120d. In other words, a conductive element can provide shielding for each of the plurality of sensor pixels 100, for example, for each sensor pixel 100 in a column of array 10.

[0066] In the fifth example, the fifth shield 120e spans a plurality of sensor pixels 100 and their associated plurality of fifth capacitive sensing electrodes 110e. The fifth shield 120e can be the same as the fourth shield 120d, except that the fifth shield 120e spans more than one column of the plurality of sensor pixels 100. As shown, the fifth shield 120e does not need to be used for all the plurality of sensor pixels 100 in each column. Alternatively, although not shown in FIG. 3, but described later with reference to FIG. 5, the fifth shield 120e can be used for each sensor pixel 100 in the array 10. For example, the shield can be configured to suppress parasitic coupling between each capacitive sensing electrode of the array 10 and any other conductive element within the array 10 that can be capacitively coupled to each capacitive sensing electrode.

[0067] Another example of an array of complex sensor pixels will now be described with reference to Figures 4a and 4b.

[0068] Figure 4a shows a portion of an array 10 of complex sensor pixels 100. Figure 4a shows the array 10 without any shielding cover 120 or any shielding connector 122, but these are shown in Figure 4b. Two columns and three rows of complex sensor pixels 100 are shown in the array 10, but it should be understood that this is only a portion of the array 10, and more complex columns and rows can be provided. Each sensor pixel represents a capacitive sensing electrode 110. The sensor array 10 represents a complex number of conductive lines. These include: a complex number of scan lines 131, a complex number of supply lines 132, and a complex number of readout lines 133. Solid black circles are used to indicate the electrical connections between the complex sensor pixels 100 and the associated complex conductive lines.

[0069] Each sensor pixel 100 in array 10 can be connected to a plurality of conductive lines. Specifically, each sensor pixel 100 can be connected to scan lines 131, supply lines 132, and readout lines 133. Each scan line 131 can be associated with a plurality of sensor pixels 100 in a corresponding column. That is, each scan line 131 is connected to all the plurality of sensor pixels 100 in its column. Each column of plurality of sensor pixels 100 has an associated scan line 131. Each supply line 132 can be associated with a plurality of sensor pixels 100 in a corresponding row. That is, each supply line 132 can be connected to all the plurality of sensor pixels 100 in its row. Each row of plurality of sensor pixels 100 has an associated supply line 132. Each readout line 133 can be associated with a plurality of sensor pixels 100 in a corresponding row. That is, each readout line 133 is connected to all the plurality of sensor pixels 100 in its row. Each of the rows of the complex sensor pixels 100 has an associated scan line 131.

[0070] To activate a sensor pixel, the sensor is configured to apply a scan signal to sensor pixel 100 (via scan line 131 connected to the sensor pixel). The scan signal may be in the form of a voltage signal. For example, the sensor may be configured to selectively connect scan line 131 to a voltage source to apply a scan signal to scan line 131. The sensor may be configured to apply a scan signal to each sensor pixel 100 in a column (which is connected to scan line 131). Furthermore, to activate a sensor pixel, the sensor is configured to apply a supply signal to sensor pixel 100 (via 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 supply line 132 to a supply voltage source to apply a supply voltage to the sensor pixel. The sensor may be configured to apply a supply voltage to each sensor pixel 100 in a row.

[0071] The activated sensor pixel 100 may be a sensor pixel 100 that receives a scan signal (from a scan line 131 connected thereto) and is supplied with a supply voltage (from a supply line 132 connected thereto). The activated sensor pixel 100 is configured to output a readout signal (to its connected readout line 133). The readout signal represents the amount of charge stored on the capacitive sensing electrode 110. This can, in turn, provide an indication of the proximity of a conductive object to be sensed to the capacitive sensing electrode 110. Each readout line 133 may be connected to a processing channel of a readout processing circuit, the processing channel being configured to process multiple readout signals from the readout line 133.

[0072] The sensor is configured to selectively apply scan signals and supply voltages to different plurality of sensor pixels 100 to selectively activate each sensor pixel 100. Specifically, the sensor may be configured to apply a scan signal to one scan line 131 at a time. The scan signal may charge the scan line 131 to a selected voltage (e.g., a voltage associated with a voltage source connected to the scan line 131). The sensor may also be configured to apply a supply voltage to one or more supply lines 132. (i) In one of the supply lines 132, and (ii) each sensor pixel 100 in the column connected to the scan line 131 will be activated. A plurality of readout signals will be output from the sensor pixels 100 to readout lines 133 connected to the activated pixels 100.

[0073] In other words, the sensor can be configured to apply a scan signal (e.g., a fixed voltage) to all sensor pixels 100 in a column of the array 10 at a time. The remaining multiple columns of the sensor array 10 may not be activated. That is, their multiple scan lines 131 may not be charged to the scan voltage. When one or more readout signals are obtained from any activated multiple sensor pixels 100 in a column, the scan line 131 of the column will be at the scan voltage. The sensor pixels 100 that output multiple readout signals within a column may only be those connected to the activated multiple supply lines.

[0074] As will now be described with reference to FIG4b, when a complex readout signal is obtained from the complex capacitive sensing electrode 110 associated with the shield 120, this setting can be used to selectively maintain the complex shield 120 of the sensor pixel at the shield voltage.

[0075] FIG4b shows the same sensor array 10 as shown in FIG4a. FIG4b also shows the sensor array 10 having a plurality of shields 120 and a plurality of shield connectors 122.

[0076] Each column of multiple sensor pixels 100 has an associated shield 120. That is, a shield 120 is provided for all sensor pixels 100 in a column. A separate shield 120 is provided for the multiple sensor pixels 100 in each column. The shield 120 of each column is configured to provide electrical shielding of the type described herein for all capacitive sensing electrodes 110 in its column. That is, for each column, each capacitive sensing electrode 110 in the column is shielded by a shield 120 of the column. The shield 120 of each column is connected to a scan line 131 associated with the column. As shown in FIG4b, a shield connector 122 may be provided for each shield 120, wherein the shield connector 122 electrically connects the shield 120 of a column to the scan line 131 of the column.

[0077] The sensor is configured such that the voltage to be supplied to the sensor pixels 100 in a column (e.g., the scan voltage used to activate at least one of the sensor pixels 100) is also supplied to the column's shield 120. In other words, the sensor is configured such that activating a plurality of sensor pixels 100 in a column also charges the row's shield 120 to a selected voltage (i.e., to the scan voltage). With this configuration, the plurality of sensor pixels may not be activated if the shields of the plurality of sensor pixels are not charged to a fixed (and known) voltage. In this example, the shield voltage for the shield 120 would be the scan voltage applied to the scan line 131 to activate the plurality of sensor pixels 100. The sensor is configured such that when a sensor pixel 100 is activated (i.e., when a scan signal is applied to the sensor pixel), the selected voltage (i.e., the scan voltage) is also applied to the shield 120, and therefore, when a readout signal is obtained from the activated sensor pixel, the sensor is configured to maintain the shield 120 at the selected voltage.

[0078] In operation, the sensor addresses one column at a time. For the first column, a scan signal is applied to the scan line 131 of the column, and a supply voltage is provided to some or all of the supply lines 132 of different rows having a plurality of pixels 100 in the column. Activated pixels 100 in the column will receive: (i) the scan signal from their scan line 131, and (ii) the supply voltage from their supply lines 132. Each activated pixel 100 then outputs a readout signal to its readout line 133 for processing by the sensor's readout circuitry.

[0079] While the scan signal is applied to the sensor pixel 100 in the row via the column scan line 131, the same scan signal is also applied to the column shield 120. The shield 120 will therefore be charged to the scan voltage. The voltage of the shield 120 may change (i.e., increase or decrease) for an initial period, such that it subsequently reaches the scan voltage. However, it should be understood that this will happen quickly in practice. For the remaining duration while the scan signal is applied to the scan line 131 (and during which time the plurality of pixels 100 in the column can be activated to output readout signals), the shield 120 will remain at the scan voltage.

[0080] Thus, when a readout signal indicating the amount of charge stored on the capacitive sensing electrode 110 is obtained, the shield 120 will be at a fixed voltage. Any capacitive coupling that occurs between the shield 120 and the capacitive sensing electrode 110 will therefore occur when one of the equivalent plates of the capacitor is held at a fixed, constant, and known voltage (i.e., the scan voltage). Therefore, any effect of such capacitive coupling is known because the voltage of one of the capacitor plates is known, while the other plate provides the parameter to be measured (i.e., the amount of charge stored on the plate). At the same time, since the shield 120 is provided to shield the capacitive sensing electrode 110, less parasitic capacitive coupling can occur between the capacitive sensing electrode 110 and the other multiple conductive elements of its sensor pixel. Therefore, by fixing the shield 120 to a known voltage, the measurement results obtained from the sensor array 10 can contain less noise from unknown sources.

[0081] The method can then continue by activating different subsets of the sensor pixels 100 in the activation array 10. After the multiple pixels 100 activated in the first column have output multiple readout signals to their respective multiple readout lines 133, the sensor can apply a scan signal to the subsequent scan line 131. For example, the sensor can address the multiple sensor pixels 100 row by row. Once the multiple sensor pixels 100 activated in the first column have output multiple readout signals, the multiple sensor pixels 100 in the second column can be activated. This procedure can be repeated for each column in the sensor array 10. This procedure can be repeated several times for each column, such that each time a column is addressed, a first subset of the sensor pixels 100 in the column outputs multiple readout signals, and then the next time a column is addressed, a different subset of the multiple sensor pixels 100 in the column outputs multiple readout signals. By iterating this process, each sensor pixel 100 (or at least the majority, such as most) in the array 100 can output and process at least one readout signal. In each step of this method, when a specific subset of the sensor pixels 100 in the array 10 is activated, the shields 120 of those activated sensor pixels 100 will be maintained at the scan voltage (because the same scan signal that activates those sensor pixels 100 will also be applied to the shields 120 of those activated sensor pixels 100).

[0082] Another example of a sensor array is shown in Figure 5.

[0083] FIG5 shows a sensor array 10 containing a plurality of sensor pixels 100. The boundaries of the sensor pixels 100 are shown by dashed lines. FIG5 also shows the capacitive sensing electrode 110 and shield 120 of each sensor pixel 100. In the example of FIG5, the shield 120 covers the entire sensor array 10. In other words, each sensor pixel 100 has a shield 120 disposed of by the same single conductive element.

[0084] Figure 5 also shows the voltage source 124 and the interference protection circuit 140. The interference protection circuit 140 may include a plurality of diodes for connecting the shield 120 to the voltage rails of the sensor. Illustration A of Figure 5 shows the interference protection circuit 140 having a first voltage rail 141 (e.g., a high voltage rail) and a second voltage rail 142 (e.g., a low voltage rail). The circuit shown in illustration A also includes a high diode 141a and a low diode 142a.

[0085] The shield 120 spans the entire sensor array 10, providing electrical shielding for each capacitive sensing electrode 110 in the array 10. For example, the shield 120 may be configured as a conductive layer covering the entire (or at least most) area of ​​the sensor array 10. The sensor of FIG5 may be configured to operate in the same manner as the sensors described above; for example, the sensor pixel 100 may be activated by receiving a scan signal on its scan line and a supply voltage on its supply line. In FIG5, one connection between the shield 120 and the voltage source 124 is shown. However, multiple such connections may exist.

[0086] Voltage source 124 may be a controlled voltage source, such as a voltage source configured to set the shield 120 to a selected voltage. The controlled voltage source 124 is configured to control the voltage of the shield 120 such that when multiple readout signals are obtained from the activated multiple pixels 100, the selected voltage (i.e., the shield voltage) is a constant voltage. Voltage source 124 may be provided by another voltage source used within the sensor, such as a voltage source for scanning signals or a supply voltage source. As another example, voltage source 124 may be electrically grounded; for example, the connection of the shield 120 to electrical ground grounds any voltage it carries (e.g., to 0 volts). Voltage source 124 may be a separate voltage source. For example, it may be a voltage source specifically for the shield 120.

[0087] In an example where the voltage source 124 is also used to provide voltage to other elements of the sensor, such as when the voltage source 124 provides a scan voltage or supply voltage to a plurality of sensor pixels 100, the shield 120 may have a plurality of 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 scan voltage source such that whenever a scan voltage is applied to any of the sensor array 10, the scan voltage is also provided to the shield 120 via the electrical connection.

[0088] Similarly, if the shield 120 is electrically connected to receive the supply voltage, the shield 120 may be connected to each supply line in the sensor array 10. Alternatively, the shield 120 may be connected to only some of the supply lines, but in selecting these supply lines, the shield 120 will receive the supply voltage for each activated pixel. For example, to activate multiple sensor pixels 100, multiple supply lines can be activated simultaneously at any time, so the shield 120 may only need to be connected to some of the supply lines so that it always receives the supply voltage when multiple sensor pixels 100 are activated. Alternatively or additionally, a direct electrical connection may exist between the shield 120 and the supply voltage source, such that whenever a supply voltage is applied to any of the rows in the sensor array 10, the supply voltage is also supplied to the shield 120 via the direct connection.

[0089] In any of these examples, when a plurality of readout signals are obtained from the plurality of sensor pixels 100 activated within the array 10, the sensor is configured such that the shield 120 will maintain its shielding voltage. It should be understood that since the shield 120 covers all the capacitive sensing electrodes 110 of the sensor array 10, any subset of the plurality of sensor pixels 100 within the array 10 can be activated at any time and a single shield 120 will still provide electrical shielding for those sensor pixels 100.

[0090] As described above, the sensor can be operated by activating a plurality of sensor pixels 100 in a first column, and then activating a plurality of sensor pixels 100 in subsequent columns, until a plurality of readout signals have been obtained from the required number / proportion of sensor pixels 100 in the array 10. For example, the procedure can be repeated iteratively until a readout signal is obtained from each sensor pixel. Each time a readout signal is obtained from an activated sensor pixel, the shield 120 will be maintained at its shield voltage. It should be understood that, in the context of this disclosure, each subsequent activation of the plurality of sensor pixels 100 can occur very rapidly, for example, making it possible to obtain a plurality of readout signals from all sensor pixels 100 within a relatively short period of time. One advantage of using a single shield 120 for all sensor pixels 100 in the array 10 is that it is less necessary to charge / discharge the shield 120 to the shield voltage between subsequent sensor pixel activations. For example, when a sensor pixel completes startup, the shield 120 will be at the shield voltage, and the next sensor pixel startup will occur shortly thereafter. Thus, the shield voltage is unlikely to change significantly between the end of one sensor pixel startup and the start of the next. This can reduce the total power consumption required to power the sensor.

[0091] In the examples described herein, one or more shields 120 are included to provide electrical shielding for the capacitive sensing electrode 110 to prevent parasitic coupling with other elements of the sensor. These include, for example, other multiple conductive elements within the sensor (e.g., electronic components of the sensor pixel 100 and / or wiring for providing electrical connections to the sensor pixel). The shields disclosed herein may have additional characteristics that contribute to improved sensor operation. Although the following examples will be described primarily with reference to the shield 120 of FIG. 5, it should be understood that they can also be applied to any of the shields 120 disclosed herein.

[0092] In some examples, the shield 120 may be configured to provide interference protection. Specifically, the shield 120 may be configured to provide protection against unintended electrical effects, such as electrostatic discharge and / or electromagnetic interference. For this purpose, the sensor may also include an interference protection circuit 140 of the type shown in FIG. 5. The interference protection circuit is configured to selectively provide a conductive path away from the shield 120 for offsets exceeding a threshold. For example, if the voltage of the shield 120 is greater than an upper threshold voltage or less than a lower threshold voltage (e.g., a negative threshold voltage), the protection circuit 140 is configured to divert excess current from the shield 120.

[0093] As shown in illustration A of FIG5, the interference protection circuit 140 may be formed by one or more diodes connecting the shield 120 to a first voltage rail (e.g., a high voltage rail) 141 and one or more diodes connecting the shield 120 to a second voltage rail (e.g., a 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 illustration 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 connected in series to connect the shield 120 to the high voltage / low voltage rails respectively.

[0094] Interference protection circuit 140 is configured to provide a conductive path away from shield 120. A high-voltage diode 141a provides the conductive path between shield 120 and high-voltage rail 141. If the voltage of shield 120 exceeds a threshold voltage (e.g., if the shield voltage is greater than the voltage of the high-voltage rail), current can flow from shield 120 and through high-voltage diode 141a to high-voltage rail 141. Similarly, a low-voltage diode 142a provides the conductive path between low-voltage rail 142 and shield 120 to divert current and suppress the voltage of shield 120 from falling below a threshold voltage (e.g., if the voltage of shield 120 is too negative).

[0095] In other words, the sensor can be configured to provide electrical protection for the sensor and any of its electronic components using the shielding 120 and the interference protection circuit 140. For example, the sensor can be configured to protect the sensor from electrostatic discharge and / or electromagnetic interference using the shielding 120 and the interference protection circuit 140.

[0096] 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 configured to provide optical shielding for the elements beneath it. When the plurality of sensor pixels 100 contain one or more thin-film transistors, the (plural) shield 120 of the sensor may be configured to cover these elements, and specifically cover the channel regions of the thin-film transistors. In addition to providing electrical shielding against capacitive coupling between the capacitive sensing electrodes 110 and the thin-film transistors, this configuration may also improve the operating characteristics of the thin-film transistors if the shield 120 is opaque (e.g., opaque to visible light). For example, certain performance characteristics may be affected by incident light on the thin-film transistors. That is, the operation of the thin-film transistors may change in response to incident light and / or the thin-film transistors may degrade over time with continuous exposure to ambient light. In other words, the shield 120 may provide optical protection for the sensor, for example, to protect the plurality of elements beneath the shield 120 from incident light. The incident light can be visible light and / or ultraviolet light (and / or electromagnetic radiation in other parts of the electromagnetic spectrum).

[0097] In some examples, the shield 120 can be configured to facilitate touch sensing operation. For example, the shield 120 can be used to detect touch sensing. This can be particularly useful when the (plural) shields 120 cover a large area 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 individual columns / rows. The capacitive sensing electrodes 110 can be configured with sufficiently high spatial resolution to facilitate biometric scanning, for example, enabling sufficiently high spatial resolution data for objects touching the sensors to be obtained, thereby enabling biometric identification from them, such as based on the acquired fingerprint data. The sensors can also be configured to operate in touch sensing mode. In touch sensing mode, the sensors can be configured to identify objects interacting with (e.g., touching) the sensors. For this purpose, the sensors can be configured to use the (plural) shields 120 of the sensor array 10. For example, in this context, using (plural) shields 120 of the sensor to detect contact can be an alternative to or supplement to using the capacitive sensing electrode 110.

[0098] The sensor can be configured to operate in two different modes: (i) a first mode, wherein the shield 120 is used for capacitive sensing, and (ii) a second mode, wherein the capacitive sensing electrode 110 is used for capacitive sensing. The first mode can be used for contact sensing (e.g., detecting a contact indication from an object with the sensor). The second mode can be used for capacitive biometric skin contact sensing. The sensor can be configured to initially operate in the first mode until a contact indication is sensed, and then switch to operating in the second mode. For example, the controller can be configured to sense contact in the first mode and, upon sensing a contact indication, switch to the second mode to perform higher spatial resolution sensing (e.g., performing capacitive biometric skin contact sensing on an object with a contact sensor).

[0099] Many different paradigms of (complex) sensors have been described herein, but it should be understood that these paradigms should not be considered limiting. Additional or alternative configurations may be provided. For example, reference is generally made to using shield 120 to suppress capacitive coupling between the capacitive sensing electrode 110 of the sensor and the complex conductive elements (e.g., conductive element 102). It should be understood that shield 120 is configured to preferentially capacitively couple with parasitic capacitance. For example, of any capacitive coupling from elements of sensor pixel 100, the coupling between those elements and shield 120 may be preferential over the coupling between those elements and capacitive sensing electrode 110. However, shield 120 may not completely eliminate all parasitic capacitive coupling with capacitive sensing electrode 110. Some parasitic coupling with capacitive sensing electrode 110 may still exist, but shield 120 is configured to attempt to minimize the amount of such residual coupling.

[0100] Moreover, reference is generally made to parasitic coupling with conductive element 102. It should be understood that, in the context of this disclosure, a plurality of different capacitive coupling sources may exist, for example, comprising one or more thin-film transistors, conductive lines, capacitors, etc. disposed on sensor pixel 100 and spanning sensor array 10. (A plurality of) shields 120 are configured to minimize the number of parasitic couplings originating from any potential parasitic coupling source to capacitive sensing electrode 110. For example, the sensor may be configured such that shield 120 preferentially capacitively couples with all such parasitic sources, for example, shield 120 may cover all such elements. Moreover, as will be understood, these elements may include any associated elements of the sensor that are capacitively coupled to capacitive sensing electrode 110. In other examples, the sensor may provide sensing in a different form than capacitive sensing. For example, each sensor pixel 100 may include a sensing element (instead of capacitive sensing electrode 110), such as an optical sensor detector, and the sensor may be configured to provide shielding of the sensing element from other elements of the sensor.

[0101] It should be understood that the shielding voltage can be any suitable voltage. The shield 120 is an "active shield," meaning that when the shielding capacitor sensing electrode 110 is shielded, the shield 120 will be actively connected to suitable elements to maintain the shield 120 at the shielding voltage (e.g., the shield 120 will not merely float). The shielding voltage can be positive or zero. The shield 120 can be connected to one or more conductive lines of the sensor array 10 to set the shield 120 to its fixed shielding voltage. For example, when the shielding voltage is positive, the shield 120 can be connected to a positive voltage source (e.g., a scan line or supply line), while when the shielding voltage is zero, the shield 120 can be connected to ground voltage (e.g., a ground wire connected to the ground of the sensor). The shield 120 can alternatively be connected to a separate voltage source or other suitable voltage source to maintain the shield 120 at the shielding voltage. The shield 120 can be connected to multiple conductive lines, such as multiple scan lines and / or multiple supply lines. The shield 120 can be permanently maintained at the shielding voltage (e.g., rather than selectively connected to a reference voltage source when the complex sensor pixels 100 are activated). Alternatively, in the example described above, a shield 120 can be provided for each column of complex sensor pixels 100. Alternatively, a shield 120 can be provided for each row of complex sensor pixels 100, for example, where each shield 120 is connected to the supply line of its row, such that the shield 120 is charged to the supply voltage for shielding.

[0102] It should be understood from the above discussion that the examples shown in the accompanying drawings are merely exemplary and contain features that can be generalized, removed, or replaced, as described herein and set forth in the claims. Referring generally to the accompanying drawings, it should be understood that the functional block diagrams are used to represent the functions of the systems and apparatuses described herein. Additionally, processing functions may also be provided by devices supported by electronic equipment. However, it should be understood that functions do not need to be divided in this way and should not be construed as implying any particular hardware structure other than those described below and claimed. The functions of one or more elements shown in the accompanying drawings may be further subdivided and / or distributed throughout the apparatus disclosed herein. In some examples, the functions of one or more elements shown in the accompanying drawings may be integrated into a single functional unit.

[0103] As those skilled in the art will understand in the context of this disclosure, each paradigm described herein can 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 features described in the operation of a particular element of an apparatus may be provided in a method that does not use those particular types of apparatus. Furthermore, features of each paradigm are intended to be separate from the features described in conjunction with them, unless it is expressly stated that certain other features are necessary for their operation. Each of these separable features may, of course, be combined with any other feature of the paradigm in which it is described, or with any other feature or combination of features of any other paradigm described herein. Moreover, equivalents and modifications not described above may be employed without departing from this disclosure.

[0104] Certain features of the methods described herein can be implemented in hardware, and one or more functions of the apparatus can be implemented in the method steps. It should also be understood that, in the context of this disclosure, the methods described herein need not be performed in the order they are described, nor necessarily in the order they are depicted in the accompanying drawings. Therefore, aspects of this disclosure described with reference to the articles or apparatus are also intended as method implementations, and vice versa. The methods described herein can be implemented as computer programs or in hardware or any combination thereof. Computer programs include software, middleware, firmware, and any combination thereof. Such programs can be configured as signals or network messages and can be recorded on computer-readable media, such as tangible computer-readable media that can store computer programs in a non-transitory form. Hardware includes computers, handheld devices, programmable processors, general-purpose processors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and gate arrays.

[0105] Other paradigms and variations will be apparent to those skilled in the art in the context of this disclosure. [Simplified Explanation of the Diagram]

[0018] Some examples disclosed herein will now be described by way of example only through reference diagrams, wherein:

[0019] Figure 1 is a schematic diagram of the complex sensor pixels of the capacitive sensor array.

[0020] Figure 2a is a cross-sectional view of the sensor pixel.

[0021] Figure 2b is a cross-sectional view of the sensor pixel.

[0022] Figure 3 is a schematic diagram of the complex sensor pixels of the capacitive sensor array.

[0023] Figure 4a is a schematic diagram of the complex sensor pixels of the capacitive sensor array.

[0024] Figure 4b is a schematic diagram of the complex sensor pixels of the capacitive sensor array.

[0025] Figure 5 is a schematic diagram of the complex sensor pixels of the capacitive sensor array.

[0026] In the diagram, similar symbols are used to represent similar elements.

Claims

1. A capacitive sensor, comprising an array of a plurality of sensor pixels, each sensor pixel comprising: A capacitive sensing electrode; and a conductive shield configured to electrically shield the capacitive sensing electrode from parasitic coupling with other elements of the sensor; wherein the sensor is configured to maintain the shield at a shielding voltage when a readout signal is obtained from the sensor pixel.

2. The sensor as claimed in claim 1, wherein the sensor further comprises: A plurality of conductive lines cross the array; and the shield is connected to at least one of the conductive lines.

3. The sensor as claimed in claim 2, wherein the at least one conductive line electrically connects the shield to a control voltage source.

4. The sensor as claimed in claim 3, wherein the at least one conductive line further comprises: One or more scan lines; one or more ground lines; or one or more voltage supply lines.

5. The sensor as claimed in any one of claims 1 to 4, wherein the shield covers the other elements of the sensor.

6. The sensor as claimed in any one of claims 1 to 4, wherein the shield and the capacitive sensing electrode are located on the same layer.

7. The sensor as claimed in any one of claims 1 to 4, wherein the shield is located as a layer between the capacitive sensing electrode and the other elements of the sensor.

8. The sensor as claimed in claim 7, wherein the capacitive sensing electrode covers the shield.

9. The sensor as claimed in any one of claims 1 to 4, wherein a single conductive element provides the shield for a plurality of sensor pixels.

10. The sensor as claimed in claim 9, wherein the single conductive element provides the shielding for all of the sensor pixels in the array.

11. The sensor as claimed in claim 10, wherein the single conductive element is connected to a plurality of conductive lines across the array.

12. The sensor as claimed in claim 9, wherein the single conductive element provides the shield for all of the sensor pixels in a column, and wherein the shield is connected to a scan line of the column.

13. The sensor as claimed in any one of claims 1 to 4, wherein the sensor is configured to operate in a first mode in which the shield is used to perform capacitive contact sensing.

14. The sensor of claim 13, wherein when operating in the first mode, it responds to receiving a contact indication, the sensor being configured to switch operation to a second mode in which the capacitive sensing electrode is used to perform capacitive biometric skin contact sensing.

15. The sensor as claimed in any one of claims 1 to 4, wherein the shield of each sensor pixel is substantially opaque to visible light and / or ultraviolet light.

16. The sensor as claimed in any one of claims 1 to 4, wherein the shielding of each sensor pixel is configured to shield against electromagnetic waves and / or electrostatic interference.

17. The sensor as claimed in claim 16, wherein the shield is coupled to a high-voltage rail and a low-voltage rail by means of one or more diodes configured to provide protection against electrical interference.

18. The sensor as claimed in any one of claims 1 to 4, wherein the circuitry of the sensor pixels further comprises: At least one thin film transistor (TFT); wherein the shielding is configured to electrically shield the parasitic coupling between the capacitive sensing electrode and the TFT.

19. A capacitive sensing method using an array of complex sensor pixels, each sensor pixel comprising: A capacitive sensing electrode; The method includes: a conductive shield configured to electrically shield the capacitive sensing electrode from parasitic coupling to other elements of a sensor; and the method further includes: maintaining the shield at a shielding voltage to provide electrical shielding of one of the capacitive sensing electrodes when a readout signal is obtained from the sensor pixel.

20. The method of claim 19, wherein the shield is connected to a control voltage source to maintain the shield at the shielding voltage.

21. The method of claim 20, wherein the shield is connected to the control voltage source via one or more conductive lines across the array.

22. The method of claim 21, wherein the shield is connected to: one or more scan lines; one or more ground lines; or one or more voltage supply lines to connect the shield to the control voltage source, and the shield is maintained at the shield voltage when the readout signal is obtained from the sensor pixel.

23. The method as described in any one of claims 19 to 22, further comprising: The shield is used to obtain a contact indication with the array, and upon detection of the contact indication, the capacitive sensing electrodes are used to perform biometric sensing.

24. The method of any one of claims 19 to 22, wherein the method comprises: At the same time, the shielding cover of the multiple sensor pixels is maintained at the shielding voltage.

25. A computer program product comprising a plurality of computer program instructions configured to control a capacitive biometric skin contact sensor to execute any one of requests 19 to 24.

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