Capacitive sensor

Abstract

The present invention provides a capacitive sensor, including a first electrode and at least one second electrode. The first electrode includes at least one opening. The at least one second electrode covers the at least one opening of the first electrode.

Description

Technical Field

[0001] This invention relates to electronic devices, and more particularly to capacitive sensors that utilize stray capacitance sensing. Background Technology

[0002] The two main capacitive sensing methods are self-capacitance sensing and mutual capacitance sensing. Self-capacitance sensing may be a good solution for fingerprint sensing because a large capacitance (signal) change is expected due to the vertical electric field, but it requires a capacitance-to-voltage conversion for sensing. On the other hand, mutual capacitance sensing has a voltage output, which simplifies circuit design, but no large capacitance (signal) change is expected due to the lateral electric field of fingerprint sensing.

[0003] Furthermore, self-capacitance sensing has a capacitance-to-voltage converter within the pixel, which is a hurdle for high dots per inch (dpi) displays. Another approach is to use a converter that transfers charge from the capacitor to the fingerprint (ridge or valley) outside the display area via sensing lines. The capacitive load on the sensing lines slows down the scanning speed and reduces noise immunity. Summary of the Invention

[0004] To address the aforementioned problems, this disclosure provides an electronic device suitable for sensing fingerprints. The capacitive sensor includes a first electrode and at least one second electrode. The first electrode includes at least one opening. The at least one second electrode is disposed on the first electrode. The at least one second electrode covers at least one opening of the first electrode. Attached Figure Description

[0005] A more complete understanding of this disclosure can be obtained by referring to the accompanying drawings and the following description of embodiments. It should be understood that these drawings are not drawn to scale according to standard industry practice. In fact, for clarity, this disclosure allows for arbitrary scaling of components. This means that many specific details, relationships, and methods are disclosed to provide a complete understanding of the disclosure.

[0006] Figure 1 This is a schematic diagram of a sensor pixel array having scan lines in rows and sensing lines in columns, according to an embodiment of the present disclosure.

[0007] Figure 2 Embodiments of this disclosure Figure 1 A top view of a capacitive sensor in the sensor pixel array.

[0008] Figure 3A Embodiments of this disclosure Figure 2 A schematic diagram of a capacitive sensor that interacts with fingerprints.

[0009] Figure 3B Embodiments of this disclosure Figure 3AThe equivalent circuit diagram of the capacitive sensor in the image.

[0010] Figure 4A This is a schematic diagram of a capacitive sensor that interacts with a fingerprint according to an embodiment of this disclosure.

[0011] Figure 4B Embodiments of this disclosure Figure 4A The equivalent circuit diagram of the capacitive sensor in the image.

[0012] Figure 1-4B The annotations in the accompanying drawings are explained as follows:

[0013] (m-1,n-1), (m,n-1), (m+1,n-1): Capacitive sensors

[0014] (m-1,n), (m,n), (m+1,n): Capacitive sensors

[0015] (m-1,n+1), (m,n+1), (m+1,n+1): Capacitive sensors

[0016] SSL(m-1), SLL(m), SLL(m+1): Sensing lines

[0017] SL(n-1), SL(n), SL(n+1): Scan lines

[0018] 200, 202: Electrodes

[0019] 210: Opening

[0020] 300: Conductive layer

[0021] 302: Fingerprint

[0022] 304: Common Electrode

[0023] 310, 312, 314: Insulation layer

[0024] Cts, Crs, Ctr, Cf: Capacitors

[0025] 320: Control Circuit

[0026] 330: Voltage Readout Circuit

[0027] 322, 324, 326, 332: Transistors

[0028] 334: Analog-to-Digital Converter

[0029] Vrx(m,n): Output voltage

[0030] Vtx: Sensing signal

[0031] Vr: Voltage

[0032] Reset: Reset signal

[0033] 400: Conductive layer

[0034] 402, 404, 406: Electrodes

[0035] 408, 410: Common electrode

[0036] 420: Fingerprint

[0037] 430, 432, 434: Insulation layer

[0038] Cts', Crs', Cfs', Ctf', Cfr', Cf': Capacitors

[0039] 440: Control Circuit

[0040] 442, 444, 446, 452: Transistors

[0041] 450: Voltage Readout Circuit

[0042] 454: Analog-to-Digital Converter Detailed Implementation

[0043] To make the objectives, features and advantages of some embodiments of this disclosure more readily understood, a detailed description is provided below in conjunction with the accompanying drawings.

[0044] Certain terms used throughout this specification and the following claims refer to specific components. Those skilled in the art will understand that electronic device manufacturers may use different names to refer to a component. This specification is not intended to distinguish between components with different names but different functions. It should be understood that the words "comprising," "having," and "including" are used in an open-ended manner and should therefore be interpreted as "including but not limited to...". Therefore, the terms "comprising," "having," and / or "including" as used in this disclosure are used to indicate the presence of specific technical features, values, method steps, operations, units, and / or components. However, this disclosure does not preclude the possibility of adding further technical features, values, method steps, workflows, units, components, or any combination thereof.

[0045] Directional terms used throughout this specification and the following claims, such as "upper," "above," "lower," "below," "front," "back," "left," and "right," are merely for reference to the accompanying drawings. Therefore, directional terms are used for interpretation only and not for limiting this disclosure. Regarding the drawings, they illustrate general features of methods, structures, and / or materials used in specific embodiments. However, the drawings should not be construed as identifying or limiting the scope or characteristics covered by these embodiments. For example, for clarity, the relative dimensions, thicknesses, and positions of each layer, region, and / or structure may be reduced or enlarged.

[0046] When a corresponding component, such as a layer or area, is referred to as "on another component," it can be directly on that other component, or other components can exist between them. On the other hand, when a component is referred to as "directly on another component (or a variant thereof)," there are no components between them. Furthermore, when a corresponding component is referred to as "on another component," the corresponding component and the other component have an arrangement relationship in the top / vertical direction; the corresponding component can be below or above the other component, and the arrangement relationship in the top / vertical direction is determined by the orientation of the equipment.

[0047] What will be understood is that when a component or layer is said to be "connected" to another component or layer, it can be directly connected to that other component or layer, or there can be intermediate components or layers. Conversely, when a component is said to be "directly connected" to another component or layer, there are no intermediate components or layers.

[0048] The electrical connections or couplings described in this disclosure can refer to direct or indirect connections. In the case of a direct connection, the endpoints of components on two circuits are directly connected or interconnected via conductor segments. In the case of an indirect connection, there are switches, diodes, capacitors, inductors, resistors, other suitable components, or combinations of the aforementioned components between the endpoints of components on two circuits, but the intermediate components are not limited to these.

[0049] The terms "first," "second," "third," "fourth," "fifth," and "sixth" are used to describe components, not to indicate priority or hierarchical relationships. They are only used to distinguish components with the same name.

[0050] It should be noted that, without departing from the spirit of this disclosure, the technical features in the different embodiments described below can be substituted for, recombined, or mixed to form another embodiment.

[0051] Figure 1 This is a schematic diagram of a sensor pixel array having scan lines in rows and sensing lines in columns, according to an embodiment of this disclosure. Figure 1 As shown, Figure 1The sensor pixel array includes nine capacitive sensors, such as capacitive sensor (m-1,n-1), capacitive sensor (m-1,n), capacitive sensor (m-1,n+1), capacitive sensor (m,n-1), capacitive sensor (m,n), capacitive sensor (m,n+1), capacitive sensor (m+1,n-1), capacitive sensor (m+1,n), and capacitive sensor (m+1,n+1), but this disclosure is not limited thereto. The capacitive sensors can be fingerprint sensors for sensing fingerprints, but are not limited thereto. The following uses a fingerprint sensor as an example.

[0052] Each of the nine capacitive sensors is electrically connected to a sensing line and a scan line, respectively. For example, capacitive sensor (m-1, n-1) is electrically connected to a sensing line SSL (m-1) and a scan line SL (n-1). Capacitive sensor (m-1, n) is electrically connected to a sensing line SSL (m-1) and a scan line SL (n). Capacitive sensor (m-1, n+1) is electrically connected to a sensing line SSL (m-1) and a scan line SL (n+1). Capacitive sensor (m, n-1) is electrically connected to a sensing line SSL (m) and a scan line SL (n-1). Capacitive sensor (m, n) is electrically connected to a sensing line SSL (m) and a scan line SL (n). Capacitive sensor (m, n+1) is electrically connected to a sensing line SSL (m) and a scan line SL (n+1). Capacitive sensor (m+1, n-1) is electrically connected to a sensing line SSL (m+1) and a scan line SL (n-1). The capacitive sensor (m+1, n) is electrically connected to the sensing line SSL (m+1) and the scan line SL (n).

[0053] For example, when a user's finger touches the sensor pixel array, and a portion of the user's finger is placed above the capacitive sensor (m,n) during the sensing cycle, the voltage on the scan line SL(n) may be pulled up during the sensing cycle. The capacitance change between the fingerprint ridge and the capacitive sensor (m,n), or the capacitance change between the fingerprint valley and the capacitive sensor (m,n), can be converted into a voltage change by the capacitive sensor (m,n).

[0054] In this disclosure, Figure 1The sensor pixel array described herein is used in electronic devices. The electronic device can be any suitable type of device, such as a touch display device, antenna device, splicing device, sensing device, flexible device, etc., but this disclosure is not limited thereto. The electronic device described herein is a touch display device with touch and display functions. This display device may include liquid crystal (LC), light-emitting diode (LED), quantum dot (QD), phosphor, phosphor, other suitable materials, or combinations of the above materials, but this disclosure is not limited thereto. Light-emitting diodes may include organic light-emitting diodes (OLED), inorganic light-emitting diodes, micro light-emitting diodes, sub-millimeter light-emitting diodes, quantum dot light-emitting diodes (QLED, QDLED), other suitable materials, or combinations of the above materials, but are not limited thereto. Furthermore, the display device in the electronic device can be a color display device or a monochrome display device, and the shape of the electronic device can be rectangular, circular, polygonal, with curved edges, or other suitable shapes. Moreover, the electronic device described below uses touch sensing via an embedded touch device as an example, but the touch sensing method is not limited to this; other suitable touch sensing methods can also be used, as long as they meet all requirements.

[0055] Figure 2 Embodiments of this disclosure Figure 1 The image shows a top view of a capacitive sensor within a sensor pixel array. Taking a capacitive sensor (m,n) as an example, the capacitive sensor (m,n) includes an electrode 200 and an electrode 202. Electrode 202 is disposed on electrode 200. Electrode 200 includes an opening 210 located at the center of electrode 200, but is not limited thereto. Figure 2 As shown, viewed from above, electrode 202 covers the opening 210 of electrode 200. In other words, the size of electrode 202 is larger than the size of the opening 210 of electrode 200.

[0056] In some embodiments, electrode 202 is electrically connected to sensing line SSL(m) and scan line SL(n) via at least one switch, the switch being, for example, a transistor (e.g., a thin-film transistor TFT), located at... Figure 2 Within the dashed circle marked in the middle. In some embodiments, at least one switch is located in a circuit layer (not shown) disposed below electrode 200. This disclosure uses a "transistor" as an example to illustrate the driving switch.

[0057] Figure 3A Embodiments of this disclosure Figure 2 A schematic diagram of a capacitive sensor that interacts with fingerprints. (See diagram below.) Figure 3AAs shown, the capacitive sensor (m,n) further includes a conductive layer 300 disposed below the electrode 200. In other words, the electrode 200 is disposed between the electrode 202 and the conductive layer 300. In some embodiments, the electrode 200 and electrode 202 may be transparent, for example, comprising indium tin oxide (ITO), indium zinc oxide (IZO), other suitable materials, or combinations thereof, but this disclosure is not limited thereto. Depending on the application of the capacitive sensor (m,n), the conductive layer 300 may comprise metal, ITO, other suitable materials, or combinations thereof, but this disclosure is not limited thereto. For example, if the capacitive sensor (m,n) is applied to a display with backlighting, the conductive layer 300 may be transparent. If the capacitive sensor (m,n) is applied to a fingerprint sensing keyboard, the conductive layer 300 may comprise metal or other materials. In some embodiments, a voltage Vr is provided on the conductive layer 300, the voltage Vr being a direct current (DC) voltage, such as ground voltage.

[0058] The capacitive sensor (m,n) further includes an insulating layer 310, an insulating layer 312, and an insulating layer 314. For example... Figure 3A As shown, insulating layer 310 can be disposed between electrode 200 and conductive layer 300. More specifically, insulating layer 310 can be disposed between the aforementioned circuit layer and electrode 200, or insulating layer 310 can be one of the aforementioned circuit layers. Insulating layer 312 can be disposed between electrode 200 and electrode 202. Insulating layer 314 can be disposed between electrode 202 and fingerprint 302. The materials of insulating layers 310, 312, and 314 may include, for example, silicon oxide (SiO2). x ), silicon nitride (SiN) y ), silicon oxynitride (SiO) x N y The insulating materials may include, but are not limited to, polymethyl methacrylate (PMMA), other suitable insulating materials, or combinations thereof. In some embodiments, the materials of insulating layers 310, 312, and 314 may be the same or different, but this disclosure is not limited thereto. In some embodiments, the thickness of insulating layers 310, 312, and 314 may be, for example, 2500 angstroms, but this disclosure is not limited thereto. In some embodiments, the thicknesses of insulating layers 310, 312, and 314 may be different from each other. For example, insulating layer 310 may be thicker than insulating layer 312, and insulating layer 312 may be thicker than insulating layer 314. In some embodiments, insulating layer 314 may be thicker than insulating layer 312, and insulating layer 312 may be thicker than insulating layer 310. In some embodiments, insulating layer 312 may be thicker than insulating layer 310, and insulating layer 312 may be thicker than insulating layer 314, but this disclosure is not limited thereto.

[0059] In some embodiments, the capacitive sensor (m,n) includes a common electrode 304. The common electrode 304 may surround the electrode 202, and a voltage Vr may be provided on the common electrode 304 to shield against electric fields generated by nearby components, for example, by shielding... Figure 1 The electric field generated by the capacitive sensor (m,n-1), capacitive sensor (m-1,n), capacitive sensor (m,n+1), or capacitive sensor (m+1,n) is used to reduce interference from nearby capacitive sensors.

[0060] like Figure 3A As shown, a capacitor Cts is formed between the conductive layer 300 and the electrode 200. A capacitor Crs is formed between the conductive layer 300 and the electrode 202. A capacitor Ctr is formed between the electrodes 200 and 202. A capacitor Cf is formed between the electrode 202 and the fingerprint 302.

[0061] Figure 3B Embodiments of this disclosure Figure 3A The equivalent circuit diagram of a capacitive sensor in [the image / database]. Figure 3B As shown, a sensing signal Vtx, which can be a frequency signal, is provided on electrode 200. Capacitor Cts is disposed between voltage Vr (i.e., conductive layer 300) and electrode 200. Capacitor Crs is disposed between voltage Vr and electrode 202. Capacitor Ctr is disposed between electrode 200 and electrode 202. Capacitor Cf is disposed between electrode 202 and fingerprint 302. In some embodiments, since the sensing signal Vtx is emitted from electrode 200, electrode 200 can be regarded as the transmitter (Tx) of a capacitive sensor (m,n). Since an output voltage Vrx(m,n) can be received from electrode 202, electrode 202 can be regarded as the receiver (Rx) of a capacitive sensor (m,n).

[0062] In some embodiments, capacitor Cts can be 7.76 nanofarads (fF), capacitor Crs can be 13.47 nanofarads, and capacitor Ctr can be 150.52 nanofarads, but are not limited thereto. The capacitance Cf between electrode 202 and the ridge of fingerprint 302 can be 430.30 nanofarads. However, the capacitance Cf between electrode 202 and the valley of fingerprint 302 can be 0.18 nanofarads. Since the output voltage Vrx(m,n) is inversely proportional to the capacitance between electrode 202 and fingerprint 302, the output voltage Vrx(m,n) corresponding to the ridge of fingerprint 302 is less than the output voltage Vrx(m,n) corresponding to the valley.

[0063] For example, when a sensing signal Vtx with an amplitude of 15V is applied to electrode 200, the output voltage Vrx(m,n) corresponding to the ridge of fingerprint 302 with a depth of 0 micrometers (assuming that the ridge of fingerprint 302 is in direct contact with insulating layer 314) can be 3.8V, and the output voltage Vrx(m,n) corresponding to the valley of fingerprint 302 with a depth of 100 micrometers (assuming that the depth of the valley of fingerprint 302 is 100 micrometers) can be 13.75V.

[0064] like Figure 3B As shown, the capacitive sensor (m,n) may further include a control circuit 320. The sensing line SSL (m) can be electrically connected to the electrode 202 through the control circuit 320. In some embodiments, the control circuit 320 may include a transistor 322, a transistor 324, and a transistor 326, but this disclosure is not limited thereto. Transistor 322 may have a first terminal for receiving voltage Vr, a second terminal electrically connected to the electrode 202, and a gate terminal for receiving a reset signal Reset. Transistor 324 may have a first terminal for receiving a sensing signal Vtx, a second terminal electrically connected to the first terminal of transistor 326, and a gate terminal electrically connected to the electrode 202. Transistor 326 has a second terminal electrically connected to the sensing line SSL (m) and a gate terminal electrically connected to the scan line SL (n).

[0065] The reset signal Reset defines the non-sensing period, and the sensing signal Vtx defines the sensing period. In other words, during the non-sensing period, the reset signal Reset can be pulled high and the sensing signal Vtx can be pulled low. During the sensing period, the reset signal Reset can be pulled low and the sensing signal Vtx can be pulled high. During the sensing period, for example, when the sensing signal Vtx is pulled high, the voltage on the scan line SL(n) is also pulled high, transistor 322 can be turned off and transistor 326 can be turned on. The magnitude of the current flowing through transistors 324 and 326 can be determined based on the output voltage Vrx(m,n). In other words, the higher the output voltage Vrx(m,n), the greater the current reaching the sensing line SSL(m) through transistors 324 and 326. Therefore, based on the current flowing through transistors 324 and 326 during the sensing period, the voltage corresponding to the ridge of the fingerprint 302 will exist on the sensing line SSL(m). Similarly, based on the current flowing through transistors 324 and 326 during the sensing cycle, the voltage corresponding to the valley of fingerprint 302 will also exist on the sensing line SSL(m). In some embodiments, the reset signal Reset defines the reset cycle. During the reset cycle, the reset signal Reset is pulled high, the sensing signal Vtx is pulled low, and then the output voltage Vrx(m,n) is initialized to voltage Vr by transistor 322.

[0066] In some embodiments, a voltage readout circuit 330 receives voltages corresponding to the ridges and / or valleys of the fingerprint 302 from the sensing line SSL(m) and converts the voltages into digital signals. For example, the voltage readout circuit 330 may include a transistor 332 and an analog-to-digital converter (ADC) 334. The transistor 332 has a first terminal electrically connected to the sensing line SSL(m) and a second terminal capable of receiving a voltage Vr. The gate terminal of the transistor 332 receives a reset signal Reset, and the input terminal of the ADC 334 is electrically connected to the sensing line SSL(m). During a sensing cycle, when the reset signal Reset is pulled low, the transistor 322 is turned off, and the voltages from the sensing line SSL(m) corresponding to the ridges and / or valleys of the fingerprint 302 are converted into digital signals by the ADC 334. In some embodiments, during a reset cycle, the reset signal Reset is pulled high, the transistor 332 is turned on, and the sensing line SSL(m) is then initialized by the transistor 332 with a voltage Vr.

[0067] In some embodiments, the capacitive sensor (m,n) further includes a current readout circuit (not shown) in place of the voltage readout circuit 330. The current readout circuit may include, for example, a transistor, an operational amplifier, an analog-to-digital converter, and a capacitor. A first input terminal of the operational amplifier is electrically connected to the sensing line SSL(m), a second input terminal of the operational amplifier receives a voltage Vr, and an output terminal of the operational amplifier is electrically connected to the input terminal of the analog-to-digital converter. A capacitor is electrically connected between the sensing line SSL(m) and the output terminal of the operational amplifier. A transistor is electrically connected between the sensing line SSL(m) and the output terminal of the operational amplifier. During a sensing cycle, when the transistor is off, the current from the sensing line SSL(m) corresponding to the ridges and / or valleys of the fingerprint 302 is converted into a voltage by the capacitor and the operational amplifier. The voltage is then converted into a digital signal by the analog-to-digital converter. In some embodiments, the voltage readout circuit 330 and the current readout circuit may be located outside the capacitive sensor (m,n), for example, in other functional chips. In some embodiments, during the reset cycle, the transistor is turned on, the capacitor is initialized, and then the output of the operational amplifier has a voltage Vr as its initial value.

[0068] In some embodiments, when a current readout circuit is used instead of a voltage readout circuit 330, a P-type transistor can be used in the control circuit 320 for transistor 324. When a voltage readout circuit 330 is used, an N-type transistor can be used in the control circuit 320 for transistor 324.

[0069] Figure 4A This is a schematic diagram of a capacitive sensor interacting with a fingerprint, according to an embodiment of this disclosure. Figure 4AAs shown, the capacitive sensor (m,n) includes a conductive layer 400, an electrode 402, an electrode 404, and an electrode 406. Electrode 406 is disposed on top of electrode 402. Electrode 404 covers the opening of electrode 402. In other words, the size of electrode 404 is larger than the size of the opening of electrode 402. Electrode 406 is disposed within the opening of electrode 402. In some embodiments, electrode 406 is substantially coplanar with electrode 402, but this disclosure is not limited thereto.

[0070] A conductive layer 400 is disposed below electrodes 402 and 406. In other words, electrodes 402 and 406 are disposed between the conductive layer 400 and electrode 404. Electrode 404 is disposed between electrode 402 and a fingerprint 420. In some embodiments, a voltage Vr is provided on the conductive layer 400, which may be a direct current (DC) voltage, such as a ground voltage. In some embodiments, electrodes 402, 404, and 406 may be transparent, for example, comprising indium tin oxide (ITO), indium zinc oxide (IZO), other suitable materials, or combinations thereof, but this disclosure is not limited thereto. Based on the application of capacitive sensors (m,n), the conductive layer 400 may comprise metal, ITO, other suitable materials, or combinations thereof, but this disclosure is not limited thereto.

[0071] Figure 4A The capacitive sensor (m,n) further includes insulating layers 430, 432, and 434. The materials of insulating layers 430, 432, and 434 can be the same as those of insulating layers 310, 312, and 314, and will not be described further here. In some embodiments, the thicknesses of insulating layers 430, 432, and 434 can be the same as those of insulating layers 310, 312, and 314, and will not be described further here.

[0072] In some embodiments, Figure 4A The capacitive sensor (m,n) further includes a common electrode 408 and / or a common electrode 410. The common electrode 408 may surround electrode 404, and the common electrode 410 may surround electrode 406. A voltage Vr may also be provided on the common electrode 408 for shielding to reduce interference from nearby capacitive sensors, for example... Figure 1 The sensors can be capacitive sensors (m,n-1), (m-1,n), (m,n+1), or (m+1,n). Alternatively, a voltage Vr can be provided on the common electrode 410 for shielding to reduce interference between electrodes 402 and 406.

[0073] like Figure 4AAs shown, a capacitor Cts' is formed between the conductive layer 400 and the electrode 402. A capacitor Crs' is formed between the conductive layer 400 and the electrode 406. A capacitor Cfs' is formed between the conductive layer 400 and the electrode 404. A capacitor Cfs' is formed between the electrode 402 and the electrode 404. A capacitor Cfr' is formed between the electrode 406 and the electrode 404. A capacitor Cf' is formed between the electrode 404 and the fingerprint 420.

[0074] Figure 4B Embodiments of this disclosure Figure 4A The equivalent circuit diagram of a capacitive sensor in [the image / database]. Figure 4B As shown, a sensing signal Vtx, which can be a frequency signal, is provided on electrode 402. Capacitor Cts' is disposed between voltage Vr (i.e., conductive layer 400) and electrode 402. Capacitor Ctf' is disposed between electrode 402 and electrode 404. Capacitor Cfr' is disposed between electrode 404 and electrode 406. Capacitor Cfs' is disposed between voltage Vr and electrode 404. Capacitor Crs' is disposed between voltage Vr and electrode 406. Capacitor Cf' is disposed between electrode 404 and fingerprint 420.

[0075] In some embodiments, since the sensing signal Vtx is emitted from electrode 402, electrode 402 can be considered as... Figure 4A The transmitter (Tx) of the capacitive sensor (m,n). Because an output voltage Vrx(m,n) can be received from electrode 406, electrode 406 can be considered as... Figure 4A The receiver (Rx) of the capacitive sensor (m,n).

[0076] In some embodiments, capacitor Cts' may be 7.76 NpF, capacitor Ctf' may be 150.52 NpF, and capacitor Cfr' may be 141.66 NpF. Capacitor Crs' may be 3.45 NpF. Capacitor Cfs' may be 10.01 NpF, but is not limited thereto. The capacitance Cf' between electrode 404 and the ridge of fingerprint 420 may be 430.30 NpF. However, the capacitance Cf' between electrode 404 and the valley of fingerprint 420 may be 0.18 NpF. Since the output voltage is inversely proportional to the capacitance between electrode 404 and fingerprint 420, the output voltage Vrx(m,n) corresponding to the ridge of fingerprint 420 is less than the output voltage Vrx(m,n) corresponding to the valley.

[0077] For example, when a sensing signal Vtx with an amplitude of 15V is applied to electrode 402, the output voltage Vrx(m,n) corresponding to the ridge of fingerprint 420 with a depth of 0 micrometers (assuming that the ridge of fingerprint 420 is in direct contact with insulating layer 434) can be 3.71V, and the output voltage Vrx(m,n) corresponding to the valley of fingerprint 420 with a depth of 100 micrometers (assuming that the depth of the valley of fingerprint 420 is 100 micrometers) can be 13.43V.

[0078] like Figure 4B As shown, the capacitive sensor (m,n) may further include a control circuit 440. The sensing line SSL (m) can be electrically connected to the electrode 406 through the control circuit 440. In some embodiments, the control circuit 440 may include a transistor 442, a transistor 444, and a transistor 446. Transistor 442 may have a first terminal for receiving voltage Vr, a second terminal electrically connected to the electrode 406, and a gate terminal for receiving a reset signal Reset. Transistor 444 may have a first terminal for receiving a sensing signal Vtx, a second terminal electrically connected to the first terminal of transistor 446, and a gate terminal electrically connected to the electrode 406. Transistor 446 has a second terminal electrically connected to the sensing line SSL (m) and a gate terminal electrically connected to the scan line SL (n).

[0079] Similarly, during the sensing cycle, the reset signal Reset is pulled low, and the sensing signal Vtx is pulled high. During the sensing cycle, for example, when the sensing signal Vtx is pulled high, the voltage on the scan line SL(n) is also pulled high. Transistor 442 can be turned off, and transistor 446 can be turned on. The magnitude of the current flowing through transistors 444 and 446 can be determined based on the output voltage Vrx(m,n). In other words, the higher the output voltage Vrx(m,n), the greater the current reaching the sensing line SSL(m) through transistors 444 and 446. Therefore, based on the current flowing through transistors 444 and 446 during the sensing cycle, the voltage corresponding to the ridge of the fingerprint 420 will exist on the sensing line SSL(m). Similarly, based on the current flowing through transistors 444 and 446 during the sensing cycle, the voltage corresponding to the valley of the fingerprint 420 will also exist on the sensing line SSL(m). In some embodiments, before the sensing cycle, during the reset cycle, the reset signal Reset is pulled high and the sensing signal Vtx is pulled low, and then the output voltage Vrx(m,n) is initialized to voltage Vr by transistor 422.

[0080] In some embodiments, a voltage readout circuit 450 receives voltages corresponding to the ridges and / or valleys of the fingerprint 420 from the sensing line SSL(m) and converts the voltages into digital signals. For example, the voltage readout circuit 450 may include a transistor 452 and an analog-to-digital converter (ADC) 454. The transistor 452 has a first terminal electrically connected to the sensing line SSL(m) and a second terminal capable of receiving a voltage Vr. The gate of the transistor 452 receives a reset signal Reset, and the input of the ADC 454 is electrically connected to the sensing line SSL(m). During a sensing cycle, when the reset signal Reset is pulled low, the transistor 452 is turned off, and the voltages from the sensing line SSL(m) corresponding to the ridges and / or valleys of the fingerprint 420 are converted into digital signals by the ADC 454. In some embodiments, during a reset cycle preceding the sensing cycle, the reset signal Reset is pulled high, the transistor 452 is turned on, and the sensing line SSL(m) is then initialized by the transistor 452 with a voltage Vr.

[0081] In some embodiments, Figure 4A The capacitive sensor (m,n) further includes a current readout circuit (not shown) to replace the voltage readout circuit 450. The current readout circuit may include, for example, a transistor, an operational amplifier, an analog-to-digital converter, and a capacitor. A first input of the operational amplifier is electrically connected to the sensing line SSL(m), a second input of the operational amplifier receives a voltage Vr, and the output of the operational amplifier is electrically connected to the input of the analog-to-digital converter. A capacitor is electrically connected between the sensing line SSL(m) and the output of the operational amplifier. A transistor is electrically connected between the sensing line SSL(m) and the output of the operational amplifier. During the sensing cycle, when the transistor is off, the current from the sensing line SSL(m) corresponding to the ridges and / or valleys of the fingerprint 420 is converted into a voltage by the capacitor and the operational amplifier. The voltage is then converted into a digital signal by the analog-to-digital converter. In some embodiments, the voltage readout circuit 450 and the current readout circuit may be located outside the capacitive sensor (m,n), for example, in other functional chips. In some embodiments, during a reset period prior to the sensing period, the transistor is turned on, the capacitor is initialized, and then the output of the operational amplifier has a voltage Vr as its initial value.

[0082] In some embodiments, when a current readout circuit is used instead of a voltage readout circuit 450, a P-type transistor can be used in the control circuit 440. When a voltage readout circuit 450 is used, an N-type transistor can be used in the control circuit 440.

[0083] In some embodiments, Figure 3B The control circuit 320 and Figure 4BEach of the control circuits 440 may include a transistor (not shown). The gate of the transistor is electrically connected to scan line SL(n), a first terminal of the transistor is electrically connected to electrode 202 or electrode 406, and a second terminal of the transistor is electrically connected to sensing line SSL(m). In some embodiments, having Figure 3B The control circuit 320 or having Figure 4B The capacitive sensor (m,n) in the control circuit 440 can be referred to as an active pixel. A capacitive sensor (m,n) with a control circuit containing a transistor can be referred to as a passive pixel.

[0084] Figure 1 , Figure 2 , Figure 3A , Figure 3B , Figure 4A ,and Figure 4B The capacitive sensor in the medium provides stray capacitance sensing. Stray capacitance sensing achieves the same large capacitance change as self-capacitance sensing and the same simple readout circuit as mutual capacitance sensing. The simple sensor structure with simple readout circuitry achieves large, flexible, and / or fast scan frames per second (FPS) by utilizing in-plane switching liquid crystal (IPS-LC) array technology and / or thinner systems without additional devices such as light sources for optical FPS.

[0085] The embodiments of this disclosure have been disclosed above, but are not intended to limit the scope of this disclosure. Those skilled in the art can make modifications and refinements without departing from the spirit and scope of the embodiments of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the appended claims.

Claims

1. A capacitive sensor, characterized by The application relates to a fingerprint sensor, comprising: a first electrode comprising at least one opening; at least one second electrode disposed on the first electrode; and a first common electrode surrounding the at least one second electrode, wherein the at least one second electrode covers the at least one opening of the first electrode. Further comprising a conductive layer disposed below the first electrode.

2. The capacitive sensor of claim 1, wherein, Further comprising a sensing line electrically connected to the at least one second electrode.

3. The capacitive sensor of claim 1, wherein, Further comprising a control circuit; wherein the sensing line is electrically connected to the at least one second electrode through the control circuit.

4. The capacitive sensor of claim 3, wherein, A voltage is provided on the first common electrode, and a conductive layer is disposed below the first electrode.

5. The capacitive sensor of claim 1, wherein, Further comprising a first insulating layer disposed between the conductive layer and the first electrode, a second insulating layer disposed between the first electrode and the at least one second electrode, and a third insulating layer disposed on the at least one second electrode.

6. The capacitive sensor of claim 2, wherein, A first capacitor is formed between the conductive layer and the first electrode, a second capacitor is formed between the conductive layer and the at least one second electrode, a third capacitor is formed between the first electrode and the at least one second electrode, and a fourth capacitor is formed between the at least one second electrode and a fingerprint.

7. The capacitive sensor of claim 2, wherein, A sensing signal is provided on the first electrode.

8. The capacitive sensor of claim 5, wherein, A control circuit comprises a first transistor, a second transistor, and a third transistor; the first transistor has a first end receiving the voltage, a second end electrically connected to the at least one second electrode, and a gate end receiving a reset signal; the second transistor has a first end receiving the sensing signal, a second end electrically connected to a first end of the third transistor, and a gate end electrically connected to the at least one second electrode; and the third transistor has a second end electrically connected to a sensing line, and a gate end electrically connected to a scanning line.

9. The capacitive sensor of claim 8, wherein, Further comprising a voltage readout circuit; the voltage readout circuit comprises a first transistor and an analog-to-digital converter; the first transistor has a first end electrically connected to a sensing line, a second end receiving the voltage, and a gate end receiving a reset signal; and an input of the analog-to-digital converter is electrically connected to the sensing line.

10. The capacitive sensor of claim 5, wherein, Further comprising at least one third electrode disposed in the opening of the first electrode.

11. The capacitive sensor of claim 1, wherein, Further comprising a conductive layer disposed below the first electrode and the at least one third electrode; the conductive layer provides a voltage.

12. The capacitive sensor of claim 11, wherein, Further comprising a second common electrode; the second common electrode is disposed between the first electrode and the at least one third electrode, and a voltage is provided on the second common electrode.

13. The capacitive sensor of claim 11, wherein, A first capacitor is formed between the conductive layer and the first electrode, a second capacitor is formed between the conductive layer and the at least one second electrode, a third capacitor is formed between the conductive layer and the at least one third electrode, a fourth capacitor is formed between the first electrode and the at least one second electrode, a fifth capacitor is formed between the at least one second electrode and the at least one third electrode, and a sixth capacitor is formed between the at least one second electrode and a fingerprint.

14. The capacitive sensor of claim 12, wherein, Further comprising a sensing line electrically connected to the at least one third electrode.

15. The capacitive sensor of claim 12, wherein, ​ 16. The capacitive sensor of claim 15, wherein, Further comprising a control circuit; the sensing line is electrically connected to the at least one third electrode through the control circuit.

17. The capacitive sensor of claim 16, wherein, A sensing signal is provided on the first electrode.

18. The capacitive sensor of claim 17, wherein, The control circuit comprises a first transistor, a second transistor, and a third transistor; the first transistor has a first end receiving the voltage, a second end electrically connected to the at least one third electrode, and a gate end receiving a reset signal; the second transistor has a first end receiving the sensing signal, a second end electrically connected to a first end of the third transistor, and a gate end electrically connected to the at least one third electrode; the third transistor has a second end electrically connected to the sensing line, and a gate end electrically connected to a scan line.

19. The capacitive sensor of claim 15, wherein, Further comprising a voltage readout circuit; the voltage readout circuit comprises a first transistor and an analog-to-digital converter; the first transistor has a first end electrically connected to the sensing line, a second end receiving the voltage, and a gate end receiving a reset signal; and an input of the analog-to-digital converter is electrically connected to the sensing line.

Images