Multi-functional capacitive sensing chip

Abstract

This invention relates to a multi-functional capacitive sensing integrated circuit, comprising: a substrate, a signal processing circuit layer, an interconnect layer, an electrode array layer and a dielectric layer. The signal processing circuit layer is disposed on the substrate, and an algorithm is used to extract fingerprint features and handwriting features. The interconnect layer is electrically coupled to the signal processing circuit layer for transmitting capacitive signals. The electrode array layer is arranged in a matrix array to detect changes in capacitance caused by contact pressure and movement trajectories of a contact object. The signal processing layer generates digital information of fingerprint patterns and handwriting trajectories. The dielectric layer is electrically coupled to the signal processing circuit layer and is used to isolate electrodes, prevent short circuits, and enhance capacitive effects. It is formed of a high dielectric constant dielectric material, a pressure-sensitive material, or an insulating material.

Description

Technical Field

[0001] This invention relates to a composite functional capacitive sensing chip, and more specifically to an innovative composite functional capacitive sensing chip that integrates fingerprint recognition and stylus sensing functions, thereby realizing the integration of multiple biometric identification and handwriting input. Prior Technology

[0002] Capacitive fingerprint sensors are one of the most common biometric technologies used in smartphones, tablets, and other mobile devices. They work by measuring the capacitance difference between the finger and the sensor surface to identify unique fingerprint patterns, thus enabling fast and secure authentication. Today, capacitive fingerprint sensors are widely used in various electronic products, from high-end flagship models to budget phones.

[0003] After years of technological development, capacitive fingerprint sensors have become very mature, possessing the characteristics of fast recognition and high accuracy. As a biometric feature, fingerprints are highly unique and difficult to replicate, providing users with reliable security. Currently, capacitive fingerprint sensors are mainly divided into the following types: traditional press-type, a common early design that requires users to press the sensor for recognition, but occupies space on the front panel; side-button type, integrating the sensor into the power button or volume button on the side of the phone, combining power button functionality with fingerprint recognition; and under-screen optical type, hiding the sensor under the screen, using optical technology to penetrate the screen for fingerprint recognition, further enhancing the screen's integrity.

[0004] Furthermore, early capacitive styluses could only simulate the touch functions of fingers. However, with the rapid advancement of technology, many electronic products began to adopt touch panels as their operating interface. In addition to allowing users to input via gestures or fingers, they also allowed users to perform operations such as pointing, writing, or drawing by holding a stylus. Today, styluses have been further enhanced in functionality, enabling pressure sensing and tilt angle recognition, allowing users to enjoy a more refined user experience when drawing and taking notes.

[0005] However, there are currently no touch panels on the market that simultaneously feature fingerprint recognition and support stylus writing. Existing solutions typically optimize only one function, such as integrating fingerprint recognition into the touch panel or improving the sensitivity and functionality of the stylus, but they cannot simultaneously meet the needs of both.

[0006] This technological limitation primarily stems from the technical challenges of integrating multiple functions. The touch panel needs to accurately sense the pressure, tilt angle, and rapid writing trajectory of the stylus, while simultaneously possessing highly sensitive and accurate fingerprint recognition capabilities. These two aspects can potentially interfere with each other in hardware design and signal processing. For example, the capacitive signal of the fingerprint sensor is easily affected by signals generated during stylus operation, leading to a decrease in recognition accuracy. Furthermore, the materials and manufacturing technology of the touch panel must simultaneously support the requirements of both stylus and fingerprint recognition, further increasing the complexity of technological development.

[0007] In summary, in order to overcome the aforementioned shortcomings, the inventors of this case have devoted considerable research and development energy and spirit to continuous breakthroughs and innovations in this field, hoping to solve the deficiencies of conventional methods with novel technical means, thereby bringing better products to society and promoting industrial development. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides an electronic signature chip with capacitive sensing capabilities, which simultaneously supports fingerprint recognition and stylus writing. This invention can accurately sense stylus pressure, tilt angle, and rapid writing trajectory, and achieves high sensitivity and accuracy in fingerprint recognition to meet the needs of multi-functional use.

[0009] To achieve the aforementioned objectives, this invention discloses a composite functional capacitive sensing chip, which is a capacitive sensing and recognition device possessing at least multiple functions including fingerprint recognition, electronic signature, and handwriting trajectory (handwriting) recognition. The composite functional capacitive sensing chip includes: a substrate, a signal processing circuit layer, an interconnect layer, an electrode array layer, and a dielectric layer. First, the substrate is constructed from materials such as glass, quartz, silicon oxide, ceramic, or polymer. Second, the signal processing circuit layer is disposed above the substrate to extract fingerprint features and / or handwriting features.

[0010] Furthermore, the interconnect layer is electrically coupled to the signal processing circuit layer and used to transmit a capacitive signal. The interconnect layer is made of at least one metallic material selected from copper, aluminum, gold, silver, alloys, and combinations thereof.

[0011] Furthermore, the electrode array layer is electrically coupled to the interconnect layer and includes a plurality of electrodes arranged in a plurality of matrix arrays. Each of the plurality of electrodes is made of at least one metal or metal-containing material selected from copper, aluminum, gold, silver, alloys, and combinations thereof, and is used to sense a capacitance value change function caused by a temporal action of a contact object relative to the electrode array layer, thereby obtaining fingerprints, writing traces (handwriting or text), and / or electronic signatures. In addition, the contact object is at least one selected from the following: a finger, palm, toe, electronic pen, writing instrument, and combinations thereof of an individual biological entity; the timing action includes: the contact object approaching or touching the electrode array layer; the contact object being stationary, remaining, or held on the electrode array layer; or performing a movement, motion, or travel action by contacting the electrode array layer; each electrode array further includes at least one varactor capacitor, the capacitance value of which varies from 1fF to 10fF; the signal processing circuit layer is able to generate digital information representing a fingerprint pattern and a stroke trajectory based on parameters such as capacitance value, writing speed, and writing pressure, combined with a specific algorithm.

[0012] In the composite functional capacitive sensing chip of the present invention, the signal processing circuit layer processes a fingerprint image of the finger fingerprint, and converts a first capacitance value C1(x,y) collected by the electrode array layer into a corresponding primitive value I(x,y) through a gray-scale mapping function f. The gray-scale mapping function f adopts a linear function form and satisfies the following relationship function (1): I(x,y)=f(C1(x,y)) ----------(1); Where C1(x,y) represents the first capacitance value measured by the electrode array layer at position (x,y); I(x,y) refers to the gray value of the primitive at position (x, y), representing the brightness of the image at (x, y).

[0013] In the composite functional capacitive sensing chip of the present invention, the signal processing circuit layer processes a stroke image of the pen tip of the writing instrument. Based on a second capacitance value C2(x,y), a writing speed v(x,y,t), and a writing pressure p(x,y,t) collected by the electrode array layer, the stroke trajectory is reconstructed through a function g that combines speed, pressure, and capacitance changes. The function g adopts a Kalman filtering model and satisfies the following relationship function (2): P(x,y,t)=g(C2(x,y,t),v(x,y,t),p(x,y,t)) ---------- (2); Where C2(x,y,t) represents the second capacitance value of the electrode array layer measured at time t and position (x, y); v(x, y, t) represents the writing speed of the pen tip at time t and position (x, y); and p(x, y, t) represents the writing pressure applied by the pen tip at time t and position (x, y).

[0014] In the composite functional capacitive sensing chip of the present invention, the feature extraction of the fingerprint pattern includes extracting the ridge bifurcation point and termination point in the fingerprint image. The fingerprint image is generated as a grayscale image based on the change of a first capacitance value. The area with a larger first capacitance value corresponds to the ridge of the fingerprint, and the area with a smaller capacitance value corresponds to the valley of the fingerprint.

[0015] In the composite functional capacitive sensing chip of the present invention, the feature extraction of the handwriting trajectory includes analyzing the pressure, speed, direction or turning point of the writing to generate a signature verification handwriting trajectory; the reconstruction of the handwriting trajectory is based on the path map generated by the change of a second capacitance value, and the thickness, pressure and / or speed of the writing are analogized to the change of the second capacitance value.

[0016] Furthermore, the dielectric layer is electrically coupled to the electrode array layer and is used to isolate the electrodes, prevent short circuits, and enhance the capacitance effect. The dielectric layer has a sawtooth microstructure and is formed of a dielectric material with a high dielectric constant, a varistor material, or an insulating material.

[0017] The composite functional capacitive sensing chip of the present invention further includes a protective layer disposed above the electrode array layer, which is made of a wear-resistant material such as sapphire or glass.

[0018] The composite functional capacitive sensing chip of the present invention further includes an electronic device electrically coupled to the signal processing circuit layer, which displays a fingerprint or a writing recognition status information according to the received control signal.

[0019] In the composite functional capacitive sensing chip of the present invention, the electrode array layer adopts at least one of the following: a row-column structure, a curved structure, a microchannel structure, a microsphere array structure, or an irregular arrangement structure, so as to improve the sensing accuracy and the resolution of the fingerprint image.

[0020] In the composite functional capacitive sensing chip of the present invention, the signal processing layer employs at least one of wavelet transform or deep learning algorithm to compare and analyze the extracted fingerprint features.

[0021] In the composite functional capacitive sensing chip of the present invention, the electronic device is a microdisplay built into the composite functional capacitive sensing chip or an externally connected device. Simple Explanation of the Diagram

[0022] Figure 1 is a cross-sectional view of the composite functional capacitive sensing chip of Embodiment 1 of the present invention. Figure 2 is a schematic diagram of the operation of the composite functional capacitive sensing chip of Embodiment 1 of the present invention. Figure 3 is a schematic block diagram of the composite functional capacitive sensing chip and sensor driving integrated circuit of Embodiment 1 of the present invention. Figure 4 is another schematic block diagram of the composite functional capacitive sensing chip of Embodiment 1 of the present invention. Figure 5 shows the signal waveforms of the initial sensing signal Si and control signal Sc of the capacitive fingerprint sensing electronic signature chip in Embodiment 1 of the present invention. Figure 6A is a circuit diagram of the amplifier circuit of the capacitive fingerprint sensing electronic signature chip of Embodiment 1 of the present invention. Figure 6B is a circuit diagram of the amplifier of the capacitive fingerprint sensing electronic signature chip in Embodiment 1 of the present invention. Figure 7 is a cross-sectional view of the composite functional capacitive sensing chip of Embodiment 2 of the present invention. Figure 8 is a schematic block diagram of the composite functional capacitive sensing chip of Embodiment 3 of the present invention. Figure 9 shows a structural diagram of the sensing matrix of the composite functional capacitive sensing chip of Embodiment 3 of the present invention. Implementation

[0023] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the invention are now described in detail with reference to the accompanying drawings. The detailed description and technical content of the present invention are illustrated below in conjunction with the accompanying drawings; however, the accompanying drawings are provided for reference and illustration only and are not intended to limit the scope of the invention.

[0024] In addition, it should be understood that when a component is indicated as "connected" or "electrically coupled" to another component, it can be directly connected or coupled to the other component, or there can be an intermediate component.

[0025] Please refer to Figure 1, which is a cross-sectional view of the composite functional capacitive sensing chip of Embodiment 1 of the present invention; and Figure 2 shows an operation schematic diagram of the composite functional capacitive sensing chip of Embodiment 1 of the present invention.

[0026] As shown in Figures 1 and 2, this invention describes a composite functional capacitive sensing chip 1, which is a capacitive sensing and recognition device with at least multiple functions including fingerprint recognition, electronic signature, and handwriting recognition. The composite functional capacitive sensing chip includes a substrate 10, a signal processing circuit layer 20, an interconnect layer 30, an electrode array layer 40, and a dielectric layer 50. The substrate 10 is made of materials such as glass, quartz, silicon oxide, ceramic, or polymer.

[0027] As shown in Figure 1, the signal processing circuit layer 20 is disposed above the substrate 10 to extract fingerprint features and handwriting features. The signal processing layer 20 employs at least one of wavelet transform or deep learning algorithm to compare and analyze the extracted fingerprint features.

[0028] The interconnect layer 30 is electrically coupled to the signal processing circuit layer 20 and is used to transmit a capacitive signal. The interconnect layer 30 is made of at least one metallic material selected from copper, aluminum, gold, silver, alloys, and combinations thereof.

[0029] The electrode array layer 40 is electrically coupled to the interconnect layer 30 and includes a plurality of electrodes arranged in a plurality of matrix arrays. Each of the plurality of electrodes is made of at least one metal or a metal-containing material selected from copper, aluminum, gold, silver, alloys, and combinations thereof, and is used to sense a capacitance value change function caused by a temporal action of a contact object relative to the electrode array layer, thereby obtaining fingerprints, writing traces (handwriting or text), and / or electronic signatures. The contact object is at least one selected from a biological individual's finger, palm, toe, electronic pen, writing instrument, and combinations thereof. The temporal action includes: the contact object approaching or touching the electrode array layer, the contact object being stationary, remaining, or held on the electrode array layer, or performing a movement, motion, or travel action while in contact with the electrode array layer. Each electrode array further includes at least one varactor capacitor, the capacitance of which varies from 1fF to 10fF; the signal processing circuit layer 20 can generate digital information representing a fingerprint pattern and a stroke trajectory based on parameters such as capacitance value, writing speed and writing pressure, combined with a specific algorithm.

[0030] The dielectric layer 50 is electrically coupled to the electrode array layer 40 and is used to isolate the electrodes, prevent short circuits, and enhance the capacitance effect. The dielectric layer has a sawtooth microstructure and is formed of a dielectric material with a high dielectric constant, a varistor material, or an insulating material.

[0031] Please refer to Figures 3 and 4. Figure 3 is a schematic block diagram of the composite functional capacitive sensing chip and sensor driving integrated circuit of Embodiment 1 of the present invention; and Figure 4 is another schematic block diagram of the composite functional capacitive sensing chip of Embodiment 1 of the present invention.

[0032] As shown in Figures 3 and 4, the composite-functional capacitive sensing chip 1 is electrically connected to a sensor driving integrated circuit via a data line. An internal circuit 12 of the sensor driving integrated circuit includes a clock generator 121, a receiving sensing unit 122, a transmitting sensing unit 123, a signal buffer unit 124, and a signal transmission element 125. The receiving sensing unit 122 includes an amplifier circuit 1221, a filter circuit 1222, an A / D conversion circuit 1223, and a feature extraction circuit 1224. An electronic device 126 is electrically coupled to the internal circuit 12 and displays a fingerprint or handwriting recognition status information based on the received control signal. The electronic device 126 is either a miniature display built into the composite-functional capacitive sensing chip or an externally connected device.

[0033] As shown in Figures 3 and 4, with the help of the clock signal Sck generated by the clock generator 121, the receiving sensing unit 122, the transmitting sensing unit 123, the signal buffer unit 124, and the signal transmission element 125 perform regular sensing steps. During the sensing steps, in response to an activation command provided by the user, the transmitting sensing unit 123 is configured to receive the clock signal Sck and generate an initial sensing signal Si and a control signal Sc, and transmits the initial sensing signal Si to the user's finger through the signal buffer unit 124 and the signal transmission element 125. The transmitting sensing unit 123 is configured to send the initial sensing signal Si or the control signal Sc to the receiving sensing unit 122 to synchronize the received sensing signal and the elements in the receiving sensing unit 122, such as the switch 1220. The initial sensing signal Si may be similar to the control signal Sc in waveform or sampling frequency. In one embodiment, the initial sensing signal Si and the control signal Sc have different waveforms but are still in phase with the control signal; for example, the initial sensing signal Si has a signal transition edge corresponding to the control signal Sc. In another embodiment, the signal edge of the initial sensing signal Si is synchronized with the signal edge of the control signal Sc. In yet another embodiment, the on / off state of the initial sensing signal Si can be the same as or opposite to the on / off state of the control signal Sc.

[0034] Please refer to Figure 5, which shows the signal waveforms of the initial sensing signal Si and control signal Sc of the capacitive fingerprint sensing electronic signature chip in Embodiment 1 of the present invention.

[0035] As shown in Figure 5, the initial sensing signal Si includes a signal amplitude Vin with a sensing period Tm. The sensing period Tm includes a reset period Tr and a sampling period Ts, and the operating period of the control signal Sc is expressed as Dc = Tr / Ts. The clock generator 121 provides an initial sensing signal Si with a non-zero input voltage Vin in the on state and a substantially zero voltage (or contact level) in the off state. The initial sensing signal Si provides a signal conversion voltage +Vin with a rising edge, corresponding to or substantially aligned with the start time of the sampling period Ts. The signal polarity +Vin appearing at the rising edge of the initial sensing signal Si can be used as a sensing voltage, and thus the sensing voltage can be generated during the sampling period Ts. The sensing voltage can have the same signal polarity as the signal conversion voltage, such as a positive or negative voltage.

[0036] Furthermore, the signal processing circuit layer 20 processes a fingerprint image of the finger fingerprint, and converts a first capacitance value C1(x,y) acquired by the electrode array layer 40 into a corresponding primitive value I(x,y) through a grayscale mapping function f. The grayscale mapping function f adopts a logarithmic function form and satisfies the following relationship function (1): I(x,y)=f(C1(x,y)) ----------(1); Where C1(x,y) represents the first capacitance value measured by the electrode array layer at position (x,y); I(x,y) refers to the gray value of the primitive at position (x, y), representing the brightness of the image at (x, y).

[0037] The fingerprint feature extraction includes extracting the ridge bifurcation points and termination points in the fingerprint image. The fingerprint image is generated as a grayscale image based on the change of a first capacitance value. The area with a larger first capacitance value corresponds to the ridge of the fingerprint, and the area with a smaller first capacitance value corresponds to the valley of the fingerprint.

[0038] Each element 41 in the electrode array layer 40 contains a microcapacitor used to detect the ridges (contact portions) and valleys (non-contact portions) of the fingerprint. When a fingerprint touches the electrode array layer 40, the conductivity of the fingerprint ridges changes the charging level of the microcapacitor, while the fingerprint valleys, lacking contact, generate different capacitance values. These capacitance values ​​are converted into electronic signals to generate a complete fingerprint image.

[0039] During the reset cycle Tr, the capacitor within this element 41 is reset to a reference state, ensuring accuracy for each scan. During the sampling cycle Ts, the capacitor is charged based on the differences in fingerprint ridges and valleys, generating a corresponding voltage signal as a sensing result. Vin is used to charge the capacitor; voltage changes reflect the capacitor's charging and discharging behavior, thus indirectly reflecting the physical characteristics of the fingerprint. The control signal Sc controls the opening or closing of the switch, determining the capacitor's behavior at different operating stages. During the reset cycle Tr, the control signal Sc partially closes the switch, allowing the capacitor to release residual charge and return to its initial state (e.g., ground potential). During the sampling cycle Ts, the control signal Sc opens the switch, allowing the capacitor to charge through the input signal Vin, thereby sensing changes in fingerprint capacitance. The synchronous switching of the control signal Sc ensures that each capacitor element completes charging or discharging at the correct time.

[0040] Furthermore, the signal buffer unit 124 is configured to buffer the initial sensing signal Si and generate a buffered sensing signal Sb. The signal buffer unit 124 can also convert the voltage or current level of the initial sensing signal Si to another signal level to provide the driving capability required for the sensing step. The signal buffer unit 124 includes at least one of a current amplifier circuit 1221 and a level shifter, configured to generate the buffered sensing signal Sb in response to the initial sensing signal Si.

[0041] The signal transmission element 125 is configured to generate a transmission sensing signal St in response to the buffer sensing signal Sb and transmit it to the user's finger. The signal transmission element 125 can transmit the buffer sensing signal Sb by contacting the finger or in a non-contact manner. In touch mode, the signal transmission element 125 includes a conductive layer and / or a frame, through which the buffer sensing signal Sb is transmitted as the transmission sensing signal St. During a touch event, the finger approaches or contacts the electrode array layer 40 and receives the transmission sensing signal St. A capacitance Cfinger is thus generated between the finger and the element 41. The element 41 can generate a received sensing signal Sr, which is generated by the transmission sensing signal St transmitted to the finger and the capacitance Cfinger in response to the touch event.

[0042] The receiving sensing control unit 122 is configured to receive the sensing signal Sr and generate a digital sensing signal Sd, which represents the sensing result provided by the graphic element 41 in response to a touch event. The digital sensing signal Sd can be transmitted to an electronic device, where the digital sensing signals Sd detected by different parts of the finger by different graphic elements 41 are processed to form a processing signal Sp representing a fingerprint image of the finger.

[0043] The amplifier circuit 1221 is configured to increase the quantization resolution of the A / D conversion circuit 1223 and reduce noise introduced during the sensing step. The amplifier circuit 1221 includes an operational (OP) amplifier, a voltage amplifier, a current amplifier, a transconductance amplifier, or a transimpedance amplifier. In a preferred embodiment, the amplifier circuit 1221 includes a two-stage amplification design, and the A / D conversion circuit 1223 is configured to convert the analog value of the received sensing signal Sr into a digital signal in digital form for use as the digitized sensing signal Sd, thereby facilitating processing by the electronic device 126. The A / D conversion circuit 1223 includes a successive approximation register (SAR) ADC, a delta-slope (ΔΣ) ADC, a dual-slope ADC, a pipelined ADC, a flash ADC, etc.

[0044] As shown in Figure 4, the amplifier circuit 1221 includes an amplifier 1225, a feedback capacitor 1226, and a switch 1220. The amplifier 1225 is connected in parallel to the feedback capacitor 1226 and the switch 1220. The amplifier 1225 includes an inverting terminal (-) and a non-inverting terminal (+), the non-inverting terminal being connected to a supply voltage Vz. The supply voltage Vz is predetermined to be Vdd / 2. The inverting terminal is coupled to a resistive element Ri. The amplifier 1225 also includes an output terminal to provide an output signal Sa as an amplified sensing signal.

[0045] In the first stage of the sensing step, during the reset period Tr of the sensing period Tm, the switch 1220 is closed, causing the amplifier 1225 to be configured in reset mode and forced to its initial state with unit gain. In the second stage of the sensing step, during the sampling period Ts of the sensing period Tm, the switch 1220 is opened, causing the amplifier 1225 to be configured in amplification mode and to generate the output signal Sa by receiving amplified sensing signal Sr. The timing of the switch 1220 can be synchronized or in phase with the control signal Sc; for example, the open and closed states of the switch 1220 correspond to the off and on states of the control signal Sc, respectively.

[0046] The resistive element Ri is electrically coupled between the electrode array layer 40 and the amplifier 1225 of the amplifier circuit 1221. The resistive element Ri can be a resistor. It is formed by a semiconductor processing process in a metallization layer above the substrate used to form the receiving sensing unit 122 or the transmitting sensing unit 123, and is electrically coupled to the electrode array layer 40 and the amplifier 1225. The resistive element Ri can include a diffused resistor, an ion-implanted resistor, a thin-film resistor, a polysilicon resistor, etc. The resistive element Ri is an independent resistor external to the electrode array layer 40 or the amplifier 1225. The resistance of the resistive element Ri is appropriately determined to enhance the stability of the amplifier 1225. The dielectric properties of the substrate 10 of the electrode array layer 40 may cause the substrate capacitance Cs to be electrically coupled to the amplifier circuit 1221. The substrate capacitance Cs can cause stability problems in the amplifier 1225, thereby severely affecting the operating bandwidth or operating current of the amplifier 1225.

[0047] Please refer to Figures 6A and 6B. Figure 6A is a circuit diagram of the amplifier circuit of the capacitive fingerprint sensing electronic signature chip of the present invention; and Figure 6B is a circuit diagram of the amplifier of the capacitive fingerprint sensing electronic signature chip of the present invention.

[0048] As shown in Figures 6A and 6B, during small-signal analysis in the reset phase, the inverting terminal (-) is disconnected from the feedback loop. Furthermore, since the amplifier 1225 is configured to amplify the input voltage Vt during the reset period Tr, the switch 1220 is closed. The inverting terminal (-) of the amplifier 1225 is directly coupled to the conductive interconnection circuit between the electrode array layer 40 and the receiving sensing unit 122, where the element 41 or bit of the electrode array layer 40 is located. The total resistance between the electrode array layer 40 and the amplifier circuit 1221 is negligible. In small-signal analysis, the feedback loop caused by the amplifier 1225 can be represented as a parasitic capacitor Cp and a substrate capacitor Cs connected in parallel at the output node N2 (also labeled "Vout") of the amplifier 1225.

[0049] As shown in Figure 6B, in terms of the two-stage operational amplifier structure and small-signal analysis, the amplifier 1225 includes a first stage, which is composed of a current source I1 connected in parallel with a resistor R1 and a capacitor C1 at the output node N1 of the first stage S1. The first stage S1 provides an output terminal Vo1 at the output node N1, and the current source I1 is represented as I1 = -gm1∙Vt.

[0050] As shown in Figure 6B, the second stage S2 is coupled to the first stage S1 via a coupling capacitor Cc. In small-signal analysis, the second stage S2 consists of a current source I2 connected in parallel with a resistor R2 and a load capacitor CL. The capacitance of the load capacitor CL can be expressed as the sum of the capacitances of the substrate capacitor Cs and the parasitic capacitor Cp, i.e., CL = Cs + Cp. The current source I2 is represented as I2 = gm2∙Vo1. The second stage S2 provides the output voltage Vout of the amplifier's output signal Sa.

[0051] Please refer to Figure 7, which is a cross-sectional view of the composite functional capacitive sensing chip of Embodiment 2 of the present invention.

[0052] Example 2 is largely the same as Example 1, except that Example 2 has a protective layer 60 disposed above the dielectric layer 50, and the protective layer 60 is made of a wear-resistant material such as sapphire or glass.

[0053] Please refer to Figure 8, which shows a schematic block diagram of the composite functional capacitive sensing chip of Embodiment 3 of the present invention.

[0054] As shown in Figure 8, Embodiment 3 is largely the same as Embodiment 1, except that Embodiment 1 uses a fingerprint sensing seal, while Embodiment 3 uses a handwriting sensing seal.

[0055] The signal processing circuit layer 20 processes the handwriting image of the pen tip of the writing instrument. Based on the second capacitance value C2(x,y), writing speed v(x,y,t), and writing pressure p(x,y,t) collected by the electrode array layer 40, the handwriting trajectory is reconstructed through a function g that combines speed, pressure, and capacitance changes. The function g adopts the Kalman filter model and satisfies the following relationship function (2): P(x,y,t)=g(C2(x,y,t),v(x,y,t),p(x,y,t)) ----------(2) Where C2(x,y,t) represents the second capacitance value of the electrode array layer measured at time t and position (x, y); v(x, y, t) represents the writing speed of the pen tip at time t and position (x, y); and p(x, y, t) represents the writing pressure applied by the pen tip at time t and position (x, y).

[0056] The feature extraction of the handwriting trajectory includes analyzing the pressure, speed, direction or turning point of the writing to generate a signature verification handwriting trajectory; the reconstruction of the handwriting trajectory is based on the path map generated by the change of a second capacitance value, and the thickness, pressure and / or speed of the writing are analogized to the change of the second capacitance value.

[0057] Please refer to Figure 9, which shows the structural diagram of the sensing matrix of the composite functional capacitive sensing chip of Embodiment 3 of the present invention.

[0058] As shown in Figure 9, NSEL1, NSEL2, NSEL3, NSEL4, FSEL1, FSEL2, FSEL3, and FSEL4 represent the linear selection signals, controlling which linear path (1~32) is selected. The black and red dots represent the control switches corresponding to the control lines. The black box indicates a permanent physical connection on the panel. RX1 to RX8 represent the receiving channel for the sensing signal; the sensor driver integrated circuit connected to this receiving channel records signal changes. By changing the values ​​of the control signals NSEL1, NSEL2, NSEL3, NSEL4, FSEL1, FSEL2, FSEL3, and FSEL4, both general fingerprint reading mode and stylus mode are achieved.

[0059] Figure 9 illustrates the image reading operation logic in pen mode, showing the data processing method when the sensing chip enters a fast mode to process image data input by the pen. This fast mode is designed to improve image reading speed, especially during rapid writing or signing. When the panel enters fast mode, the image reading from the receiving channel undergoes "partial selection" to accelerate data processing. Specifically, partial selection involves reading image data only every 4 or 5 columns; that is, not every column of image data is read, but some columns are skipped to reduce the total amount of data.

[0060] Secondly, while a complete image would normally contain data from all columns, in this fast mode, the controller only processes a portion of the data—1 / 4 or 1 / 5 of the image—significantly reducing the amount of data read. When the data volume is reduced by 1 / 4 or 1 / 5, the total reading time for each image decreases accordingly, assuming the controller's reading speed remains constant. Therefore, the controller can process the entire image faster, thus improving the overall system's responsiveness. In pen mode, to accelerate image reading, the composite-function capacitive sensing chip 1 selects only a portion of the columns (every 4 or 5 columns) instead of reading the entire image. This reduces the amount of data processed, shortening image reading and processing time, resulting in a faster response, making it particularly suitable for scenarios requiring high-speed input, such as signing or rapid writing.

[0061] 1: Composite functional capacitive sensing chip 10:Substrate 12: Internal Circuitry 121: Clock Generator 122: Receiver / Sensor Unit 1220: Switch 1221: Amplifier Circuit 1222: Filtering circuit 1223: A / D Conversion Circuit 1224: Feature Extraction Circuit 1225: Amplifier 1226: Feedback Capacitor 123: Transmission Sensing Unit 124: Signal buffer unit 125: Signal transmission element 126: Electronic devices 20: Signal Processing Circuit Layer 30: Interconnection layer 40: Electrode array layer 41: Primitive 50: Dielectric layer 60: Protective layer

Claims

1. A composite-functional capacitive sensing chip, which is a capacitive sensing and recognition device having at least multiple functions such as fingerprint recognition, electronic signature, and writing trajectory (handwriting) recognition, the composite-functional capacitive sensing chip comprising: A substrate is made of materials such as glass, quartz, silicon oxide, ceramic, or polymer; a signal processing circuit layer is disposed above the substrate for extracting a fingerprint feature and / or a handwriting feature; an interconnect layer is electrically coupled to the signal processing circuit layer and used to transmit a capacitive signal, the interconnect layer being made of at least one metal or a metal-containing material selected from copper, aluminum, gold, silver, alloys, and combinations thereof; An electrode array layer electrically coupled to the interconnect layer includes a plurality of electrodes arranged in a plurality of matrix arrays, each of the plurality of electrodes being composed of at least one metal or a metal-containing material selected from copper, aluminum, gold, silver, alloys, and combinations thereof, and used to sense a capacitance value change function caused by a temporal action of a contact object relative to the electrode array layer, thereby obtaining a fingerprint, writing trace (handwriting or text), and / or the electronic signature; and a dielectric layer electrically coupled to the electrode array layer and used to isolate the electrodes, prevent short circuits, and enhance the capacitance effect, the dielectric layer having a serrated microstructure and formed of a dielectric material with a high dielectric constant, a varistor material, or an insulating material; wherein the contact object is at least one selected from a biological individual's finger, palm, toe, electronic pen, writing instrument, and combinations thereof; The timing action includes: the contact object approaching or touching the electrode array layer; the contact object being stationary, remaining stationary, or held on the electrode array layer; or the contact object performing a movement, motion, or travel action on the electrode array layer; each electrode array further includes at least one varactor capacitor, the capacitance value of which varies from 1fF to 10fF; the signal processing circuit layer is able to generate digital information representing a fingerprint pattern and a stroke trajectory based on parameters such as capacitance value, writing speed, and writing pressure, combined with a specific algorithm.

2. The composite-function capacitive sensing chip as described in claim 1, wherein the signal processing circuit layer processes a fingerprint image of the finger fingerprint, and converts a first capacitance value C1(x,y) acquired by the electrode array layer into the gray value I(x,y) of the corresponding primitive through a gray-scale mapping function f, wherein the gray-scale mapping function f adopts a linear function form and satisfies the following relationship function (1): I(x,y)=f(C1(x,y)) ----------(1); where C1(x,y) represents the first capacitance value measured by the electrode array layer at position (x, y); I(x,y) refers to the gray value of the primitive at position (x, y), representing the brightness of the image at (x, y).

3. The composite-function capacitive sensing chip as described in claim 1, wherein the signal processing circuit layer processes a handwriting image of a pen tip, and reconstructs the handwriting trajectory based on a second capacitance value C2(x,y), a writing speed v(x,y,t), and a writing pressure p(x,y,t) acquired by the electrode array layer, through a function g combining speed, pressure, and capacitance changes, wherein the function g adopts a Kalman filter model and satisfies the following relationship function (2): P(x,y,t)=g(C2(x,y,t),v(x,y,t),p(x,y,t)) ----------(2); where C2(x,y,t) represents the second capacitance value measured by the electrode array layer at time t and position (x,y); v(x,y,t) represents the writing speed of the pen tip at time t and position (x,y); p(x,y,t) represents the writing speed of the pen tip at time t and position (x,y). The writing pressure applied to y).

4. The composite functional capacitive sensing chip as described in claim 2, wherein the fingerprint pattern feature extraction includes extracting the ridge bifurcation points and termination points in the fingerprint image, the fingerprint image is generated as a grayscale image based on the change of the first capacitance value, the area with a larger first capacitance value corresponds to the ridge of the fingerprint, and the area with a smaller capacitance value corresponds to the valley of the fingerprint.

5. The composite functional capacitive sensing chip as described in claim 3, wherein the feature extraction of the handwriting trajectory includes analyzing the pressure, speed, direction or turning point of the writing to generate a signature verification handwriting trajectory; the reconstruction of the handwriting trajectory is based on the path map generated by the change of the second capacitance value, and the thickness, pressure and / or speed of the writing are analogized to the change of the second capacitance value.

6. The composite functional capacitive sensing chip as described in claim 1 further includes a protective layer disposed above the electrode array layer, which is made of a wear-resistant material such as sapphire or glass.

7. The composite functional capacitive sensing chip as described in claim 1 further includes an electronic device electrically coupled to the signal processing circuit layer, which displays a fingerprint or handwriting recognition status information based on a received control signal.

8. The composite functional capacitive sensing chip as described in claim 1, wherein the electrode array layer adopts at least one of a row-column structure, a curved structure, a microchannel structure, a microsphere array structure, or an irregular arrangement structure to improve sensing accuracy and the resolution of a fingerprint image.

9. The composite functional capacitive sensing chip as described in claim 1, wherein the signal processing layer employs at least one of wavelet transform or deep learning algorithm for comparing and analyzing extracted fingerprint features.

10. The composite functional capacitive sensing chip as claimed in claim 7, wherein the electronic device is a microdisplay built into the composite functional capacitive sensing chip or an externally connected device.

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