Fingerprint sensing method, electronic module and computing device

Abstract

A fingerprint sensing method, an electronic module and a computing device. The fingerprint sensing method is applied to the electronic module, which is capable of performing fingerprint sensing and is used to couple to a plurality of fingerprint sensing pixels, and the electronic module includes an analog front-end stage for coupling to the fingerprint sensing pixels. The method includes the following steps: performing a first scanning operation on at least a first part of the fingerprint sensing pixels by using a first reference signal applied to a reference terminal of the analog front-end stage to obtain a magnitude of a second reference signal different from the first reference signal based on a sensing result of the first scanning operation; and performing a second scanning operation on at least a second part of the fingerprint sensing pixels by using a second reference signal applied to the reference terminal of the analog front-end stage.

Description

Technical Field

[0001] The present invention relates to a technology for performing fingerprint sensing in a computing device, and more particularly to a fingerprint sensing method of an electronic module capable of performing fingerprint sensing using dynamic reference signal adjustment, an electronic module capable of performing fingerprint sensing, and a computing device using the electronic module. Background Art

[0002] For computing devices such as smartphones, tablets or other information processing devices, fingerprint sensing has become a standard feature of the computing devices to meet the emerging needs of enhancing security in various applications such as fingerprint recognition in unlocking the computing devices.

[0003] Some available electronic devices, such as smartphones, provide fingerprint sensing functionality on the display panel of the computing device, so that the user can unlock the computing device by placing a finger directly on the display panel. In order to implement the functionality, it is necessary to implement a fingerprint sensing element that corresponds to at least a portion of the display panel of the computing device. If the fingerprint sensing element is designed to correspond to a larger portion or even the entire display panel, a longer signal reading line is required to couple to the fingerprint sensing element. The parasitic capacitance of the signal reading line will also become larger. The analog front-end circuit used to read the fingerprint sensing signal from the fingerprint sensing element through the signal reading line will be susceptible to time delay due to the parasitic capacitance. In this case, the effectiveness and efficiency of fingerprint sensing will inevitably decrease. Therefore, it is also challenging to implement the fingerprint sensing function on the full screen of the display panel. In particular, the time required to sample the fingerprint sensing signal becomes longer, and unfortunately, the time allowed for processing the fingerprint sensing signal is limited. Summary of the invention

[0004] The purpose of the present disclosure is to provide a technique for facilitating fingerprint sensing signal sampling in a computing device. The technique is used to perform dynamic reference signal adjustment in an electronic module capable of fingerprint sensing signal sampling. By using the technique, the electronic module capable of fingerprint sensing signal sampling can dynamically perform reference signal adjustment, thereby reducing the settling time of the analog front-end circuit of the electronic module.

[0005] In order to at least achieve the above-mentioned purpose, the present disclosure provides a fingerprint sensing method, which is applied to an electronic module capable of fingerprint sensing, the electronic module is used to couple to a fingerprint sensor having multiple fingerprint sensing pixels, the electronic module includes an analog front-end stage for coupling to the multiple fingerprint sensing pixels, the method includes: performing a first scanning operation on at least a first part of the multiple fingerprint sensing pixels by using a first reference signal applied to a reference end of the analog front-end stage to obtain the size of a second reference signal based on the sensing result of the first scanning operation; and performing a second scanning operation on at least a second part of the multiple fingerprint sensing pixels by using the second reference signal applied to the reference end of the analog front-end stage, wherein the second reference signal is different from the first reference signal.

[0006] In some embodiments, the second portion includes the first portion.

[0007] In some embodiments, the second portion corresponds to a fingerprint sensing area, and the first portion corresponds to a representative area of ​​the fingerprint sensing area.

[0008] In some embodiments, the first scanning operation includes reading a sensing signal from at least one fingerprint sensing pixel located in a representative area of ​​the fingerprint sensing area, and the second scanning operation includes reading a sensing signal from all fingerprint sensing pixels corresponding to the fingerprint sensing area.

[0009] In some embodiments, the method further includes: performing a reset operation before the first scanning operation.

[0010] In some embodiments, the method further includes: obtaining a magnitude of a third reference signal through the second scanning operation; and performing a third scanning operation on at least a second portion of the plurality of fingerprint sensing pixels by using the third reference signal applied to a reference terminal of the analog front-end stage, wherein the third reference signal is different from the second reference signal.

[0011] In some embodiments, the first portion is equal to the second portion.

[0012] In some embodiments, each of the first portion and the second portion corresponds to a fingerprint sensing area.

[0013] In some embodiments, the first scanning operation includes reading sensing signals of all fingerprint sensing pixels corresponding to the fingerprint sensing area; and the second scanning operation includes reading sensing signals of all fingerprint sensing pixels corresponding to the fingerprint sensing area.

[0014] In some embodiments, the method further includes: performing a reset operation before the first scanning operation; and performing a reset operation before the second scanning operation.

[0015] In some embodiments, the method further comprises determining a magnitude of the second reference signal based on an average of a plurality of fingerprint sensing values ​​resulting from execution of the first scanning operation and a magnitude of the first reference signal.

[0016] In some embodiments, the magnitude of the second reference signal is equal to the magnitude of the first reference signal minus an average value of the plurality of fingerprint sensing values.

[0017] In some embodiments, the analog front end stage comprises an operational amplifier having an input terminal, the input terminal serving as a reference terminal for the analog front end stage.

[0018] In some embodiments, the second reference signal is determined so as to reduce a convergence time of the operational amplifier.

[0019] In some embodiments, the method further includes: determining an average value of a plurality of fingerprint sensing values ​​resulting from execution of the first scanning operation; and determining a magnitude of the second reference signal based on the average value of the plurality of fingerprint sensing values.

[0020] In some embodiments, the magnitude of the second reference signal is equal to the magnitude of the first reference signal minus an average value of the plurality of fingerprint sensing values.

[0021] In order to at least achieve the above-mentioned purpose, the present disclosure provides an electronic module capable of fingerprint sensing and used to be coupled to a fingerprint sensor having a plurality of fingerprint sensing pixels, the electronic module comprising a fingerprint sensing driver circuit. The fingerprint sensing driver circuit comprises: a fingerprint sensing circuit and a control unit. The fingerprint sensing circuit is used to couple to the fingerprint sensor and obtain fingerprint sensing data, and comprises an analog front-end stage. The control unit is coupled to the fingerprint sensing circuit and used for fingerprint sensing, wherein the control unit is configured to perform a plurality of operations. The plurality of operations include: performing a first scanning operation on at least a first part of the plurality of fingerprint sensing pixels by using a first reference signal applied to a reference terminal of the analog front-end stage to obtain a size of a second reference signal based on a sensing result of the first scanning operation; and performing a second scanning operation on at least a second part of the plurality of fingerprint sensing pixels by using the second reference signal applied to the reference terminal of the analog front-end stage, wherein the second reference signal is different from the first reference signal.

[0022] In some embodiments, the control unit is further configured to obtain a touch position on the touch panel, wherein the first scanning operation is performed on the first portion with respect to the touch position.

[0023] In order to at least achieve the above objective, the present disclosure provides a computing device, comprising: a display panel having a fingerprint sensor; and an electronic module coupled to the display panel and capable of fingerprint sensing.

[0024] In some embodiments, when appropriate, the electronic module may be configured to implement any one of the above embodiments or a combination of at least two or more thereof.

[0025] In some embodiments, the electronic module is a single chip.

[0026] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, such description and drawings are only used to illustrate the present invention and are not intended to limit the scope of rights of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1A A display panel having a fingerprint sensor and a fingerprint sensing driver circuit according to various embodiments are shown in schematic form;

[0028] Figure 1B is a block diagram showing implementation of fingerprint sensing in a computing device according to an embodiment;

[0029] Figure 1C is a block diagram showing an electronic module capable of performing fingerprint sensing in a computing device according to an embodiment;

[0030] Figure 1D is a block diagram showing an electronic module capable of performing fingerprint sensing in a computing device according to another embodiment;

[0031] Figure 1E is a block diagram showing an electronic module capable of performing fingerprint sensing in a computing device according to another embodiment;

[0032] Figure 1F is a flow chart showing a method for fingerprint sensing according to an embodiment;

[0033] Figure 2A is a schematic diagram of the panel and readout IC showing resetting the panel photodiode voltage;

[0034] Figure 2B is a schematic diagram of a panel and a readout IC, which shows the first sampling of a correlated double sampling (CDS);

[0035] Figure 2C is a schematic diagram of the panel and readout IC, which illustrates the second sampling and subtraction readout of the CDS;

[0036] Figure 3 is a schematic block diagram of a feedback loop for second sampling;

[0037] Figure 4 It is a schematic diagram of the light and dark distribution of fingerprints;

[0038] Figure 5 shows the relationship between the number of time constants required for convergence (N) and the final gap voltage (LSB);

[0039] Fig. 6A shows an example of loop operation during a reset phase;

[0040] Figure 6B An example of loop operation in readout phase 1 is shown;

[0041] Figure 6C An example of loop operation in readout phase 2 is shown;

[0042] Figure 7 A flowchart showing an implementation example of a reference voltage adjustment mechanism of a CDS;

[0043] Figure 8 A flow chart showing another implementation of a reference voltage adjustment mechanism of a CDS;

[0044] Fig. 9 A schematic diagram showing the implementation of the readout architecture of the panel and readout IC;

[0045] Fig.10 A flow chart illustrating an implementation of a plurality of CDS reference voltage adjustment readout processes is shown;

[0046] Fig.11 The implementation of the pixel voltage prediction method is shown;

[0047] Fig. 12A shows an example of loop operation in readout phase 1; and

[0048] Fig. 12B An example of loop operation in readout phase 2 is shown.

[0049] Reference numerals:

[0050] 1 Computing device

[0051] 5 Processing Unit

[0052] 9 Display Panel

[0053] 10 Electronic modules

[0054] 11 Fingerprint sensing driver circuit

[0055] 12 Display driver circuit

[0056] 19 Touch driver circuit

[0057] 21 First Chip

[0058] 22 Second chip

[0059] 90 substrate

[0060] 91 Fingerprint sensor array

[0061] 92 display pixel array

[0062] 99 Touch Sensing Array

[0063] 110 Fingerprint sensing circuit

[0064] 112 Control unit

[0065] 115 Memory

[0066] 900 CDS Reference Level Processing Unit

[0067] 1100 Area

[0068] OP, OP1~OPX front-end amplifier

[0069] 10A Electronic Module

[0070] 10B Electronic Module

[0071] 10C Electronic Module

[0072] 1A Computing Device

[0073] 1B Computing Device

[0074] 1C Computing Device

[0075] 9A Display Panel

[0076] ADC analog-to-digital conversion circuit

[0077] AFE Analog Front End Circuit

[0078] Cd Storage Capacitor

[0079] Cf, Cf1~CfX Feedback capacitor

[0080] Cpar parasitic capacitance

[0081] CT Center

[0082] FR Finger

[0083] FSA Fingerprint Sensing Area

[0084] ICN pattern

[0085] PD Photodiode

[0086] S10, S20 steps

[0087] S1010~S1200 Steps

[0088] S710~S780 Steps

[0089] Steps S810 to S890, S892, S894

[0090] Sout routing

[0091] Sout1~SoutX routing

[0092] Sr, Sr1~SrX feedback switch

[0093] Sw1~SwY pixel switch

[0094] Vexpa Average exposure voltage

[0095] Vexpd The difference between the fingerprint pixel and the average finger center

[0096] Vo1~VoX voltage difference

[0097] Vo1n~VoXn sampling voltage

[0098] Vo1p~VoXp sampling voltage

[0099] Vofs Bias voltage

[0100] Vrst reset voltage

[0101] Vs11, Vs12~Vs1Y voltage

[0102] Vsout1~VsoutX voltage signal

[0103] VsX1, VsX2~VsXY voltage

[0104] Vx voltage difference

[0105] Fingerprint detection section (1,1) to fingerprint detection section (M,N) Fingerprint detection section DETAILED DESCRIPTION

[0106] In order to facilitate understanding of the purpose, features and effects of the present disclosure, multiple embodiments of the present disclosure are provided in detail with reference to the accompanying drawings.

[0107] Various embodiments of techniques for facilitating enhanced fingerprint sensing efficiency in a computing device are provided below. The techniques are used to dynamically adjust a reference signal in an electronic module with a fingerprint sensing function. Using the techniques, the electronic module with a fingerprint sensing function can dynamically adjust the reference signal to improve the quality of the fingerprint image output by the electronic module.

[0108] For illustration, in the following, firstly, an embodiment of an electronic module capable of performing fingerprint sensing and a computing device (or device) using the electronic module is introduced. Then, an embodiment of a method for dynamic reference signal adjustment in an electronic module capable of performing fingerprint sensing is provided. Then, further provided are an embodiment of an electronic module capable of performing fingerprint sensing and an embodiment of a computing device (or device) using the electronic module.

[0109] Figure 1A Schematically shows a computing device according to an embodiment, the computing device includes an electronic module 10 capable of performing fingerprint sensing and a display panel 9 having a fingerprint sensor coupled to the electronic module 10. Please refer to Figure 1B , shows an electronic module 10 capable of performing fingerprint sensing, which can be used in a computing device 1. Figure 1B As shown, the computing device 1 includes a processing unit 5, an electronic module 10, and a fingerprint sensor, wherein the electronic module 10 includes a fingerprint sensing driver circuit 11, and the fingerprint sensor includes a fingerprint sensing array 91. The electronic module 10 can be coupled between the fingerprint sensing array 91 and the processing unit 5 to perform fingerprint sensing. The electronic module 10 can be configured to perform a method for dynamic reference signal adjustment in an electronic module capable of fingerprint sensing, which will be described later. Figure 1F Examples are given in the following sections.

[0110] based on Figure 1A and 1B The architecture of the computing device 1 shown in the figure can implement any electronic device, such as a smart phone, a tablet computer or any other information processing device, wherein the computing device 1 may further include but is not limited to: additional components such as a memory (as represented by 115), circuits for wireless or wired communication, image acquisition circuits, or the like, as long as they are appropriate.

[0111] The processing unit 5 can be configured to receive fingerprint data from the electronic module 10 to provide a specific function. For example, the processing unit 5 executes an application based on fingerprint recognition, for example, under an operating system, to obtain fingerprint image data derived from a signal obtained from the fingerprint sensing array 91 by the electronic module 10. The computing device 1 (e.g., a smartphone, a tablet computer, etc.) can be configured to perform multiple operations of the application (e.g., user operations or functions in a game), which are associated with the fingerprint image data generated by the electronic module 10.

[0112] Reference Figure 1A and Figure 1B , the fingerprint sensing driver circuit 11 can be used to couple to the fingerprint sensing array 91 and obtain fingerprint sensing data from the signal from the fingerprint sensing array 91. For example, the fingerprint sensing array 91 is implemented to include: a plurality of fingerprint sensing elements (or referred to as sensing pixels), and the plurality of fingerprint sensing elements are arranged on a fingerprint sensing area (FSA). For example, the fingerprint sensing driver circuit 11 is implemented to convert the fingerprint signal received from the fingerprint sensing array 91 into corresponding digital fingerprint data, such as being associated with and distributed in the fingerprint sensing area FSA (such as Figure 1A A set of raw fingerprint data on the display panel 9 (as shown in FIG. 1B or FIG. 1B ). Fingerprint data can be further obtained based on the digital fingerprint data, for example, by the fingerprint sensing driver circuit 11. In addition, the fingerprint sensing area FSA can be implemented as at least a portion of the screen of the display panel 9 corresponding to where the finger (FR) can be placed, or can be implemented as the entire screen of the display panel 9.

[0113] For example, the electronic module 10 may be implemented as a chip. Figure 1C As shown in FIG. 1 , the display driver circuit 12 and the touch driver circuit 19 may be implemented as a single chip to integrate and include the display driver circuit 12 and the touch driver circuit 19 in addition to the fingerprint sensing driver circuit 11. Figure 1CAs shown, the display driver circuit 12 and the touch driver circuit 19 are respectively coupled to the display pixel array 92 and the touch sensing array 99 of the display panel 9A. In this way, the electronic module (e.g., 10 or 10A) can be referred to as a fingerprint, touch, display driver integration (fingerprint, touch, display driver integration, FTDI) chip (IC). The electronic module 10 can be implemented as an FTDI chip disposed on a substrate 90 (e.g., glass or film, etc.), for example, by using a packaging method such as a tape carrier package (TCP), a chip on film (COF) or a chip on glass (COG).

[0114] like Figure 1B As shown, the fingerprint sensing driver circuit 11 may include a fingerprint sensing circuit 110 and a control unit 112 for fingerprint sensing. For example, the fingerprint sensing circuit 110 may include a fingerprint analog front end (AFE) circuit and an analog-to-digital converter (ADC) circuit to convert a fingerprint signal received from the fingerprint sensing array 91 into corresponding digital fingerprint data. The digital fingerprint data is, for example, a set of raw fingerprint data, which is associated with and distributed on a fingerprint sensing area FSA, where a fingerprint (or a part of a fingerprint) is detected in the fingerprint sensing area FSA. Fingerprint sensing data may be further obtained based on the digital fingerprint data, for example, by the control unit 112. The control unit 112 coupled to the fingerprint sensing circuit 110 may be used for fingerprint sensing, for example, to generate fingerprint sensing data based on the digital fingerprint data.

[0115] Please refer again Figure 1A and Figure 1B , to illustrate the effect of the offset in the signal received by the electronic module 10. In the example, the fingerprint detection process involves the operation of the display panel 9 and the electronic module 10. Initially, the user places his finger on the fingerprint sensing area FSA to make a touch event on the display panel 9. The touch position associated with the touch event can be detected by a touch driver circuit to output the touch position, wherein the touch driver circuit can be implemented inside the electronic module, such as Figure 1CAs shown, or it can also be implemented outside the electronic module. The electronic module (such as 10 or 10A) activates at least one fingerprint detection section of the fingerprint sensing area FSA according to the touch position output by the touch driver circuit (such as 19) to start fingerprint sensing, and then enters the fingerprint detection process. The fingerprint detection process, for example, includes: controlling the display panel (such as 9 or 9A) to emit light to the touch position where the finger is placed; receiving a voltage signal, wherein the voltage signal is converted by the fingerprint sensing element of the fingerprint sensing array 91 from the reflected light of the fingerprint ridge and valley; amplifying the received voltage signal and performing analog-to-digital conversion, which is performed by the AFE circuit and ADC circuit of the electronic module (such as 10 or 10A) respectively; and outputting the fingerprint image data (for example, data representing the entire fingerprint image) to the processing unit 5, and executing the back-end algorithm for fingerprint recognition. Therefore, the unlocking process of the computing device (such as 1, 1A, 1B or 1C) can be performed and completed based on fingerprint recognition.

[0116] Please refer to Figure 1A , the fingerprint sensing elements (or fingerprint sensing pixels) of the fingerprint sensing array 91 can be distributed over the entire screen of the display panel 9, so that a computing device can be implemented to allow a user to unlock the computing device at any position on the screen. For example, the fingerprint sensing area FSA can be substantially equal to the range of the screen (such as exactly equal to, slightly different from, or within a tolerable range to facilitate full-screen fingerprint sensing of the panel). In full-screen fingerprint sensing applications, the fingerprint sensing area FSA or the screen can be divided into different fingerprint detection sections (for example, represented by fingerprint detection section (1,1) to fingerprint detection section (M,N)), so that fingerprint recognition can be performed for the fingerprint detection section where the finger (FR) is placed.

[0117] In some embodiments, Figure 1A , 1B The electronic modules shown in 10 or 10A are implemented in a single chip, thereby resulting in many benefits of circuit integration to the computing device 1. Figure 1D , which shows that based on Figure 1A , 1B A single chip embodiment of the configuration of an electronic module (e.g., 10 or 10A) of an IC or 1C. Figure 1D As shown, the electronic module 10B is implemented in a single chip form, applied in a computing device 1B, and includes a fingerprint sensing driver circuit 11 and a touch driver circuit 19. The electronic module 10B may also include a display driver circuit 12 for connecting to a display pixel array (eg, 92).

[0118] It should be noted that, in some embodiments, the electronic module 10 can be implemented using multiple chips according to design requirements. Figure 1A , 1B, 1C, or 1D, the electronic module (e.g., 10 or 10A) shown is implemented in a single chip. For example, in some embodiments, the touch driver circuit and the fingerprint sensing driver circuit are implemented as different chips. Figure 1E In one embodiment shown, the electronic module 10C is used in a computing device 1C and includes a first chip 21 and a second chip 22. The first chip 21 includes a fingerprint sensing driver circuit 11, and the second chip 22 includes a touch driver circuit 19. The first chip 21 may also include a display driver circuit 12 for connecting to a display pixel array (e.g., 92) to drive the display pixel array. Of course, the embodiments of the present disclosure are not limited thereto.

[0119] about Figures 1A to 1E The hardware structure of the elements in any embodiment of the present invention, the fingerprint sensing driver circuit (e.g., 11), the display driver circuit (e.g., 12) and the touch driver circuit (e.g., 19) can be implemented based on a control circuit individually or integratedly, and the control circuit includes a microcontroller-based or processor-based core with computing capabilities. In addition, the fingerprint sensing driver circuit (e.g., 11), the display driver circuit (e.g., 12) and the touch driver circuit (e.g., 19) can be designed based on a technique using a hardware description language (HDL) or any other design method of a digital circuit familiar to those skilled in the art, and can be based on a hardware circuit implemented using a field programmable gate array (FPGA), a complex programmable logic device (CPLD) or an application-specific integrated circuit (ASIC).

[0120] In some embodiments, the display pixel array 92 may be a liquid crystal display (LCD) pixel array, an organic light emitting diode (OLED) pixel array, or any suitable type of pixel array. For example, the display panel 9 may be implemented by an "in-cell type" or "on-cell type" touch display panel with integrated fingerprint sensing, wherein the fingerprint sensing array 91, the display pixel array 92, and the touch sensing array 99 are integrated in a layered manner or in any suitable manner. The touch sensing array 99 may be implemented in the form of a capacitive touch sensor. The fingerprint sensing array 91 may be implemented, for example, by an optical fingerprint sensor, a capacitive fingerprint sensor, an ultrasonic fingerprint sensor, or any suitable fingerprint signal sensing device. Of course, the implementation of the present disclosure is not limited thereto.

[0121] An embodiment for performing a fingerprint sensing method will be described below.

[0122] Please refer to Figure 1F, according to an embodiment, a method for performing fingerprint sensing is shown in the form of a flow chart. The method for performing fingerprint sensing can be implemented in an electronic module (e.g., 10) or specifically in a fingerprint sensing driver circuit (e.g., 11), the electronic module is used to be coupled between the fingerprint sensing array 91 and the processing unit 5. The electronic module is used to couple to the fingerprint sensing array 91 having a plurality of fingerprint sensing pixels, and the electronic module includes an analog front-end stage for coupling to the fingerprint sensing pixels. As shown in FIG. Figure 1F As shown, the method comprises the following steps, wherein reference is made to the electronic module 10 for illustration purposes only.

[0123] In step S10, a first scanning operation is performed on at least a first portion of fingerprint reference pixels by applying a first reference signal to a reference terminal of an analog front end stage to obtain a magnitude of a second reference signal based on a sensing result of the first scanning operation.

[0124] In step S20 , a second scanning operation is performed on at least a second portion of the fingerprint sensing pixels by applying a second reference signal to a reference terminal of the analog front end stage, wherein the second reference signal is different from the first reference signal.

[0125] therefore, Figure 1F It is used for dynamic reference signal adjustment in the electronic module capable of sampling the fingerprint sensing signal. Figure 1F According to the method, an electronic module capable of sampling a fingerprint sensing signal can dynamically adjust a reference signal to reduce the setup time of an analog front-end circuit of the electronic module.

[0126] In addition, based on the dynamic reference signal adjustment technology, the time required for sampling the fingerprint sensing signal can be reduced, and the fingerprint sensing signal can be configured to be processed within the allowed time interval, thereby solving the challenge of implementing the fingerprint sensing function on the full screen of the display panel.

[0127] As a result, a computing device that executes an application such as fingerprint recognition based on the output of an electronic module may benefit from techniques for dynamic reference signal adjustment, thereby facilitating the effectiveness and efficiency of fingerprint sensing for the application as a whole.

[0128] In some embodiments, the second portion includes the first portion. For example, the second portion corresponds to a fingerprint sensing area (eg, a touch area corresponding to a fingerprint on a panel or an area determined based on other relevant conditions), and the first portion corresponds to a representative area of ​​the fingerprint sensing area.

[0129] In some embodiments, the first scanning operation includes reading a sensing signal from at least one fingerprint sensing pixel located in a representative area of ​​the fingerprint sensing area, and the second scanning operation includes reading a sensing signal from all fingerprint sensing pixels corresponding to the fingerprint recognition area.

[0130] In some embodiments, the method further includes performing a reset operation before the first scanning operation.

[0131] In some embodiments, the method further includes the following steps: obtaining the magnitude of a third reference signal through a second scanning operation; and performing a third scanning operation on at least a second portion of the fingerprint sensing pixel by applying the third reference signal to a reference terminal of the analog front-end stage, wherein the third reference signal is different from the second reference signal.

[0132] In some embodiments, the first portion is equal to the second portion.

[0133] In some embodiments, each of the first portion and the second portion corresponds to a fingerprint sensing area.

[0134] In some embodiments, each of the first scanning operation and the second scanning operation includes reading sensing signals of all fingerprint sensing pixels corresponding to the fingerprint sensing area.

[0135] In some embodiments, the method further includes performing a respective reset operation prior to each of the first scanning operation and the second scanning operation.

[0136] In some embodiments, the method further includes determining a magnitude of the second reference signal based on an average of a plurality of fingerprint sensing values ​​from execution of the first scanning operation and a magnitude of the first reference signal.

[0137] In some embodiments, the magnitude of the second reference signal is equal to an average of the plurality of fingerprint sensing values ​​subtracted from the magnitude of the first reference signal.

[0138] In some embodiments, the analog front end stage includes an operational amplifier having an input terminal that is used as an analog front end stage (e.g., Figure 1A as shown).

[0139] In some embodiments, the second reference signal is determined to reduce a convergence time of the operational amplifier.

[0140] In some embodiments, the method further includes the following steps: determining an average value of the fingerprint sensing value according to the execution of the first scanning operation; and determining the size of the second reference signal based on the average value of the fingerprint sensing value.

[0141] In some embodiments, the magnitude of the second reference signal is equal to an average of the fingerprint sensing values ​​subtracted from the magnitude of the first reference signal.

[0142] In some embodiments, an electronic module 10 capable of fingerprint sensing can be configured to be coupled to a fingerprint sensor having a plurality of fingerprint sensing pixels. The electronic module 10 includes a fingerprint sensing driver circuit. The fingerprint sensing driver circuit includes a fingerprint sensing circuit and a control unit. The fingerprint sensing circuit is used to couple to the fingerprint sensor and obtain fingerprint sensing data, and includes an analog front-end stage. The control unit coupled to the fingerprint sensing circuit is used for fingerprint sensing. The control unit is configured to perform a plurality of operations. The plurality of operations include performing a first scanning operation on at least a first portion of the fingerprint sensing pixels by using a first reference signal, the first reference signal being applied to a reference terminal of the analog front-end stage to obtain the size of a second reference signal based on the sensing result of the first scanning operation. The plurality of operations also include performing a second scanning operation on at least a second portion of the fingerprint sensing pixels by using a second reference signal applied to the reference terminal of the analog front-end stage, wherein the second reference signal is different from the first reference signal.

[0143] In some embodiments, the control unit is further configured to obtain a touch position on the touch panel, wherein the first scanning operation is performed on the first portion with respect to the touch position.

[0144] The following provides Figure 1F Embodiments of the method shown. Systems, devices and methods for reference voltage adjustment in fingerprint sensing driver circuits or FTDI chips are described.

[0145] The following describes an implementation of a correlated double sampling (CDS) reference voltage adjustment mechanism in a fingerprint sensing driver circuit or an FTDI chip, such as in a computing device (eg, a smart device).

[0146] Generally speaking, correlated double sampling (CDS) is a method of measuring electrical values, such as voltage or current, that eliminates unwanted offsets. This method is often used when measuring sensor outputs. The output of the sensor is measured twice: once under known conditions and once under unknown conditions. The value measured under the known conditions is then subtracted from the value measured under the unknown conditions to produce a value that has a known relationship to the physical quantity being measured. It should be noted that in the following embodiments, modified or specific implementations based on the CDS concept may be used; however, the embodiments of the present disclosure are not limited thereto.

[0147] Refer to Figure 1A, illustrating the process of display panel and FTDI for fingerprint unlocking. For example, during the FTDI fingerprint recognition process, the panel emits light from the light source to the area where the finger is pressed (as represented by the pattern shown in ICN). The light is reflected by the ridges and valleys of the fingerprint and then converted into a sensing signal (such as a voltage signal) by the fingerprint sensing pixels on the panel (such as TFT sensors). The fingerprint sensing signal is then transmitted to FTDI. After amplification and A / D conversion, the entire image data is output to the back-end algorithm for fingerprint recognition, completing the fingerprint unlocking process. Reference Figure 1A , a fingerprint sensing array (such as a TFT sensor array) can be arranged in the entire display panel area, facilitating fingerprint unlocking at any position.

[0148] Since the fingerprint sensor (e.g., fingerprint sensing pixel) is implemented on the entire panel, the wiring for signal readout needs to pass through the entire panel. The wiring for signal readout is long and has high parasitic capacitance, which causes time delay when the AFE reads the sensing signal from the fingerprint sensing pixel (such as the sensing current from the photodiode).

[0149] CDS can be divided into or include at least four stages (or steps). First, Figure 2A As shown, by using a front-end amplifier (such as represented by OP1 to OPX; for simplicity, OP is used to represent a corresponding one of OP1 to OPX) on a readout IC (for example, implemented as a single chip, such as the fingerprint sensing circuit 110 of the fingerprint sensing driver circuit 11), each fingerprint sensing pixel on the display panel 9 is reset. Corresponding to each column (column) of the fingerprint sensing pixel of the display panel 9. Specifically, each feedback switch (for example, Sr1 to SrX) of the front-end amplifier (represented by OP) is turned on so that the output of the front-end amplifier OP can lock the voltage at the reset voltage Vrst, and then the pixel switches Sw1 to SwY are turned on in turn, and turned off after resetting, so that the fingerprint sensing array of the entire panel has a voltage reset to the reset voltage Vrst. Please note that in Figure 2A As in other similar figures, the display panel 9 and the fingerprint sensing circuit 110 are partially represented by two separate boxes, and the boxes shown in the figure have nothing to do with the circuit connection.

[0150] Secondly, after the fingerprint sensing pixel (for example, including a photodiode and a capacitor connected in parallel) is reset to a reset voltage Vrst, the reflected light is different due to the different refractive indices of the light irradiation and contact surface, so that the fingerprint sensing pixel generates its own sensing current (for example, photocurrent), which is stored in the capacitor of the corresponding fingerprint sensing pixel. At the same time, these capacitors have corresponding voltages Vs11, Vs12, ..., Vs1Y~VsXY.

[0151] Third, if Figure 2B As shown, the feedback switches Sr1 to SrX of the front-end amplifier are turned on, but the pixel switches Sw1 to SwY of the fingerprint sensing pixel are not turned on. At this time, the parasitic capacitor Cpar is charged to the reset voltage Vrst, and the two ends of the feedback capacitors Cf1 to CfX are discharged to no voltage difference. Then, the first sampling is performed to obtain the sampled voltages Vo1p to VoXp, each of which is obtained by sampling the offset voltage of the corresponding front-end amplifier OP plus the reset voltage Vrst.

[0152] Fourth, if Figure 2C As shown, the pixel switch (e.g., Sw1) is turned on; since the voltage signal (e.g., Vsout1 to VsoutX) will be locked by the feedback loop of the front-end amplifier at the reset voltage Vrst plus the offset voltage of the front-end amplifier, the pixel exposure charge will be amplified to the output of the front-end amplifier. At the same time, the second sampling is performed to obtain the sampled voltages Vo1n to VoXn, each of which is obtained by sampling the offset voltage of the corresponding front-end amplifier OP plus the reset voltage Vrst plus Qlight / Cf, where Qlight represents the charge amount of the corresponding fingerprint sensing pixel, and Cf represents the feedback capacitance of the corresponding front-end amplifier OP (e.g., Cf represents one of Cf1 to CfX).

[0153] Subtracting the sampling voltage of the first sampling from the sampling voltage of the second sampling can eliminate the offset voltage and the reset voltage Vrst, thereby obtaining the Qlight / Cf values ​​corresponding to multiple fingerprint sensing pixels as the voltage differences Vo1 to Vox. Repeat the above steps three and four (for example, with respect to each column) to complete the fingerprint image reading of the entire panel.

[0154] Figure 3 is a schematic block diagram of the feedback loop of the second sampling, for the sake of simplicity and explanation as Figure 2A Or a circuit similar to the one shown in the figure, Figure 3 The fingerprint sensing pixel is shown coupled to the front-end amplifier through traces. Figure 3 In the embodiment, the fingerprint sensing pixel includes, for example, a photodiode PD and a storage capacitor Cd, or may further include other components, and the front-end amplifier OP has a feedback capacitor Cf and a feedback switch Sr. The parasitic capacitance Cpar of the wiring Sout extending through the display panel is large (for example, on the order of about 50 pF), wherein the wiring Sout can be used to represent Figure 2AOr a corresponding one of the traces Sout1 to SoutX shown in the figure. However, in order to convert the sensed charge of the fingerprint sensing pixel into a voltage signal, the feedback capacitance of the OP is very small (e.g., on the order of about 0.1 pF), and the feedback of the parasitic capacitance Cpar to the feedback capacitance Cf causes the OP bandwidth to be attenuated by tens or hundreds of times (or more times) relative to the unity gain bandwidth (e.g., about 500 times), and the two sampling stages of the CDS require a longer stabilization time.

[0155] It can be seen that in the above case, due to the large parasitic capacitance Cpar, the AFE requires a longer stabilization time. Therefore, in the various embodiments provided below, the reference voltage of the CDS can be adjusted with each exposure voltage so that the two readout voltages of the CDS are similar. By reducing the difference between the two output voltages of the AFE, the required stabilization time can be reduced. Therefore, by adjusting the reference voltage of the CDS, the difference between the two sampled voltages of the CDS can be reduced, and the stabilization time required for the AFE output between samples can be reduced, thereby improving the efficiency of signal acquisition.

[0156] Figure 4 is a schematic diagram of the light and dark distribution of fingerprints. Figure 4 As shown, the difference between light and dark in the ridges and valleys of a fingerprint is small (eg, about 10 mV), but the overall environment is very different (eg, on the order of 1 V).

[0157] Figure 5 The relationship between the number of time constants required for convergence (N) and the final value difference voltage (LSB) is shown to represent the time required for the voltage to converge to 0.5LSB, from which the time required for the AFE to converge between the fingerprint recognition voltage and the reference voltage can be derived. The voltage change required to ensure the output code level change is called the least significant bit (LSB) voltage. Figure 5 As shown, if the average sensing voltage of the fingerprint sensing signal is used as the reference value when the CDS sampling is read out, the voltage difference that needs to be changed when the AFE is read out can be reduced, and the convergence time required for the light and dark difference of the fingerprint pixel can be reduced. In the case of a fixed convergence time, the reading accuracy can also be improved. In this way, the dynamic reference signal adjustment for sampling in fingerprint sensing can promote the effectiveness and efficiency of the fingerprint sensing process. However, the implementation of the present disclosure is not limited to the example of the reference signal value.

[0158] Fig. 6A An example of the operation of the circuit in the reset phase is shown. Fig. 6A In the operation of the reset phase shown, the desired reset voltage is output to the photodiode PD via OP, and since OP has a bias voltage (such as represented by Vofs), it resets the voltage to Vrst+Vofs.

[0159] Vexpa is the average exposure voltage of at least a portion of the area where the fingerprint is detected (eg, the center of the fingerprint or a reduced portion including the center), and Vexpd is the difference between the fingerprint pixel and the average finger center.

[0160] Figure 6B An example of the operation of the loop in the readout phase 1 is shown. For example, Figure 6B As shown, during CDS phase 1, Vrst-Vexpa (where a preset value is used) is applied to the non-inverting terminal of OP so that the first reading performed by CDS after feedback can obtain Vrst+Vofs-Vexpa as the first reading voltage.

[0161] Figure 6C An example of the operation of the loop in the read phase 2 is shown. The second read of the CDS reads the exposure voltage Vrst+Vofs-Vexpa-Vexpd, and through the feedback of the OP, a portion of Vexpd is read and amplified to the OP output, and the second sampled voltage of the CDS is Vrst+Vofs-Vexpa+Vexpd (Cd / Cf). Between the two samples, the voltage difference of the OP output is represented by Vexpd (Cd / Cf). Since the average value of the finger center and the voltage difference between the fingerprint pixels are small, the OP only needs a short time to stabilize.

[0162] Figure 7 An illustrative flow chart showing an implementation example of a process of the FTDI CDS reference voltage adjustment mechanism. In step S710, a touch position on the touch panel is obtained, the touch position being considered as a representative position or a representative area of ​​the fingerprint sensing area (e.g., the center of the fingerprint). In step S720, the fingerprint sensing pixel is reset. In step S730, a pixel exposure voltage is sampled relative to the representative position or the representative area. In step S740, the sampled pixel exposure voltage is determined to obtain a determined exposure voltage. In step S750, a reference signal applied to a reference terminal (e.g., a non-inverting terminal) of an analog front end stage (e.g., OP) is set to the determined exposure voltage. In step S760, the readout switch of the next row is turned on. In step S770, it is determined whether the fingerprint image readout is completed. If yes, the fingerprint reading is completed as shown in step S780. If not, the process is repeated starting from step S760.

[0163] like Figure 7As shown, an example of the process includes a pre-scanning step (or process) and a normal reading step. In the example, after the panel touch control unit (e.g., a touch driver circuit (such as 19) implemented in a single chip such as FTDI) reports the finger position, a representative area or representative position (e.g., center) of the fingerprint or a position representing the exposure of the finger is sampled and read out. After calculating the voltage relative to the position, the voltage is provided to the positive electrode (non-inverting end) of the OP as a reference voltage. By setting the voltage, the entire finger image is read in sequence to shorten the image reading convergence time of the AFE.

[0164] Figure 8 A flow chart showing another implementation of the FTDI CDS reference voltage adjustment mechanism. In step S810, a touch position on the touch panel is obtained, which is used as a representative position or representative area of ​​the fingerprint sensing area (e.g., the center of the fingerprint). In step S820, the fingerprint sensing pixels are reset. In step S830, the readout switches of the next row are turned on. In step S840, it is determined whether the fingerprint image readout is complete. If so, the fingerprint reading is completed as shown in step S850. If not, the process is repeated starting from step S830.

[0165] In step S860, the sampled pixel exposure voltage is determined to obtain a determined exposure voltage. In step S870, a reference signal applied to a reference terminal (e.g., a non-inverting terminal) of an analog front end stage (e.g., OP) is set to the determined exposure voltage. In step S880, the fingerprint sensing pixel is reset.

[0166] In step S890, the readout switch of the next row is turned on. In step S892, it is determined whether the fingerprint image readout is complete. If so, the fingerprint reading is complete as shown in step S894. If not, the process is repeated starting from step S890.

[0167] like Figure 8 As shown, the implementation example of the process includes a first reading (first image reading) step and a second reading (second image reading) step. In this example, the fingerprint image is read once (first image reading), and then the operation unit calculates the appropriate CDS reference voltage, which is then applied to the non-inverting terminal of the OP as a reference voltage.

[0168] Fig. 9The circuit architecture of the panel CDS reference level adjustment mechanism is shown. For example, a representative position or a representative area of ​​the fingerprint (e.g., a position at or near the center of the fingerprint) is first selected, and a reference signal required relative to the representative position or the representative area is determined by using the CDS reference level processing unit 900 of the readout IC (e.g., implemented by a control unit of a fingerprint sensing driver circuit of a single chip). The determined reference signal is applied to the AFE as a reference voltage to help reduce the convergence time required for the AFE to perform CDS.

[0169] Fig.10 Schematic flow chart showing an implementation example of a multi-CDS reference voltage adaptive readout process.

[0170] In step S1010, a touch position on the touch panel is obtained, and the touch position is regarded as a representative position or a representative area of ​​the fingerprint sensing area (e.g., the center of the fingerprint). In step S1020, the fingerprint sensing pixel is reset. In step S1025, the fingerprint sensing pixel is exposed. In step S1030, the pixel exposure voltage is sampled relative to the representative position or the representative area. In step S1040, the sampled pixel exposure voltage is determined to obtain a determined exposure voltage. In step S1050, a reference signal applied to a reference terminal (e.g., a non-inverting terminal) of an analog front-end stage (e.g., OP) is set to the determined exposure voltage. In step S1060, the readout switch of the next row is turned on. In step S1070, it is determined whether the fingerprint image readout is completed. If so, as shown in step S1080, one round of reading is completed. If not, the process is repeated starting from step S1060.

[0171] In step S1100, it is determined whether the fingerprint image needs to be read again according to the judgment criteria. If yes, the method proceeds to step S1110; if no, the fingerprint reading is completed as shown in step S1200. For example, the judgment criteria can be a loop condition (while-looping) based on a threshold value so as to repeat the fingerprint image reading multiple times, so that an accurate fingerprint image can be determined based on multiple fingerprint images. In another example, the judgment criteria can be other conditions based on one or more factors.

[0172] In step S1110, the fingerprint sensing pixel is reset. In step S1120, the fingerprint sensing pixel is exposed. In step S1130, the updated (or same) reference signal is applied to the reference terminal (eg, non-inverting terminal) of the analog front end stage (eg, OP).

[0173] In this embodiment, if Fig.10As shown, in order to avoid the interference of dirt or noise on the finger and affect the accuracy of pre-reading, the exposure and fingerprint image reading can be performed by adjusting Vref multiple times (such as pre-scanning) to obtain an optimized fingerprint image, or the fingerprint features of multiple images can be combined to generate a more accurate fingerprint image. Fig.10 As shown, after reading relative to a representative position or a representative area (e.g., the center) of the fingerprint, a reference voltage Vref can be generated for the first time according to the brightness of the representative position or the representative area of ​​the fingerprint to achieve image reading. The first reference voltage Vref generated in this way is added to Vd to adjust the reference voltage. After the reference voltage is adjusted, exposure and image reading are performed again to obtain a readout image. Then, the image is sent to a processing unit (or application) for judgment and adjustment.

[0174] For example, the voltage magnitude of Vd may not only be variable, but also be positive and / or negative, for reference voltage adjustment, thereby achieving multiple exposures and fingerprint image reading. In some examples, in order to achieve multiple exposures and fingerprint image reading, the voltage magnitude of Vd may be set to multiple values ​​for reference voltage adjustment, thereby achieving multiple exposures and fingerprint image reading. In another example, the magnitude of Vd and the number of times to be adjusted may be determined after the first pre-scan.

[0175] exist Fig.10 In step S1100, it is determined whether it is necessary to read the fingerprint again according to a judgment criterion. For example, the judgment criterion may be a judgment criterion based on image quality or a judgment criterion based on the number of fingerprint readings. For example, when the number of fingerprint readings reaches a threshold (for example, the threshold is equal to or greater than 2, 3 or other values), it is determined that it is not necessary to read the fingerprint again.

[0176] In some embodiments or in the previous embodiments, the pixel voltage prediction method can be used to adjust the CDS reference voltage by finding the voltage representing the fingerprint voltage in the pre-read (pre-scan) voltage. Fig.11 As shown, the sensing voltages of the fingerprint sensing pixels can be obtained by using a representative area, where the representative area is, for example, an area (such as at CT) relative to a representative position such as the center of the representative area (such as CT). Fig.11 The representative area may be any suitable area smaller than the original fingerprint area, such as an area of ​​4x4, 6x6, 8x8 pixels, or any other area. For example, the representative position may be considered to be the center of the fingerprint image. Of course, the implementation of the present disclosure is not limited to the examples.

[0177] Then, the CDS reference level processing unit of the readout IC calculates the average value (or median value or any value representing the reference area) of the reference area to obtain a reference voltage representing the exposure voltage of the entire finger and generates a new CDS. The reference voltage is then output to the non-inverting terminal of the OP to provide the CDS reference voltage for the next "normal read" (i.e., all areas, such as the original fingerprint image area). This will help adjust the efficiency.

[0178] In some embodiments, a method for calculating (or determining) a pre-scan voltage is provided. By reducing the voltage of the fingerprint sensing pixel by pre-scanning, a representative voltage value of a representative position or a representative area (such as the center of the fingerprint) can be obtained. Fig. 12A As shown, the first sampled sampling voltage (CDS1 voltage) of the CDS generated at Vrst (or other reference voltage) is read in the readout phase 1. Fig. 12B As shown, the second sampling voltage (CDS2 voltage) of CDS is read out in the readout stage 2, and the difference Vx (Cd / Cf) is obtained by subtracting the CDS1 voltage from the CDS2 voltage, where Vx represents the voltage difference between the pixel voltages of the same fingerprint sensing pixel at the first and second sampling times. In the case where Vrst, Cd, and Cf are known parameters and Vofs is a negligible small parameter, the voltage value of Vrst+Vofs-Vx can be obtained from Vx (Cd / Cf). The method for calculating the pre-scan voltage of this embodiment is applicable to any embodiment of the required pre-scan voltage described above.

[0179] The embodiments disclosed above can improve the efficiency of acquiring (or sampling) signals by adjusting the CDS reference voltage, reducing the voltage difference between CDS samples, and reducing the time required for stabilizing the AFE output between samples.

[0180] In addition, for example, a single chip integrating a fingerprint transmission driver circuit, a touch driver circuit, and a display driver circuit can realize at least two operation cycles (or frames), a display cycle and a fingerprint cycle, which are executed (or activated) alternately to perform time-sharing operations. In some embodiments, whether the reset, sampling, and readout (abbreviated as selection or sensing) actions can be completed in one fingerprint (FPR) frame (or readout frame), or whether there is at least one display frame that enables reset and readout to be achieved in different FPR frames is determined by factors such as the operating speed of the FPR module relative to the FPR frame and the duration of the FPR frame. Therefore, the embodiments of the present invention are not limited to these examples.

[0181] In practical applications, there are different ways to achieve the above operation cycle. For example, even if the FPR module does not run fast enough, the FPR module can be designed so that the FPR frame time is sufficient so that the FPR frame can be reset, sampled and read out.

[0182] For example, in an integrated IC (such as FTDI IC, or other IC with fingerprint processing function), a display frame (or even a touch frame) can be inserted between multiple FPR frames. In addition, the display frame, FPR module and other frames can be implemented in various time-sharing ways, and the embodiments of the present invention are not limited to these examples.

[0183] Therefore, the above various embodiments of the present disclosure provide a technique for facilitating fingerprint sensing signal sampling in a computing device. The technique is used to perform dynamic reference signal adjustment in an electronic module capable of performing fingerprint sensing signal sampling. By using the technique, the electronic module capable of performing fingerprint sensing signal sampling can dynamically perform reference signal adjustment, thereby reducing the settling time of the analog front-end circuit of the electronic module.

[0184] In addition, based on the dynamic reference signal adjustment technology, the time required for sampling the fingerprint sensing signal can be shortened and can be configured within the required time interval allowed for processing the fingerprint sensing signal, thereby solving the problem of implementing the fingerprint sensing function on the full screen of the display panel.

[0185] Therefore, computing devices that perform applications such as fingerprint recognition based on the output of the electronic module can benefit from the dynamic reference signal adjustment technology, thereby improving the overall fingerprint sensing effect and efficiency of the application.

[0186] Although the present disclosure has been described with reference to specific embodiments, various modifications and changes may be made thereto by one skilled in the art without departing from the scope and spirit of the present disclosure as set forth in the claims.

Claims

1. A fingerprint sensing method, the method being applied to an electronic module capable of fingerprint sensing, characterized in that: The electronic module is used to couple to a fingerprint sensor having a plurality of fingerprint sensing pixels, the electronic module includes an analog front-end stage for coupling to the plurality of fingerprint sensing pixels, the method comprising: performing a first scanning operation on at least a first portion of the plurality of fingerprint sensing pixels by using a first reference signal applied to a reference terminal of the analog front end stage to obtain a magnitude of a second reference signal based on a sensing result of the first scanning operation; and A second scanning operation is performed on at least a second portion of the plurality of fingerprint sensing pixels by using the second reference signal applied to a reference terminal of the analog front end stage, wherein the second reference signal is different from the first reference signal.

2. The method according to claim 1, characterized in that The second part includes the first part.

3. The method according to claim 1, characterized in that The second portion corresponds to a fingerprint sensing area, and the first portion corresponds to a representative area of ​​the fingerprint sensing area.

4. The method according to claim 3, characterized in that The first scanning operation includes reading a sensing signal from at least one fingerprint sensing pixel located in a representative area of ​​the fingerprint sensing area, and the second scanning operation includes reading a sensing signal from all fingerprint sensing pixels corresponding to the fingerprint sensing area.

5. The method according to claim 1, characterized in that The method further includes performing a reset operation before the first scanning operation.

6. The method according to claim 2, characterized in that The method further comprises: Obtaining the magnitude of a third reference signal through the second scanning operation; and A third scanning operation is performed on at least a second portion of the plurality of fingerprint sensing pixels by using the third reference signal applied to a reference terminal of the analog front end stage, wherein the third reference signal is different from the second reference signal.

7. The method according to claim 1, characterized in that The first portion is equal to the second portion.

8. The method according to claim 7, characterized in that Each of the first portion and the second portion corresponds to a fingerprint sensing area.

9. The method according to claim 8, characterized in that The first scanning operation includes reading sensing signals of all fingerprint sensing pixels corresponding to the fingerprint sensing area; and the second scanning operation includes reading sensing signals of all fingerprint sensing pixels corresponding to the fingerprint sensing area.

10. The method according to claim 8, characterized in that The method further includes: performing a reset operation before the first scanning operation; and performing a reset operation before the second scanning operation.

11. The method according to claim 1, characterized in that: The method further comprises: The magnitude of the second reference signal is determined based on an average value of a plurality of fingerprint sensing values ​​resulting from the execution of the first scanning operation and the magnitude of the first reference signal.

12. The method according to claim 11, characterized in that The magnitude of the second reference signal is equal to the magnitude of the first reference signal minus an average value of the plurality of fingerprint sensing values.

13. The method according to claim 11, characterized in that The analog front end stage comprises an operational amplifier having an input terminal which serves as a reference terminal of the analog front end stage.

14. The method according to claim 13, characterized in that The second reference signal is determined so as to reduce a convergence time of the operational amplifier.

15. The method according to claim 1, characterized in that The method further comprises: determining an average of a plurality of fingerprint sensing values ​​resulting from execution of the first scanning operation; and The magnitude of the second reference signal is determined based on an average value of the plurality of fingerprint sensing values.

16. The method according to claim 15, characterized in that The magnitude of the second reference signal is equal to the magnitude of the first reference signal minus an average value of the plurality of fingerprint sensing values.

17. An electronic module capable of fingerprint sensing, characterized in that: The electronic module is used to be coupled to a fingerprint sensor having a plurality of fingerprint sensing pixels, and the electronic module comprises: Fingerprint sensing driver circuit, comprising: a fingerprint sensing circuit, which is used to couple to the fingerprint sensor and obtain fingerprint sensing data, the fingerprint sensing circuit comprising an analog front-end stage; and A control unit, coupled to the fingerprint sensing circuit and used for fingerprint sensing, wherein the control unit is configured to perform a plurality of operations, the plurality of operations comprising: performing a first scanning operation on at least a first portion of the plurality of fingerprint sensing pixels by using a first reference signal applied to a reference terminal of the analog front end stage to obtain a magnitude of a second reference signal based on a sensing result of the first scanning operation; and A second scanning operation is performed on at least a second portion of the plurality of fingerprint sensing pixels by using a second reference signal applied to a reference terminal of the analog front end stage, wherein the second reference signal is different from the first reference signal.

18. The electronic module according to claim 17, characterized in that: The second part includes the first part.

19. The electronic module according to claim 17, characterized in that: The second portion corresponds to a fingerprint sensing area, and the first portion corresponds to a representative area of ​​the fingerprint sensing area.

20. The electronic module according to claim 19, characterized in that The first scanning operation includes reading a sensing signal from at least one fingerprint sensing pixel located in a representative area of ​​the fingerprint sensing area, and the second scanning operation includes reading a sensing signal from all fingerprint sensing pixels corresponding to the fingerprint sensing area.

21. The electronic module according to claim 17, characterized in that: The plurality of operations also includes performing a reset operation prior to the first scanning operation.

22. The electronic module according to claim 18, characterized in that The plurality of operations also include: Obtaining the magnitude of a third reference signal through the second scanning operation; and A third scanning operation is performed on at least a second portion of the plurality of fingerprint sensing pixels by using the third reference signal applied to a reference terminal of the analog front end stage, wherein the third reference signal is different from the second reference signal.

23. The electronic module according to claim 17, characterized in that: The first portion is equal to the second portion.

24. The electronic module according to claim 23, characterized in that Each of the first portion and the second portion corresponds to a fingerprint sensing area.

25. The electronic module according to claim 24, characterized in that The first scanning operation includes reading sensing signals of all fingerprint sensing pixels corresponding to the fingerprint sensing area; and the second scanning operation includes reading sensing signals of all fingerprint sensing pixels corresponding to the fingerprint sensing area.

26. The electronic module according to claim 24, characterized in that The plurality of operations further include: performing a reset operation before the first scanning operation; and performing a reset operation before the second scanning operation.

27. The electronic module according to claim 17, characterized in that: The plurality of operations also include: The magnitude of the second reference signal is determined based on an average value of a plurality of fingerprint sensing values ​​resulting from the execution of the first scanning operation and the magnitude of the first reference signal.

28. The electronic module according to claim 27, characterized in that The magnitude of the second reference signal is equal to the magnitude of the first reference signal minus an average value of the plurality of fingerprint sensing values.

29. The electronic module according to claim 27, characterized in that The analog front end stage comprises an operational amplifier having an input terminal which serves as a reference terminal of the analog front end stage.

30. The electronic module according to claim 29, characterized in that The second reference signal is determined so as to reduce a convergence time of the operational amplifier.

31. The electronic module according to claim 17, characterized in that: The plurality of operations also include: determining an average of a plurality of fingerprint sensing values ​​resulting from execution of the first scanning operation; and The magnitude of the second reference signal is determined based on an average value of the plurality of fingerprint sensing values.

32. The electronic module according to claim 31, characterized in that The magnitude of the second reference signal is equal to the magnitude of the first reference signal minus an average value of the plurality of fingerprint sensing values.

33. The electronic module according to claim 17, characterized in that: The control unit is further configured to: A touch position on the touch panel is obtained, wherein the first scanning operation is performed on the first portion with respect to the touch position.

34. The electronic module according to claim 17, characterized in that The electronic module is a single chip.

35. A computing device, characterized in that: include: A touch display panel having a fingerprint sensor; as well as An electronic module capable of performing fingerprint sensing and coupled to the touch display panel, the electronic module comprising: Fingerprint sensing driver circuit, comprising: a fingerprint sensing circuit, which is used to couple to the fingerprint sensor and obtain fingerprint sensing data, the fingerprint sensing circuit comprising an analog front-end stage; and A control unit, coupled to the fingerprint sensing circuit and used for fingerprint sensing, wherein the control unit is configured to: performing a first scanning operation on at least a first portion of a plurality of fingerprint sensing pixels by using a first reference signal applied to a reference terminal of the analog front end stage to obtain a magnitude of a second reference signal based on a sensing result of the first scanning operation; and A second scanning operation is performed on at least a second portion of the plurality of fingerprint sensing pixels by using a second reference signal applied to a reference terminal of the analog front end stage, wherein the second reference signal is different from the first reference signal.

36. The computing device according to claim 35, characterized in that: The electronic module is a single chip.

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