In-screen fingerprint identification circuit

Abstract

The application discloses an in-screen fingerprint identification circuit and belongs to the technical field of in-screen fingerprint identification. The in-screen fingerprint identification circuit comprises a pixel circuit, the pixel circuit comprises a metal oxide thin film transistor, the drain electrode of the metal oxide thin film transistor is connected with a first voltage, and the gate electrode of the metal oxide thin film transistor is connected with a corresponding voltage based on the illumination condition of a pixel array; and an amplification circuit, a first input end of the amplification circuit is connected with an output end of the pixel circuit, and the amplification circuit is used for at least one of conversion, integration and filtering of the current output by the pixel circuit. The in-screen fingerprint identification circuit of the application can complete the photosensitive work of the pixel and the work of the scanning switch by using a single thin film transistor, can be compatible with a display circuit, the pixel circuit has super-high resolution, fingerprint identification in a large area can be realized, and the biological safety and user experience are significantly improved.

Description

Technical Field

[0001] The present application belongs to the field of in-screen fingerprint recognition technology, and in particular relates to an in-screen fingerprint recognition circuit. Background Art

[0002] In-screen fingerprint recognition is a modern biometric technology that allows users to unlock their devices or authenticate their identities by placing their finger or palm on the display screen. In related technologies, in-screen fingerprint recognition primarily relies on CMOS integrated circuits for optical fingerprint recognition and silicon photodiodes for photoelectric signal conversion. However, this method has relatively high equipment costs, and because it cannot be manufactured over a large area, only a specific area of ​​the screen can be used for fingerprint recognition. Users must place their finger accurately in this area, otherwise they may not be able to unlock the device, affecting the user experience. Summary of the Invention

[0003] This application aims to solve at least one of the technical problems existing in the prior art. To this end, this application proposes an in-screen fingerprint recognition circuit that uses a single thin-film transistor to complete the work of pixel photosensitivity and scanning switch, and is compatible with the display circuit, so that the pixel circuit has ultra-high resolution and fingerprint recognition over a large area, significantly improving biometric security and user experience.

[0004] In a first aspect, the present application provides an in-screen fingerprint recognition circuit, which includes:

[0005] A pixel circuit, the pixel circuit comprising a metal oxide thin film transistor, the drain of the metal oxide thin film transistor being connected to a first voltage, and the gate of the metal oxide thin film transistor being connected to a corresponding voltage based on illumination conditions of a pixel array in the pixel circuit;

[0006] An amplifier circuit, wherein a first input end of the amplifier circuit is connected to an output end of the pixel circuit, and the amplifier circuit is used to perform at least one of conversion, integration, and filtering on the current output by the pixel circuit.

[0007] According to the in-screen fingerprint recognition circuit of the present application, the pixel's photosensitivity and scanning switch operations can be completed by using a single thin-film transistor, and it can be compatible with the display circuit, so that the pixel circuit has ultra-high resolution and fingerprint recognition in a large area, with high fingerprint recognition accuracy, and occupies a small space, low design cost, and is easy to implement, significantly improving biosafety and user experience.

[0008] According to one embodiment of the present application, it further includes:

[0009] a first capacitor, one end of the first capacitor being connected to the source electrode of the metal oxide thin film transistor and the other end being grounded;

[0010] A first switch, wherein one end of the first switch is connected to the source of the metal oxide thin film transistor, and the other end of the first switch is connected to the first input end.

[0011] According to one embodiment of the present application, the source of at least one pixel circuit in the same channel is connected to one end of the same first capacitor via the same readout line.

[0012] According to an embodiment of the present application, the other ends of the first switches corresponding to multiple different channels are respectively connected to the first input end of the same amplifying circuit, and the first switches are closed in sequence based on the arrangement order of the pixel array.

[0013] According to the in-screen fingerprint recognition circuit of the present application, by adding a first capacitor and a first switch at the output end of each channel, the added first capacitor is used to first integrate the output current of each column of pixels in the readout stage, convert it into a voltage, and store it, and then output the channel signal one by one to the back end through the added first switch. Multiple channels of the pixel array can be merged, effectively reducing the complexity of the back-end circuit, saving actual costs and occupied space, and further improving the fingerprint unlocking effect.

[0014] According to one embodiment of the present application, the amplifying circuit includes:

[0015] an amplifier, wherein the first input terminal of the amplifier is connected to the output terminal of the pixel circuit, and the second input terminal of the amplifier is used to access a reference voltage;

[0016] a second capacitor, disposed between the first input terminal and the output terminal of the amplifier;

[0017] The second switch is connected in parallel with the second capacitor.

[0018] According to one embodiment of the present application, in the illumination stage, a negative voltage is applied to the gate of the metal oxide thin film transistor; in the data reading stage, a pulse voltage or a sawtooth voltage is applied to the gate of the metal oxide thin film transistor, and the metal oxide thin film transistor enters the subthreshold range.

[0019] According to one embodiment of the present application, when the metal oxide thin film transistor is a dual-gate transistor, during the light illumination phase, a high voltage is applied to the top gate of the dual-gate transistor.

[0020] According to one embodiment of the present application, in the recovery phase, a high voltage is applied to the gate of the metal oxide thin film transistor.

[0021] According to an embodiment of the present application, when the metal oxide thin film transistor is a dual-gate transistor, in the recovery phase, a low level of a first duration is applied to the top gate of the dual-gate transistor.

[0022] According to the in-screen fingerprint recognition circuit of the present application, by adopting a dual-gate transistor, compared with a single-gate thin-film transistor, the other gate of the dual-gate thin-film transistor can be used to regulate the light response, further improving the control accuracy and control effect, thereby improving the fingerprint recognition effect.

[0023] According to one embodiment of the present application, it further includes:

[0024] The driving circuit is used to provide an operating voltage for the pixel array and output a corresponding voltage to the gate of the metal oxide thin film transistor based on the illumination condition.

[0025] The above one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0026] By using a single thin-film transistor, the pixel's photosensitivity and scanning switch functions can be completed, and it is compatible with the display circuit, so that the pixel circuit has ultra-high resolution and fingerprint recognition over a large area, with high fingerprint recognition accuracy, small footprint, low design cost, and easy implementation, significantly improving biosafety and user experience.

[0027] Furthermore, by adopting a dual-gate transistor, compared with a single-gate thin-film transistor, the other gate of the dual-gate thin-film transistor can be used to regulate the light response, further improving the control accuracy and control effect, thereby improving the fingerprint recognition effect.

[0028] Furthermore, by adding a first capacitor and a first switch at the output end of each channel, the added first capacitor is used to integrate the output current of each column of pixels in the readout stage, convert it into voltage, and store it, and then output the channel signal one by one to the back end through the added first switch. In this way, multiple channels of the pixel array can be merged, effectively reducing the complexity of the back-end circuit, saving actual costs and occupied space, and further improving the fingerprint unlocking effect.

[0029] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0031] Figure 1This is one of the structural diagrams of the in-screen fingerprint recognition circuit provided in an embodiment of the present application;

[0032] Figure 2 This is a signal timing diagram of the in-screen fingerprint recognition circuit provided by an embodiment of the present application;

[0033] Figure 3 This is the second structural diagram of the in-screen fingerprint recognition circuit provided by an embodiment of the present application;

[0034] Figure 4 This is the third structural diagram of the in-screen fingerprint recognition circuit provided by the embodiment of the present application;

[0035] Figure 5 This is the fourth structural diagram of the in-screen fingerprint recognition circuit provided by an embodiment of the present application;

[0036] Figure 6 This is a schematic diagram of the principle of the in-screen fingerprint recognition circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0038] It should be noted that the terms "first," "second," etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than those illustrated or described herein, and that the objects distinguished by "first," "second," etc. are generally of the same type, and do not limit the number of objects. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0039] The terms "upper", "lower", "front", "back", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the present application and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as limiting the present application. The terms "installed", "connected", and "connected" should be understood in a broad sense. For example, they can be fixed connections, detachable connections, or integral connections; they can be mechanical connections or electrical connections; they can be direct connections or indirect connections through an intermediate medium, and they can be internal connections between two components. The terms "parallel", "perpendicular", and "equal" include the situations described and situations similar to the situations described, and the range of the similar situations is within an acceptable deviation range, where the acceptable deviation range is determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes both absolute parallelism and approximate parallelism, where the acceptable deviation range for approximate parallelism may be, for example, within 5°; "perpendicular" includes both absolute perpendicularity and approximate perpendicularity, where the acceptable deviation range for approximate perpendicularity may also be, for example, within 5°. "Equal" includes both absolute equality and approximate equality, where the acceptable deviation range for approximate equality may be, for example, that the difference between the two is less than or equal to 5% of either. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0040] like Figure 1 As shown, the in-screen fingerprint recognition circuit includes: a pixel circuit and an amplification circuit.

[0041] The pixel circuit is used for optical signal recognition and is a photoelectric sensing pixel circuit used to complete optical in-screen fingerprint recognition.

[0042] The pixel circuit includes a metal oxide thin-film transistor (MOTFT), which is a field effect transistor (FET) with a metal oxide semiconductor material as the active layer.

[0043] In some embodiments, the metal oxide thin-film transistor may also be a full metal oxide thin-film transistor (FMOTFT). A full metal oxide thin-film transistor (FMOTFT) is a thin-film transistor (TFT) whose channel layer, gate insulating layer, and electrodes are all made of metal oxide materials. Compared to traditional amorphous silicon (a-Si) or polycrystalline silicon (LTPS) TFTs, FMOTFTs, due to the excellent properties of metal oxides, have shown great potential in high-resolution displays, flexible electronics, and transparent electronic devices.

[0044] like Figure 1 As shown, the drain of the metal oxide thin film transistor is connected to the first voltage VDD, the gate of the metal oxide thin film transistor is connected to the corresponding voltage based on the illumination condition of the pixel array, and the source of the metal oxide thin film transistor can be used as the output end of the pixel circuit and connected to the first input end of the amplifier circuit.

[0045] The amplifier circuit is used to perform at least one of conversion, integration, and filtering on the current output by the pixel circuit. The amplifier circuit can be an integrator circuit, a charge amplifier, or a transimpedance amplifier.

[0046] The amplifier circuit includes a first input terminal, a second input terminal and an output terminal. The first input terminal of the amplifier circuit is connected to the output terminal of the pixel circuit. The second input terminal of the amplifier circuit is used to access the reference voltage V REF , to provide a stable voltage reference. The output end of the amplifier circuit is used to output an electrical signal. The output electrical signal can characterize the light conditions acting on the pixel circuit, and then generate fingerprint features based on the electrical signal, thereby realizing in-screen fingerprint recognition.

[0047] It can be understood that in the process of in-screen fingerprint recognition, optical fingerprint recognition is achieved based on the optical reflection difference of the fingerprint pattern, that is, the raised part of the ridge fingerprint can directly contact the sensor surface and the reflected light is stronger; while there is an air gap between the concave part of the valley fingerprint and the sensor, and the reflected light is weaker; the sensor captures the brightness difference of the reflected light to generate a fingerprint image.

[0048] During the research and development process, the inventors discovered that under the irradiation of light, the threshold voltage of the metal oxide thin film transistor will shift, and the degree of shift increases with the increase of illumination time and the increase of light intensity; the shift of the threshold voltage is reversible, and the process can occur within milliseconds. By extracting the degree of threshold voltage shift, it can be used to characterize the optical signal, thereby realizing fingerprint recognition.

[0049] Figure 6The transfer curve of a double-gate metal oxide thin film transistor with a width-length ratio of 10um / 10um under irradiation of different light powers for 100ms and the transfer curve after irradiation is shown. Figure 6 It can be seen that, compared with the transfer curve in the dark state, the threshold voltage of the metal oxide thin film transistor under irradiation of light will be negatively biased, the degree of offset is proportional to the light power, and the leakage current does not increase during irradiation. Finally, the transfer curve after irradiation returns to the same as in the dark state. This threshold voltage offset is long-term and reversible, that is, the irradiation information can be measured by the amount of threshold voltage offset. By using the threshold voltage offset as a measure of light response, a single metal oxide thin film transistor can be used as a photoelectric sensor and as a column selection switch when the pixel array is output. The bottom gate is used as the column selection signal, that is, Figure 5 the scanning signal Scan in

[0050] In the present application, by setting a pixel circuit including a metal oxide thin film transistor, when a finger approaches the screen, different positions will emit different light. The metal oxide thin film transistor will capture the reflected light and generate a current signal matching the light intensity according to the voltage offset of the reflected light. The current signal is processed by an amplification circuit to convert it into a voltage signal. The voltage signal changes with the change of the light intensity of the reflected light acting on the pixel circuit, which can accurately reflect the change of the light intensity, so that the corresponding fingerprint features can be generated based on the size difference of the voltage signal to generate a fingerprint image, realizing in-screen fingerprint recognition. It has high accuracy, and only one metal oxide thin film transistor is needed for one pixel circuit, which occupies small space and has low design cost, and is easy to implement.

[0051] In actual implementation, the light source for illuminating the fingerprint area required for fingerprint recognition can be an LED or a self-emitting screen pixel.

[0052] As shown in Figure 4 , in some embodiments, the in-screen fingerprint recognition circuit can further include a driving circuit.

[0053] In this embodiment, the driving circuit is used to provide working voltage for the pixel array and output corresponding voltage to the gate of the metal oxide thin film transistor based on the light condition.

[0054] In some embodiments, the metal oxide thin film transistor can include a single-gate transistor or a double-gate transistor.

[0055] In this embodiment, the single-gate transistor (Single-Gate MOTFT) has only one gate, which is usually located above or below the channel. The channel carriers are controlled by a single electric field. The gate voltage VG forms a vertical electric field below the insulating layer, modulating the channel carrier concentration (electrons or holes), thereby controlling the source-drain current IDS.

[0056] A double-gate transistor (Double-Gate MOTFT) consists of two gates, a top gate and a bottom gate, which apply electric fields from the upper and lower sides of the channel to enhance control over the channel. The top gate and bottom gate can be biased independently or synchronously to form a stronger vertical electric field and more efficiently control the channel carriers.

[0057] According to the in-screen fingerprint recognition circuit provided in the embodiment of the present application, by providing multiple configuration modes such as single-gate transistors or double-gate transistors, flexible selection can be made based on actual conditions.

[0058] During the research and development process, the inventors also discovered that in the related technology, in-screen fingerprint recognition mainly relies on CMOS integrated circuits for optical fingerprint recognition. This method is similar to CMOS image sensors and mainly relies on silicon photodiodes for photoelectric signal conversion, resulting in relatively high costs for such in-screen fingerprint recognition devices; and because it cannot be prepared over a large area, only specific areas of the screen can be used for fingerprint recognition. Users must place their fingers accurately in this area, otherwise they may not be able to unlock the device, thus affecting the user experience; in addition, at least two devices are required in the pixel circuit of the traditional fingerprint recognition circuit to complete the photoelectric conversion, which takes up a large amount of space.

[0059] The in-screen fingerprint recognition circuit provided by the present application includes a pixel array. By setting a single metal oxide thin film transistor in each pixel circuit in the pixel array for light signal recognition and conversion, when the light signal enters the pixel array, the threshold voltage of the metal oxide thin film transistor in some pixel circuits is offset. Through the pixel circuit and the amplification circuit, the offset of the threshold voltage of the metal oxide thin film transistor can be extracted, and a fingerprint image is generated based on the offset, thereby realizing fingerprint recognition; finally, the threshold voltage of the metal oxide thin film transistor with the threshold voltage offset is restored to reset the circuit and wait for the next fingerprint recognition, with a more accurate fingerprint recognition effect and a higher response rate.

[0060] In addition, only a single thin-film transistor is required in the pixel circuit of the present application to complete the pixel's photosensitivity and scanning switch work, which occupies a small space and has a low design cost. The manufacturing process of the metal oxide thin-film transistor is easy, and large-area preparation is not difficult. It can support large-area preparation, and the photoelectric sensing pixel can be integrated with the current screen display pixel circuit. The fingerprint recognition area can be expanded to the entire panel at a lower cost, so that fingerprint recognition can be performed without being in a specific area of ​​the screen, and in-screen fingerprint recognition can be achieved in a larger range at a lower cost, thereby improving the user experience.

[0061] According to the in-screen fingerprint recognition circuit provided in the embodiment of the present application, the pixel's photosensitivity and scanning switch operations can be completed by using a single thin-film transistor, and it can be compatible with the display circuit, so that the pixel circuit has ultra-high resolution and fingerprint recognition in a large area, with high fingerprint recognition accuracy, and occupies a small space, has a low design cost, is easy to implement, and significantly improves biosafety and user experience.

[0062] Continue to refer Figure 1 In some embodiments, the amplifying circuit may include: an amplifier AMP, a second capacitor C F and the second switch S RST .

[0063] In this embodiment, the first input terminal of the amplifier AMP is connected to the output terminal of the pixel circuit, and the second input terminal is used to access the reference voltage V REF ; The second capacitor C F The second switch S is provided between the first input terminal and the output terminal of the amplifier AMP; RST With the second capacitor C F Parallel setting.

[0064] The second switch S RST The opening and closing state of the second switch S is controlled by the first signal. The first signal is a switch signal. When the first signal is high, the second switch S RST Closed; when the first signal is low, the second switch S RST disconnect.

[0065] The specific execution logic of the in-screen fingerprint recognition circuit is explained below.

[0066] During the fingerprint recognition process, there are an illumination stage, a data reading stage, and a recovery stage arranged in sequence. The illumination stage is a stage with strong reflected light; the data reading stage is a stage with weak reflected light, which is used to read data; the recovery stage is the stage where fingerprint recognition ends and the threshold voltage of the metal oxide thin film transistor that has undergone threshold voltage shift needs to be restored.

[0067] In some embodiments, during the light illumination phase, a negative voltage may be applied to the gate of the metal oxide thin film transistor. In some embodiments, the negative voltage may range from -20V to 0V.

[0068] In some embodiments, during the data reading phase, a pulse voltage or a sawtooth voltage may be applied to the gate of the metal oxide thin film transistor to cause the metal oxide thin film transistor to enter a subthreshold region.

[0069] Among them, the subthreshold range is the working area corresponding to the subthreshold current where the gate voltage of the metal oxide thin film transistor is lower than the threshold voltage and the channel is not fully formed but there is still a weak current.

[0070] In some embodiments, a sawtooth voltage may be selected to accommodate device non-uniformities.

[0071] In some embodiments, during the recovery phase, a high voltage may be applied to the gate of the metal oxide thin film transistor. In some embodiments, the high voltage may range from 5V to 10V to restore it to its initial threshold voltage. The high voltage is greater than the pulse voltage or the sawtooth voltage.

[0072] The gate voltage applied to the gate of the metal oxide thin film transistor changes as shown in the figure. Figure 2 As shown, Light represents the change in light intensity. The high level is used to represent the light stage, and the low level is used to represent the data reading stage and the subsequent response stage. The corresponding gate voltage changes in different stages are shown in V BG1 shown.

[0073] According to the in-screen fingerprint recognition circuit provided in the embodiment of the present application, by acting on different lighting conditions of the metal oxide thin film transistor and applying corresponding voltage to the gate of the metal oxide thin film transistor, the optical signal can be converted into an electrical signal through only a single thin film transistor, thereby realizing the generation and recognition of fingerprint images, having high fingerprint recognition accuracy, taking up little space, low design cost, and being easy to implement.

[0074] In some embodiments, when the metal oxide thin film transistor is a dual-gate transistor, a high voltage may be applied to the top gate of the dual-gate transistor during the light illumination phase.

[0075] In some embodiments, when the metal oxide thin film transistor is a dual-gate transistor, in the recovery phase, a low level of a first duration is applied to the top gate of the dual-gate transistor.

[0076] In this embodiment, the first duration may be based on user customization.

[0077] The bottom gate voltage applied to the bottom gate of the metal oxide thin film transistor changes as described in the above embodiment, that is, in the illumination stage, a negative voltage is applied to the bottom gate; in the data reading stage, a pulse voltage or a sawtooth voltage is applied to the bottom gate; in the recovery stage, a high voltage is applied to the bottom gate.

[0078] The top gate voltage applied to the top gate of the metal oxide thin film transistor changes as shown in the figure. Figure 2 Medium V TG shown.

[0079] The following takes a metal oxide thin film transistor as a dual-gate transistor as an example to illustrate its implementation logic.

[0080] The photosensitive signal of the metal oxide thin film transistor is characterized by the light response in the form of threshold voltage shift, and its working timing is as follows: Figure 2 As shown, in the illumination stage, the light source is turned on, the top gate voltage is pulled high, all bottom gate voltages are negative voltages, the metal oxide thin film transistor is in the off state, and the illumination causes the threshold voltage of the metal oxide thin film transistor to shift.

[0081] After the illumination ends, the light source is stopped and the data reading phase begins. At this time, a pulse voltage is applied to the bottom gate. Considering the heterogeneity of the device, the pulse voltage can be replaced with a sawtooth voltage to put the metal oxide thin film transistor in the subthreshold range and generate a subthreshold current. The subthreshold current flows into the first input terminal of the amplifier circuit and is converted from current to voltage by the current integrator of the amplifier circuit to output a voltage signal V OUT The voltage signal can represent the light intensity acting on the pixel circuit, which is convenient for generating the corresponding fingerprint feature.

[0082] Finally, a recovery phase is entered to restore the metal oxide thin film transistor to its initial state, and a high voltage is applied to the bottom gate for recovery.

[0083] In some embodiments, a low level of a first duration may be applied to the top gate to improve the stability of the metal oxide thin film transistor.

[0084] According to the in-screen fingerprint recognition circuit provided in the embodiment of the present application, by adopting a dual-gate transistor, compared with a single-gate thin-film transistor, the other gate of the dual-gate thin-film transistor can be used to regulate the light response, further improving the control accuracy and control effect, thereby improving the fingerprint unlocking effect.

[0085] like Figure 3 As shown, in some embodiments, the in-screen fingerprint recognition circuit may further include: a first capacitor C1 and a first switch S1.

[0086] In this embodiment, one end of the first capacitor C1 is connected to the source of the metal oxide thin film transistor, and the other end is grounded; one end of the first switch S1 is connected to the source of the metal oxide thin film transistor, and the other end is connected to the first input terminal.

[0087] The first capacitor C1 is used to integrate the output current of each column of pixels in the readout phase, convert it into a voltage, and store it.

[0088] The first switch S1 is used to control the connection and disconnection between the first capacitor C1 and the amplifier circuit. When the first switch S1 is closed, the electrical signal stored in the first capacitor C1 will be output to the amplifier circuit.

[0089] like Figure 5 As shown, the source of at least one pixel circuit in the same channel is connected to one end of the same first capacitor C1 via the same readout line.

[0090] Continue to refer Figure 3 The other ends of the first switches S1 corresponding to the multiple different channels are respectively connected to the first input end of the same amplifier circuit, and the first switches S1 are closed in sequence based on the arrangement order of the pixel array.

[0091] Figure 5 This diagram illustrates the structure of an in-screen fingerprint recognition circuit, including a pixel array comprising multiple pixel circuits. All metal oxide thin film transistors (MTs) in each pixel circuit are connected to the same power supply to access a first voltage, VDD. The sources of the TFTs in the same channel are connected to the same readout line and the same first capacitor, C1. The gates (or bottom gates) of the MTs in the same column are connected to a scan signal, Scan. The top gates of the MTs are connected to the same bias signal, namely, a top gate voltage, V TG ;The output line is connected to the amplifier circuit through the control selector and output.

[0092] In the actual implementation process, Figure 4As shown, the driver circuit provides the appropriate operating voltage for the pixel array and outputs signal timing through the control system. During the illumination phase, it outputs an appropriate gate voltage to position the metal oxide thin film transistors in the light-sensitive region. During the data readout phase, it provides the pixel array with a column scan signal, such as a sawtooth or square wave waveform, to position the metal oxide thin film transistors in the subthreshold region, generating a subthreshold current. Under the control of the control system, after illumination, the pixel array, driven by the column scan signal from the driver circuit, sequentially outputs the subthreshold current column by column to the first capacitor C1 of the channel for current integration. After current integration is completed, the first switch S1 on each channel opens sequentially, outputting the integrated value for each channel to the amplifier circuit of the readout circuit for signal current-to-voltage conversion and filtering. The signal is then input into the acquisition circuit of the readout circuit and finally transmitted back to the control system for data processing, generating a fingerprint image for fingerprint recognition. Finally, the driver circuit applies a positive voltage pulse to the top and bottom gates to reset the entire pixel array.

[0093] The acquisition circuit may include an ADC or a comparator, etc.

[0094] According to the in-screen fingerprint recognition circuit of the embodiment of the present application, by adding a first capacitor C1 and a first switch S1 to the output end of each channel, the added first capacitor C1 is used to first integrate the output current of each column of pixels in the readout stage, convert it into a voltage, and store it, and then output the channel signal one by one to the back end through the added first switch S1. In this way, multiple channels of the pixel array can be merged, effectively reducing the complexity of the back-end circuit, saving actual costs and occupied space, and further improving the fingerprint unlocking effect.

[0095] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

[0096] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0097] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and intent of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. An in-screen fingerprint recognition circuit, characterized in that: include: A pixel circuit, the pixel circuit comprising a metal oxide thin film transistor, wherein a drain of the metal oxide thin film transistor is connected to a first voltage, and a gate of the metal oxide thin film transistor is connected to a corresponding voltage based on illumination conditions of the pixel array; an amplifier circuit, wherein a first input terminal of the amplifier circuit is connected to an output terminal of the pixel circuit, and the amplifier circuit is configured to perform at least one of conversion, integration, and filtering on a current output by the pixel circuit; a first capacitor, one end of the first capacitor being connected to the source electrode of the metal oxide thin film transistor and the other end being grounded; a first switch, wherein one end of the first switch is connected to the source of the metal oxide thin film transistor, and the other end of the first switch is connected to the first input end; The in-screen fingerprint recognition circuit can complete the work of pixel photosensitivity and scanning switch by using a single thin film transistor.

2. The in-screen fingerprint recognition circuit according to claim 1, characterized in that: The source of at least one pixel circuit in the same channel is connected to one end of the same first capacitor via the same readout line.

3. The in-screen fingerprint recognition circuit according to claim 2, characterized in that: The other ends of the first switches corresponding to a plurality of different channels are respectively connected to the first input end of the same amplifying circuit, and the first switches are closed in sequence based on the arrangement order of the pixel array.

4. The in-screen fingerprint recognition circuit according to any one of claims 1 to 3, characterized in that: The amplifying circuit comprises: an amplifier, wherein the first input terminal of the amplifier is connected to the output terminal of the pixel circuit, and the second input terminal of the amplifier is used to access a reference voltage; a second capacitor, disposed between the first input terminal and the output terminal of the amplifier; The second switch is connected in parallel with the second capacitor.

5. The in-screen fingerprint recognition circuit according to any one of claims 1 to 3, characterized in that: In the illumination stage, a negative voltage is applied to the gate of the metal oxide thin film transistor; in the data reading stage, a pulse voltage or a sawtooth voltage is applied to the gate of the metal oxide thin film transistor, and the metal oxide thin film transistor enters the subthreshold range.

6. The in-screen fingerprint recognition circuit according to claim 5, characterized in that: When the metal oxide thin film transistor is a dual-gate transistor, a high voltage is applied to the top gate of the dual-gate transistor during the light illumination phase.

7. The in-screen fingerprint recognition circuit according to any one of claims 1 to 3, characterized in that: In the recovery phase, a high voltage is applied to the gate of the metal oxide thin film transistor.

8. The in-screen fingerprint recognition circuit according to claim 7, characterized in that: In the case where the metal oxide thin film transistor is a dual-gate transistor, in the recovery phase, a low level of a first duration is applied to the top gate of the dual-gate transistor.

9. The in-screen fingerprint recognition circuit according to any one of claims 1 to 3, characterized in that: Also includes: The driving circuit is used to provide an operating voltage for the pixel array and output a corresponding voltage to the gate of the metal oxide thin film transistor based on the illumination condition.

Images