CN111814632A - Capacitive screen and electronic equipment - Google Patents
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- CN111814632A CN111814632A CN202010608883.XA CN202010608883A CN111814632A CN 111814632 A CN111814632 A CN 111814632A CN 202010608883 A CN202010608883 A CN 202010608883A CN 111814632 A CN111814632 A CN 111814632A
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- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
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Abstract
The application discloses capacitive screen and electronic equipment belongs to the fingerprint identification field. Wherein, the electric capacity screen comprises a plurality of pixel, and the pixel includes: the mutual capacitor comprises a first electrode and a second electrode which are oppositely arranged, the second electrode is a fingerprint contact electrode of the capacitive screen, and the first electrode is connected with a power supply end of the capacitive screen; the reset switch is connected between the power supply end of the capacitive screen and the second electrode; the input end of the source follower is connected with the second electrode, the output end of the source follower is the fingerprint signal output end of the pixel point, and the power supply end of the source follower is connected with the power supply end of the capacitive screen; the first switch control signal output end of the first control unit is connected with the control end of the source follower; and a second switch control signal output end of the second control unit is connected with the control end of the reset switch. The problem of to passive form fingerprint identification scheme, the SNR is low and fingerprint ridge is low with fingerprint valley contrast is solved.
Description
Technical Field
The application belongs to the technical field of fingerprint identification, and particularly relates to a capacitive screen and electronic equipment.
Background
The capacitive fingerprint identification technology is widely applied to the fields of intelligent terminals, door lock security, identity records and the like due to the advantages of good stability, simple process and low cost.
At present, the principle of capacitive fingerprint identification is shown in fig. 1, when a user presses a finger onto a surface of a fingerprint identification device, because a human fingerprint is in a rugged shape, a fingerprint ridge is in close contact with the surface of the fingerprint identification device without leaving a gap, and a fingerprint valley is not in close contact with the surface of the fingerprint identification device and has an air gap. Thus, the difference in capacitance between the transmitting end (Transmit; Tx) and the receiving end (Receive; Rx) at various positions in the fingerprint identification device is caused by the difference in the contact condition between the fingerprint valley and the fingerprint ridge and the surface of the fingerprint identification device. The fingerprint identification equipment can obtain a fingerprint image by processing different capacitance signals at each position. The surface of the fingerprint identification device is a cover plate or a coating, Tx and Rx are arranged in an insulating layer adjacent to the cover plate or the coating, and a sensor substrate is arranged on the other surface of the insulating layer.
Based on the capacitive fingerprint identification principle, a passive capacitive fingerprint identification scheme is proposed at present. However, for passive fingerprint identification schemes, there is a low signal-to-noise ratio and a corresponding capacitance signal C at the fingerprint ridgeRidgeCapacitance signal C corresponding to fingerprint valleyGrainThe problem of small phase difference, i.e. low contrast between fingerprint ridges and fingerprint valleys, results in a limited use scenario for passive fingerprint identification schemes.
Disclosure of Invention
The embodiment of the application aims to provide a capacitive screen, which can solve the problems of low signal to noise ratio and low contrast between fingerprint ridges and fingerprint valleys of a passive fingerprint identification scheme.
In order to solve the technical problem, the present application is implemented as follows:
in a first aspect, an embodiment of the present application provides a capacitive screen, where the capacitive screen is composed of a plurality of pixel points, and each pixel point includes:
the mutual capacitor comprises a first electrode and a second electrode which are oppositely arranged, wherein the second electrode is a fingerprint contact electrode of the capacitive screen, and the first electrode is connected with a power supply end of the capacitive screen;
the reset switch is connected between the power supply end of the capacitive screen and the second electrode;
the input end of the source follower is connected with the second electrode, the output end of the source follower is the fingerprint signal output end of the pixel point, and the power supply end of the source follower is connected with the power supply end of the capacitive screen;
a first switch control signal output end of the first control unit is connected with a control end of the source follower;
and a second switch control signal output end of the second control unit is connected with the control end of the reset switch.
In a second aspect, an embodiment of the present application provides an electronic device, which includes the capacitive screen according to the first aspect.
In an embodiment of the present application, a capacitive screen is provided. This electric capacity screen comprises a plurality of pixel, and the pixel includes: mutual capacitance, reset switch, source follower, first control unit and second control unit. The output end of the second switch control signal of the second control unit is connected with the control end of the reset switch, so that the second switch control signal output by the second control unit is input into the reset switch through the control end of the reset switch, and the reset switch can carry out periodic reset on the source follower. When the finger of the user touches the capacitive screen, the mutual capacitance can sense the touch of the fingerprint of the finger of the user on the second electrode, so that the voltage change of the mutual capacitance is realized. The output end of the first switch control signal of the first control unit is connected with the control end of the source follower, so that after the reset switch resets the source follower, the first switch control signal output by the first control unit is input into the source follower through the control end of the source follower, and the source follower outputs a sensing signal obtained by performing voltage sensing and amplifying on the mutual capacitor, namely a fingerprint signal. Because the pixel in the capacitive screen that this application embodiment provided, accessible source follower carries out voltage induction to mutual capacitance to fingerprint signal to sensing enlargies and output, like this, can obtain the fingerprint signal of the fingerprint touch capacitive screen corresponding to user's finger of big amplitude, and is further, makes the SNR of pixel improve to and the difference increase of fingerprint signal of the fingerprint ridge that corresponds the pixel with the fingerprint valley, improved the contrast of fingerprint ridge and fingerprint valley promptly. Therefore, the capacitive screen provided by the embodiment of the application can be applied to wider fingerprint identification scenes.
Drawings
FIG. 1 is a schematic diagram of the principle of capacitive fingerprint recognition;
fig. 2 is a schematic structural diagram of a capacitive screen according to an embodiment of the present application;
FIG. 3 is a timing diagram of a level signal according to an embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of a source follower and a reset switch provided in an embodiment of the present application;
fig. 5 is a schematic structural diagram of another source follower and reset switch provided in the embodiment of the present application;
fig. 6 is a schematic structural diagram of a capacitive screen according to an embodiment of the present application;
fig. 7 is a schematic view of a process structure of a pixel provided in an embodiment of the present application;
fig. 8 is a schematic diagram of a pixel point model for sensing a fingerprint valley in a capacitive screen according to an embodiment of the present disclosure;
fig. 9 is a schematic diagram of a pixel point model for sensing fingerprint ridges in a capacitive screen according to an embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The terms first, second and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application are capable of operation in sequences other than those illustrated or described herein. In addition, "and/or" in the specification and claims means at least one of connected objects, a character "/" generally means that a preceding and succeeding related objects are in an "or" relationship.
The capacitive screen and the electronic device provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings through specific embodiments and application scenarios thereof.
The embodiment of the present application provides a capacitive screen, as shown in fig. 2, the capacitive screen is composed of a plurality of pixel points, and in the embodiment of the present application, the number of the pixel points included in the capacitive screen is not limited.
For a pixel point in a capacitive screen, the method comprises the following steps: mutual capacitance 10, reset switch 20, source follower 30, first control unit 40, and second control unit 50.
The mutual capacitor 10 comprises a first electrode 101 and a second electrode 102 which are oppositely arranged, wherein the second electrode 102 is a fingerprint contact electrode of the capacitive screen, and the first electrode 101 is connected to the power supply terminal 60 of the capacitive screen;
a reset switch 20, the reset switch 20 being connected 102 between the power terminal 60 and the second electrode of the capacitive screen;
the input end of the source follower 30 is connected with the second electrode 102, the output end of the source follower 30 is a fingerprint signal output end of a pixel point, and the power supply end of the source follower 30 is connected with the power supply end 60 of the capacitive screen;
a first control unit 40, wherein a first switch control signal output end of the first control unit 40 is connected with a control end of the source follower 30;
and a second control unit 50, wherein a second switch control signal output end of the second control unit 50 is connected with the control end of the reset switch 20.
In the embodiment of the present application, the first electrode 101 of the mutual capacitor 10 serves as the transmitting terminal Tx shown in fig. 1, and the second electrode 102 serves as the receiving terminal Rx shown in fig. 1. The mutual capacitance is used for sensing the touch of the user finger to the second electrode 102, thereby realizing the voltage change of the mutual capacitance 10.
It will be appreciated that the touch of the user's finger to the second electrode 102 is essentially a touch of the fingerprint of the user's finger to the second electrode 102. And, in the case where the second electrode 102 is not touched by the user's finger, the voltage of the mutual capacitance 10 will not change.
The second control unit 50 outputs a second switch control signal, which is a periodic level signal Vreset, through the second switch control signal output terminal. The level signal Vreset is input to the reset switch 20 through the control terminal of the reset switch 20, so that the reset switch 20 is controlled to periodically reset the source follower 30.
The first control unit 40 outputs the first switch control signal through the first switch control signal output terminal, which is a periodic level signal Vgate. After the reset switch 20 resets the source follower 30, the level signal Vgate is input to the source follower 30 through the control terminal of the source follower 30, so that the source follower 30 outputs an induced signal obtained by voltage-inducing and amplifying the mutual capacitor 10, that is, a fingerprint signal.
In the embodiment of the present application, the level signal Vreset and the level signal Vgate have an association relationship, as shown in fig. 3, specifically: at time t1, level signal Vreset is at a high level and Vgate is at a low level; at time t2, level signal Vreset is at a low level and Vgate is at a low level; at time t3, Vreset is at a low level and Vgate is at a high level. The above-mentioned time t1 to time t3 are repeated.
With reference to fig. 3, the work flow of one pixel point is as follows: at time t1, the level signal Vreset is at a high level and Vgate is at a low level, at which time the source follower 30 is reset. At time t2, when Vreset is at a low level and Vgate is at a low level, and when the user touches the second electrode with a finger, the voltage of the mutual capacitance 10 changes, and the source follower 30 senses the voltage of the mutual capacitance 10 and amplifies the sensing Signal. At time t3, Vreset is at low level and Vgate is at high level, and source follower 30 outputs the amplified sense Signal. Based on this, the time t1 can be understood as the reset time, the time t2 can be understood as the sampling time, and the time t3 can be understood as the output time.
In one embodiment of the present application, a separate first control unit 40 and a separate second control unit 50 may be included for each pixel in the capacitive screen. In this embodiment, for the pixels in the same scanning row or column, the second switch control signal output by the second control unit 50 is the same periodic level signal Vreset, so that the pixels in the same scanning row or scanning column are reset at the same time, and row or column reset of the capacitive screen can be realized.
Or, for each pixel point in the capacitive screen, the second switch control signal output by the second control unit 50 is the same periodic level signal Vreset, so that all the pixel points in the capacitive screen are reset at the same time, and the frame reset of the capacitive screen can be realized.
And, for the pixels in the same scanning line or column, the first switch control Signal output by the first control unit 40 is the same periodic level Signal Vgate, so that the corresponding source followers 30 of the pixels in the same scanning line or column can simultaneously output the sensing Signal.
It should be noted that, as shown in fig. 3, in a case that the capacitive screen implements row or column reset, after the pixel point of the previous scanning row or column outputs a high level in the first switch control signal of the first control unit 40, the first switch control signal of the first control unit 40 of the pixel point of the current scanning row or column outputs a high level. Based on this, it can be realized that the corresponding source follower 30 outputs the sensing Signal simultaneously in the row-by-row or column-by-column pixel points. Here, Vgate1 indicates that the pixel point of the first scan line or column corresponds to the first switch control signal Vgate output by the first control unit 40. Vgate N indicates the first switch control signal Vgate output by the first control unit 40 corresponding to the pixel point of the nth scanning row or column.
Based on the description of the first control unit 40 and the second control unit 50 in the above embodiment, in an embodiment of the present application, for pixel points in the same scan line or column in the capacitive screen, the same first control unit 40 and the same second control unit 50 may be shared, so that the wiring load of the capacitive screen may be reduced, and the signal-to-noise ratio of the pixel points may be improved.
Based on the description of the first control unit 40 and the second control unit 50 in the above embodiments, in another embodiment of the present application, the same second control unit 50 may be shared for each pixel point in the capacitive screen. That is, the control terminals of the reset switches 20 of different pixel points in the capacitive screen are connected to the output terminal of the second switch control signal of the same second control unit 50. And, the same first control unit 40 can be shared by the pixels in the same scanning line or column. Therefore, the wiring load of the capacitive screen can be reduced in a sharing mode, and the signal to noise ratio of the pixel points is improved.
In addition, based on the first control unit 40 and the second control unit 50, it can be understood that the capacitive screen provided in the embodiment of the present application is a capacitive screen for active fingerprint identification.
In an embodiment of the present application, a capacitive screen is provided. This electric capacity screen comprises a plurality of pixel, and the pixel includes: mutual capacitance, reset switch, source follower, first control unit and second control unit. The output end of the second switch control signal of the second control unit is connected with the control end of the reset switch, so that the second switch control signal output by the second control unit is input into the reset switch through the control end of the reset switch, and the reset switch can carry out periodic reset on the source follower. When the finger of the user touches the capacitive screen, the mutual capacitance can sense the touch of the fingerprint of the finger of the user on the second electrode, so that the voltage change of the mutual capacitance is realized. The output end of the first switch control signal of the first control unit is connected with the control end of the source follower, so that after the reset switch resets the source follower, the first switch control signal output by the first control unit is input into the source follower through the control end of the source follower, and the source follower outputs a sensing signal obtained by performing voltage sensing and amplifying on the mutual capacitor, namely a fingerprint signal. Because the pixel in the capacitive screen that this application embodiment provided, accessible source follower carries out voltage sensing to mutual capacitance to amplify and export the signal of sensing, like this, can obtain the fingerprint signal of the fingerprint touch capacitive screen corresponding to user's finger of large amplitude, further, make the SNR of pixel improve, and the difference increase of fingerprint signal of the fingerprint ridge that and fingerprint valley correspond the pixel, improved the contrast of fingerprint ridge and fingerprint valley promptly. Therefore, the capacitive screen provided by the embodiment of the application can be applied to wider fingerprint identification scenes. Among these, the broader fingerprinting scenarios include: a fingerprint identification scene with larger interval between a first electrode and a second electrode of mutual capacitance; and a fingerprint identification scenario for a larger area capacitive screen.
In one embodiment, as shown in fig. 4, the source follower 30 includes a first thin film transistor 301 and a second thin film transistor 302, and the reset switch 20 is a third thin film transistor 201.
The drain of the first thin film transistor 301 serves as the output terminal of the source follower, the gate of the first thin film transistor 301 serves as the control terminal of the source follower 30, and the source of the first thin film transistor 301 is connected to the drain of the second thin film transistor 302.
The gate of the second thin film transistor 302 serves as the input terminal of the source follower 30, and the source of the second thin film transistor 302 serves as the power supply terminal of the source follower 30.
The gate of the third thin film transistor 201 is used as the control terminal of the reset switch, the drain of the third thin film transistor 201 is connected to the second electrode 102, and the source of the third thin film transistor 201 is connected to the power terminal 60 of the capacitive screen.
In the embodiment of the present application, since the source and the drain of the thin film transistor are completely symmetrical, the source and the drain of the first thin film transistor 301, the second thin film transistor 302, and the third thin film transistor 201 described above are interchangeable.
Note that the dotted line in fig. 4 indicates the position touched by the user's finger.
In the present embodiment, the reset switch 20 and the source follower 30 may be implemented by 3 Thin Film Transistors (TFTs). Therefore, the structural complexity of the pixel points can be reduced.
As shown in fig. 4, when the capacitive screen is reset for a scan line or a scan column, the second control unit 40 included in the pixel point in the same scan line or scan column may be the first control unit 50 in the pixel point in the previous scan line or scan column. In this embodiment, the wiring load of the capacitive screen can be reduced in a shared manner, so that the signal-to-noise ratio of the pixel point is improved.
In one embodiment of the present application, as shown in fig. 5, the source follower 30 includes: a fourth thin film transistor 303, a fifth thin film transistor 304, and the reset switch 20 is a PMOS transistor 202.
The source of the PMOS transistor 202 is connected to the power terminal 60 of the capacitive screen, the gate of the PMOS transistor 202 serves as the control terminal of the reset switch, and the drain of the PMOS transistor 202 is connected to the second electrode 102.
The gate of the fourth thin film transistor 303 serves as the control terminal of the source follower 30, the drain of the fourth thin film transistor 303 serves as the control output terminal of the source follower 30, and the source of the fourth thin film transistor 303 is connected to the drain of the fifth thin film transistor 304.
The gate of the fifth thin film transistor 304 serves as the input terminal of the source follower 30, and the source of the fifth thin film transistor 304 is connected to the power supply terminal 60 of the capacitive screen.
In the embodiment of the present application, since the source and the drain of the thin film transistor are completely symmetrical, the source and the drain of the fourth thin film transistor 303 and the fifth thin film transistor 304 described above are interchangeable.
Note that the dotted line in fig. 5 indicates the position touched by the user's finger.
In the embodiment of the present application, the reset switch 20 and the source follower 30 are implemented by 2 TFTs and 1 PMOS transistor. Therefore, the structural complexity of the pixel points can be reduced.
In addition to the fourth thin film transistor 303, the fifth thin film transistor 304, and the PMOS transistor 202, the first control unit 40 and the second control unit 50 may be the same control unit. Therefore, the number of the control units of the pixel points can be reduced, the wiring load of the capacitive screen is further reduced, and the signal to noise ratio of the pixel points is improved.
In one embodiment of the present application, the first electrodes 101 of different pixels in the capacitive screen are independent of each other, and the second electrodes 102 of different pixels are independent of each other.
In another embodiment, since the first electrodes 101 of the pixels in the capacitive screen are all connected to the power end of the capacitive screen, the first electrodes 101 of different pixels in the capacitive screen can be conducted with each other. As shown in fig. 6, the first electrodes 101 of different pixels in the capacitive screen are conducted, and the second electrodes 102 of different pixels are independent.
It should be noted that fig. 6 illustrates the first electrodes 101 of different pixels in the capacitive screen as a whole. Fig. 6 illustrates 4 pixels.
In this application embodiment, because the first electrode of different pixel points switches on each other in the capacitive screen, then can only connect the first electrode of one of them pixel point on the power end of capacitive screen in the capacitive screen, can realize that each pixel point all is connected with the power end of capacitive screen, like this, can reduce the wiring load of capacitive screen to improve the SNR of pixel point, reduce the design degree of difficulty of capacitive screen simultaneously.
In order to avoid the too large interval between the pixel points, influence the sensing area of the mutual capacitance of the pixel points, and avoid the too small interval between the pixel points, influence the coupling of the electric field between the mutual capacitances of the pixel points, in an embodiment of the present application, as shown in fig. 6, the interval d between two adjacent pixel points in the capacitive screen is 5 um. And the length and width of the pixel points are the same, and the size is between 30um and 80 um.
It is understood that the interval between two adjacent pixels in the capacitive screen, and the length and width of the pixels can be set to other sizes.
In one embodiment, the reset switch 20 and the source follower 30 may be located offset from the mutual capacitance 10.
In another embodiment, the reset switch 20 and the source follower 30 are integrally formed, and the second electrode 102 is disposed on both sides of the first electrode 101. In this way, on the one hand, the area of the capacitive screen can be reduced, and on the other hand, the first electrode 101 can shield the second electrode 102 from the interference of the whole of the reset switch 20 and the source follower 30.
In the case where the whole of the reset switch 20 and the source follower 30 and the second electrode 102 are respectively disposed on both sides of the first electrode 101, the input terminal of the source follower 30 and the end of the reset switch 20 connected to the second electrode 102 are connected to the second electrode 102 through the through hole of the first electrode 101. Based on this, in one embodiment, as shown in fig. 6, the first electrode 101 in the capacitive screen is in a shape of a Chinese character hui.
Based on the above embodiments, the process structure of one pixel in the capacitive screen provided by the embodiment of the present application can be as shown in fig. 7. Specifically, the process adopts a Low Temperature Polysilicon (LTPS) process and 8 Mask (Mask) processes. The patterning of the TFT device is realized by Poly, Gate, ILD and SD 4 Mask, and in the pixel point containing 3 TFTs, the two sides of the first electrode 101 and the second electrode 102 are respectively isolated by adopting insulating layers. The number of masks is not limited to the above number because of the controllability of the process and the material selection.
Wherein, in FIG. 7, Glass refers to Glass; poly refers to polysilicon; GI refers to a Gate Insulator Gate insulating layer; gate refers to a Gate; ILD refers to Inter Layer Dielectric; SD refers to Source and Drain; metal refers to Metal layers corresponding to the first electrode and the second electrode; INS refers to insulating layer Insulator; 1st Metal refers to the first electrode; the 2nd Metal refers to the second electrode.
With reference to fig. 7, a schematic diagram of a pixel point model for sensing a fingerprint valley in a capacitive screen according to this embodiment is shown in fig. 8. Fig. 9 is a schematic diagram of a pixel point model for sensing fingerprint ridges in the capacitive screen according to this embodiment. The INS1 is preferably a Resin (Resin) material with a thickness of 1.5 to 3um for better planarization effect and shielding effect of the TFT at the lower end of the first electrode, while considering process feasibility; INS2 is preferably a low dielectric constant Resin material with a thickness of 1.5-3 um; the INS3 is used as a protective film layer on the surface of the capacitive screen, a Coating layer with better environmental reliability and electrostatic discharge (ES) protection effect can be selected, and the thickness can be selected from 3-50 um. Wherein, the higher the Coating layer thickness is, the better the protection effect is, but the effect of the fingerprint valley and fingerprint ridge image is influenced. The TX and RX shown in the figure are the first and second electrodes, respectively, and the metal material is not limited, and Indium Tin Oxide (ITO) is preferred.
On the basis of any one of the above embodiments, the capacitive screen provided by the embodiment of the application further includes a processing unit. The processing unit determines fingerprint information of a corresponding pixel according to the fingerprint signal output by the pixel output end.
The fingerprint information includes whether fingerprint ridges exist at corresponding pixels and whether fingerprint valleys exist.
In one embodiment, the processing unit determines the amplitude of the signal output from the output terminal of the pixel point, and determines that the corresponding pixel is a fingerprint ridge if the amplitude is greater than a preset value. And if the pixel value is less than or equal to the preset value and greater than 0, determining that the corresponding pixel is a fingerprint valley. In the case of being equal to 0, it is determined that neither fingerprint ridge nor fingerprint valley exists at the corresponding pixel.
Based on the content, the fingerprint image of the user can be obtained under the condition that the user touches the capacitive screen by combining each pixel point on the capacitive screen. The preset value can be obtained empirically or experimentally.
The embodiment also provides electronic equipment, and the electronic equipment comprises the capacitive screen provided by any one of the embodiments.
In this embodiment, the electronic device may be a fingerprint machine, a fingerprint lock, an intelligent terminal, or the like.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
While the present embodiments have been described with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiments described above, which are meant to be illustrative and not restrictive, and that various changes may be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A capacitive screen, wherein the capacitive screen is comprised of a plurality of pixels, the pixels comprising:
the mutual capacitor comprises a first electrode and a second electrode which are oppositely arranged, wherein the second electrode is a fingerprint contact electrode of the capacitive screen, and the first electrode is connected with a power supply end of the capacitive screen;
the reset switch is connected between the power supply end of the capacitive screen and the second electrode;
the input end of the source follower is connected with the second electrode, the output end of the source follower is the fingerprint signal output end of the pixel point, and the power supply end of the source follower is connected with the power supply end of the capacitive screen;
a first switch control signal output end of the first control unit is connected with a control end of the source follower;
and a second switch control signal output end of the second control unit is connected with the control end of the reset switch.
2. The capacitive screen of claim 1, wherein the source follower comprises a first thin film transistor and a second thin film transistor, and the reset switch is a third thin film transistor;
the drain electrode of the first thin film transistor is used as the output end of the source follower, the grid electrode of the first thin film transistor is used as the control end of the source follower, and the source electrode of the first thin film transistor is connected with the drain electrode of the second thin film transistor;
the grid electrode of the second thin film transistor is used as the input end of the source follower, and the source electrode of the second thin film transistor is used as the power supply end of the source follower;
the grid electrode of the third thin film transistor is used as the control end of the reset switch, the drain electrode of the third thin film transistor is connected with the second electrode, and the source electrode of the third thin film transistor is connected with the power supply end of the capacitive screen.
3. The capacitive screen of claim 1, wherein the source follower comprises: the reset switch is a PMOS tube;
the source electrode of the PMOS tube is connected with the power supply end of the capacitive screen, the grid electrode of the PMOS tube is used as the control end of the reset switch, and the drain electrode of the PMOS tube is connected with the second electrode;
a grid electrode of the fourth thin film transistor is used as a control end of the source follower, a drain electrode of the fourth thin film transistor is used as an output end of the source follower, and a source electrode of the fourth thin film transistor is connected with a drain electrode of the fifth thin film transistor;
and the grid electrode of the fifth thin film transistor is used as the input end of the source follower, and the source electrode of the fifth thin film transistor is connected with the power supply end of the capacitive screen.
4. The capacitive screen of claim 3, wherein the first control unit and the second control unit are the same control unit.
5. A capacitive screen according to claim 1 wherein the first electrodes in different pixel sites are electrically conductive and the second electrodes in different pixel sites are independent of each other.
6. The capacitive screen of claim 1, wherein the interval between two adjacent pixels is 5 um; the length and width of pixel are the same, and the size be with between 30um to 80 um.
7. The capacitive screen of claim 1, wherein the input terminal of the source follower and the end of the reset switch connected to the second electrode are connected to the second electrode through the through hole of the first electrode.
8. The capacitive screen of claim 1, wherein the control terminals of the reset switches of different pixels in the capacitive screen are connected to the output terminal of the second switch control signal of the same second control unit.
9. The capacitive screen of claim 1, further comprising a processing unit;
and the processing unit determines whether fingerprint information exists at the corresponding pixel position according to the fingerprint signal output by the pixel output end.
10. An electronic device, characterized in that the electronic device comprises a capacitive screen according to any of claims 1-9.
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| CN202010608883.XA CN111814632A (en) | 2020-06-29 | 2020-06-29 | Capacitive screen and electronic equipment |
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