CN111144386A

CN111144386A - Ultrasonic fingerprint detection sensor and fingerprint detection method

Info

Publication number: CN111144386A
Application number: CN202010076591.6A
Authority: CN
Inventors: 效烨辉; 潘圣莹; 程泰毅
Original assignee: Silead Inc
Current assignee: Silead Inc
Priority date: 2020-01-23
Filing date: 2020-01-23
Publication date: 2020-05-12
Also published as: CN113158737A

Abstract

The invention provides an ultrasonic fingerprint detection sensor and a fingerprint detection method, wherein the ultrasonic fingerprint detection sensor comprises a glass substrate; the ultrasonic pixel array is arranged on the glass substrate and comprises ultrasonic pixel units; the ultrasonic pixel unit comprises an ultrasonic sensor and an ultrasonic fingerprint detection circuit connected with the ultrasonic sensor; the ultrasonic fingerprint detection circuit comprises a first MOS tube, a second MOS tube and a third MOS tube and is used for receiving at least three corresponding time sequence control signals; the first MOS tube stores fingerprint peak signals output by the ultrasonic sensor in a first preset time interval under at least three time sequence control signals; the second MOS tube outputs a fingerprint peak signal in a second preset time interval; the third MOS tube resets the grid signal of the first MOS tube in a third preset time interval and raises the direct current potential of the grid of the first MOS tube in the first preset time interval. The ultrasonic fingerprint detection sensor provided by the embodiment of the invention has the advantages of simple process and low manufacturing cost.

Description

Ultrasonic fingerprint detection sensor and fingerprint detection method

Technical Field

The invention relates to the field of fingerprint detection ultrasonic sensors, in particular to an ultrasonic fingerprint detection sensor and a detection method thereof.

Background

The ultrasonic sensor is a sensor for converting an ultrasonic signal into other energy signals (usually, electric signals), and has the characteristics of high frequency, short wavelength, small diffraction phenomenon, good directivity, capability of being directionally propagated as a ray, and the like. The penetration of ultrasonic waves into liquids and solids is great, especially in sunlight-opaque solids. Based on the characteristics of ultrasonic waves, the ultrasonic sensor is widely applied.

Unlike traditional optical or capacitive fingerprint identification schemes, ultrasonic sensors used for underscreen fingerprint identification are more popular due to their more flexible environmental applications. Different from the optical fingerprint identification sensor which cannot be too thin due to the limitation of the light path, the ultrasonic sensor has no limitation, so that the under-screen fingerprint identification sensor can be more easily thinned along with the thinning of electronic products. The ultrasonic sensor is not like a capacitance fingerprint sensor and is susceptible to influence on the sensitivity of the sensor due to the influence on the humidity of the environment.

As users seek better experience, areas capable of performing fingerprint identification are also expected to be larger, and a large-area fingerprint identification chip is sought at present. The ultrasonic fingerprint chip with a large area array manufactured by using the CMOS process is obviously weaker in cost advantage.

At present, the large-area-array under-screen ultrasonic fingerprint identification module in China is still in a development stage, and such an under-screen ultrasonic fingerprint identification sensor does not appear.

Disclosure of Invention

Based on the foregoing defects in the prior art, embodiments of the present invention provide a large-area array ultrasonic fingerprint detection sensor and a detection method thereof, where the ultrasonic fingerprint detection sensor can be manufactured by using a TFT process, and the process is relatively mature and the cost is relatively low.

In order to achieve the above object, the present invention provides the following technical solutions.

An ultrasonic fingerprint detection sensor comprising:

a glass substrate;

the ultrasonic pixel array is arranged on the glass substrate and comprises a plurality of ultrasonic pixel units; each of the ultrasonic pixel units includes: the ultrasonic fingerprint detection circuit is electrically connected with the ultrasonic sensor; each ultrasonic fingerprint detection circuit comprises at least three MOS tubes: the MOS transistor comprises a first MOS transistor, a second MOS transistor and a third MOS transistor; each ultrasonic fingerprint detection circuit receives at least three corresponding time sequence control signals respectively, and the at least three time sequence control signals are independent;

the first MOS tube stores fingerprint peak signals output by the ultrasonic sensor in a first preset time interval under at least three time sequence control signals; the second MOS tube outputs fingerprint peak signals stored in the first MOS tube in a second preset time interval under at least three time sequence control signals; the third MOS tube resets the grid signal of the first MOS tube in a third preset time interval under at least three time sequence control signals; and the third MOS tube raises the direct current potential of the grid electrode of the first MOS tube in the first preset time interval under at least three time sequence control signals.

A method for detecting a fingerprint by using the ultrasonic fingerprint detection sensor according to the above embodiment includes:

a first detection stage, providing an excitation signal, applying the excitation signal to the ultrasonic pixel array, and generating an ultrasonic signal by the ultrasonic pixel array;

in the second detection stage, an ultrasonic sensor in each ultrasonic pixel unit of the ultrasonic pixel array provides a detected fingerprint signal to the ultrasonic fingerprint detection circuit for detection;

providing the at least three sequential control signals to control the ultrasonic fingerprint detection circuit to perform fingerprint detection: wherein, among the three sequential control signal control ultrasonic wave fingerprint detection circuit: the first MOS tube stores the fingerprint signal output by the ultrasonic sensor in the first preset time interval; the second MOS tube outputs the fingerprint signal stored in the first MOS tube within the second preset time interval; the third MOS tube resets the grid signal of the first MOS tube in the third preset time interval; and the third MOS tube raises the direct current potential of the grid electrode of the first MOS tube within the first preset time interval.

In summary, in the ultrasonic fingerprint detection sensor according to the embodiment of the present invention, when the ultrasonic fingerprint detection circuit includes at least three MOS transistors and at most four MOS transistors, the same function as that of the ultrasonic fingerprint detection sensor including not only MOS transistors and capacitors but also diodes in the prior art can be achieved. Therefore, the ultrasonic fingerprint detection circuit provided by the embodiment of the invention has fewer types and numbers of electronic components, and greatly reduces the preparation process and cost. In addition, the ultrasonic fingerprint detection sensor provided by the embodiment of the invention can be used for manufacturing each electronic component on the glass substrate by adopting a TFT (thin film transistor) process, so that the preparation of the ultrasonic fingerprint detection sensor with a large area array can be realized.

In the embodiment that the ultrasonic fingerprint detection circuit only comprises three MOS tubes, at least one electronic component is saved compared with the prior art that the ultrasonic fingerprint detection sensor generally comprises three MOS tubes and one diode. Therefore, the area or the size of the ultrasonic fingerprint detection circuit of the embodiment of the invention is reduced, and the number of the ultrasonic fingerprint detection circuits which can be arranged on the glass substrate in unit area is more. Therefore, the pixel density of the ultrasonic fingerprint detection sensor can be improved, and the fingerprint identification efficiency and quality are improved, so that the method is very favorable.

In the embodiment that the ultrasonic fingerprint detection circuit includes four MOS pipes, through adjusting the time sequence control signal, can make this electronic component of fourth MOS pipe realize signal reset and voltage to the grid of first MOS pipe and raise these two kinds of functions, the flexibility of circuit preferred.

In addition, the fourth MOS pipe can avoid basically not using the electric leakage problem that the first MOS pipe grid that the diode arouses appears to can keep apart first MOS pipe and ultrasonic sensor, avoid external factor's influence, the output of fingerprint signal or the influence that reads the process and do not receive external noise factors such as finger or external world guarantee the authenticity of the fingerprint signal of output.

Drawings

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes, the proportional sizes, and the like of the respective members in the drawings are merely schematic for facilitating the understanding of the present invention, and do not specifically limit the shapes, the proportional sizes, and the like of the respective members of the present invention. Those skilled in the art, having the benefit of the teachings of this invention, may choose from the various possible shapes and proportional sizes to implement the invention as a matter of case. In the drawings:

FIG. 1 is a schematic top view of an ultrasonic fingerprint detection sensor in accordance with one non-limiting embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of the ultrasonic fingerprint detection sensor shown in FIG. 1;

FIG. 3 is a schematic diagram of an ultrasonic pixel unit included in an ultrasonic fingerprint detection sensor according to a non-limiting embodiment of the present invention;

FIG. 4A is a circuit topology diagram of an ultrasonic fingerprint detection circuit in the ultrasonic fingerprint detection sensor in accordance with the first non-limiting embodiment of the present invention;

FIGS. 4B to 4E are circuit topology diagrams of an ultrasonic fingerprint detection circuit in an ultrasonic fingerprint detection sensor according to a second non-limiting embodiment of the present invention;

FIG. 5 is a timing diagram illustrating the control of the ultrasonic fingerprint detection circuit shown in FIG. 4A;

fig. 6 is a control timing diagram of the ultrasonic fingerprint detection circuit shown in fig. 4B to 4E.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a single embodiment.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The embodiment of the invention provides an ultrasonic fingerprint detection sensor and a method for detecting a fingerprint by using the ultrasonic fingerprint detection sensor. The ultrasonic fingerprint detection sensor can be applied to electronic equipment such as but not limited to mobile smart phones, tablet electronic equipment, computers, GPS navigators, personal digital assistants and intelligent wearable equipment, is used for fingerprint identification, and can realize fingerprint unlocking, user identity verification, authority acquisition and the like.

For example, in a possible implementation scenario, the ultrasonic fingerprint detection sensor is configured in the smart phone, and the smart phone may obtain fingerprint feature information of the user based on the ultrasonic fingerprint detection sensor, so as to match the fingerprint feature information with stored fingerprint information, so as to implement identity verification of the current user, and thus determine whether the smart phone has a corresponding right to perform related operations such as screen unlocking, user identity verification, right acquisition, and the like on the smart phone.

As shown in fig. 1 to 3, the ultrasonic fingerprint detection sensor includes a glass substrate 1 and an ultrasonic pixel array 2 disposed on the glass substrate 1, where the ultrasonic pixel array 2 includes a plurality of ultrasonic pixel units 201. The plurality of ultrasonic wave pixel units 201 can be arranged on the glass substrate 1 in a regular form of multiple rows and multiple columns, so that the surface setting space of the glass substrate 1 is fully utilized, and the setting density of the ultrasonic wave pixel units 201 is improved. The glass substrate 1 may be a substrate on which a TFT process is performed, and the ultrasonic pixel unit 201 is formed on the glass substrate 1 by processing and manufacturing the conductive film.

Furthermore, the glass substrate 1 can be further provided with pins 3 for connecting with other IC chips and an ASIC control chip, so that the connection of the ultrasonic fingerprint detection sensor and other IC chips, the power supply and the signal control are realized.

As shown in fig. 2 and 3, each ultrasonic pixel unit 201 includes an ultrasonic Sensor (Sensor) and an ultrasonic fingerprint detection circuit 201a electrically connected to the ultrasonic Sensor. Specifically, the ultrasonic sensor includes a bottom electrode 201b (electrode), and the ultrasonic fingerprint detection circuit 201a is connected to the ultrasonic sensor through the bottom electrode 201 b.

As shown in fig. 1 and 2, the ultrasonic sensor may include a piezoelectric material 4, an electrode 5, a protective film 6, and a cover 7, which are stacked in this order from bottom to top. The cover layer 7 may be a cover glass, for being pressed or touched by a finger of a user. The protective film 6 isolates the electrode 5 from the cover layer 7, can buffer the pressing or touch operation of a user finger, and protects the electrode 5 and the piezoelectric material 4, the ultrasonic pixel array 2 and other structures on the lower layer.

In actual operation, the electrodes 5 are connected to an ac voltage, and after receiving an ac excitation voltage signal (excitation signal), the piezoelectric material 4 is triggered to vibrate, generating an ultrasonic signal at an ultrasonic frequency, which is emitted (TX) towards the user's finger pressing on the cover 7, thereby creating a stable or standard ultrasonic field. When the user's finger presses the cover plate 7, the standard wave field originally established by the ultrasonic signal changes due to the intervention of the user's finger, specifically including at least one of the amplitude, frequency or phase of the ultrasonic signal changes. As shown in fig. 2, an air gap is formed between the fingerprint valley of the finger and the outer surface of the sensor, and the fingerprint ridge is attached to the outer surface of the sensor. Then, the amplitude, frequency, or phase of the ultrasonic signal incident on the fingerprint valley is less varied, and the amplitude, frequency, or phase of the ultrasonic signal incident on the fingerprint ridge is less varied. The piezoelectric material 4 can receive and sense (RX) the above-mentioned changes of the ultrasonic field due to the intervention or disturbance of the user's finger and convert the changed acoustic signals into electrical fingerprint signals. The piezoelectric material 4 further supplies the converted fingerprint electric signal to the ultrasonic fingerprint detection circuit 201a electrically connected thereto through the bottom electrode 201 b.

In one embodiment, the ultrasonic sensor is time-shared as a transmitting unit of ultrasonic waves and a receiving unit of ultrasonic waves. That is, the ultrasonic sensor of the embodiment of the present invention transmits only the ultrasonic waves or receives only the ultrasonic waves during the same period of time. Alternatively, when the ultrasonic sensor is transmitting ultrasonic waves, the ultrasonic waves are not received. Accordingly, when the ultrasonic wave is received, the ultrasonic wave is not transmitted.

Specifically, when the electrodes 5 receive the excitation voltage signal, the whole area array of the piezoelectric material 4 is triggered to vibrate to generate the ultrasonic signal. When the fingerprint signal needs to be detected, the piezoelectric material 4 receives and transmits the change of the ultrasonic wave field, and outputs the fingerprint electric signal to the ultrasonic pixel array 2 covered under the piezoelectric material according to a preset rule. Since the ultrasound pixel array 2 includes the ultrasound pixel units 201 arranged in an array form, the "predetermined rule" may include: the fingerprint electric signals are output according to rows or the fingerprint electric signals are output according to columns.

Wherein outputting the fingerprint electric signal by a line may further include: only one row of fingerprint electric signals are output each time, and the fingerprint electric signals of all the rows are sequentially output according to time sequence. Or outputting the fingerprint electric signals of n rows each time, and sequentially outputting the fingerprint electric signals of all the rows according to time sequence. In this way, as shown in fig. 2, the ultrasonic pixel array 2 may receive a Row selection signal Row and control a manner in which the piezoelectric material 4 outputs a fingerprint electrical signal to the ultrasonic pixel array 2 based on the Row selection signal Row.

Similarly, the column-wise output of the fingerprint electrical signals can be explained with reference to the following description.

In the present embodiment, several ultrasonic pixel units 201 are independent of each other. The term "independent" means that there is no signal connection or signal sharing relationship between the ultrasonic pixel units 201, and the ultrasonic fingerprint detection circuit 201a only receives the electrical signal transmitted from the corresponding ultrasonic sensor. That is, each ultrasonic pixel cell 201 acts as a separate or independent working unit, and the respective ultrasonic pixel cells 201 do not interfere with each other during operation.

It should be noted that the layout shape (layout) of the ultrasonic pixel unit 201 according to the embodiment of the present invention is not limited to the rectangle or the square illustrated in fig. 3, and may include any other feasible shape, which is not limited by the present embodiment.

Each ultrasonic fingerprint detection circuit 201a includes at least three MOS transistors, and specifically, the number of the MOS transistors included in each ultrasonic fingerprint detection circuit 201a may be only three, or may be more than three. As shown in fig. 4A, in a possible embodiment, each ultrasonic fingerprint detection circuit 201a may include only three MOS transistors, namely, a first MOS transistor M1, a second MOS transistor M2, and a third MOS transistor M3. In another possible embodiment, as shown in fig. 4B to 4E, each ultrasonic fingerprint detection circuit 201a further includes a fourth MOS transistor M4 on the basis that the above-mentioned embodiment includes three MOS transistors, i.e., each ultrasonic fingerprint detection circuit 201a includes four MOS transistors.

In this embodiment, all the MOS transistors are preferably the same type of MOS transistor, such as N-type MOS transistor or P-type MOS transistor. Therefore, the number of the types of the electronic components is small, and the preparation complexity of the detection circuit is reduced. Of course, the type of the MOS transistor is not limited thereto, and in other possible embodiments, the MOS transistor may be an N-type MOS transistor, and a part of the MOS transistors may be P-type MOS transistors, which is not limited in the present invention.

Each ultrasonic fingerprint detection circuit 201a receives at least three corresponding sequential control signals respectively, and the at least three sequential control signals are independent to control the working states of at least three MOS tubes. The at least three corresponding timing control signals received by each ultrasonic fingerprint detection circuit 201a may be that the at least three timing control signals received by the same ultrasonic fingerprint detection circuit 201a are only used for operating at least three MOS transistors included in the controller, the timing control signals received by any two ultrasonic fingerprint detection circuits 201a do not have a crossing or sharing relationship, and each ultrasonic fingerprint detection circuit 201a works independently. By such a design, the situation of error accumulation caused by the crossing or sharing of the timing control signal between two or more ultrasonic fingerprint detection circuits 201a can be avoided.

As shown in fig. 4A, in the embodiment including only three MOS transistors, the number of timing control signals is also three. In one possible implementation scenario, the three timing control signals are: a ROW selection signal ROW connected with the gate of the second MOS transistor M2, a first driving signal OD _1(OverDrive) connected with the gate and input of the third MOS transistor M3, and a Bias signal Bias.

In the embodiment in which all three MOS transistors are N-type MOS transistors as illustrated in fig. 4A, the drain of the second MOS transistor M2 serves as an input electrode connected to the gate of the first MOS transistor M1, and the source serves as an output electrode for outputting the fingerprint peak signal. The source of the third MOS transistor M3 is an input terminal for receiving the Bias signal Bias, and the drain is an output terminal connected to the gate of the first MOS transistor M1. The connection relationship of the three MOS tubes and the ultrasonic sensor is as follows: the first MOS transistor M1 and the third MOS transistor M3 are connected in series, the ultrasonic sensor is connected between the first MOS transistor M1 and the third MOS transistor M3, and the first MOS transistor M1, the third MOS transistor M3, the third MOS transistor M3 and the third MOS transistor M1 share one connection point. The method specifically comprises the following steps: the gate of the first MOS transistor M1 is connected to the ultrasonic sensor and the drain of the third MOS transistor M3, the source is connected to the drain of the second MOS transistor M2, and the drain is connected to a constant voltage dc power Vcc. The source of the second MOS transistor M2 is used to output a signal Dn, which is a fingerprint signal stored in the gate of the first MOS transistor M1.

The voltage value of the constant voltage dc power Vcc may be set and selected according to actual conditions, for example, may be selected from 6V to 12V, and the function thereof is to make the first MOS transistor M1 always operate in the saturation region, so that the first MOS transistor M1 forms a Source Follower (Source Follower). In this way, the signal stored in the gate of the first MOS transistor M1 can be output from the source of the second MOS transistor M2 when the second MOS transistor M2 is turned on or turned on.

The timing control signal input and the structural connection relationship when the three MOS transistors are all N-type MOS transistors are described above, but the present embodiment is not limited thereto. When three MOS pipes are P type MOS pipes, three sequential control signals: the ROW selection signal ROW, the first driving signal OD _1 and the Bias signal Bias are respectively connected to the gate of the second MOS transistor M2, the gate of the third MOS transistor M3 and the drain thereof. The structure connection relation is as follows: the gate of the first MOS transistor M1 is connected to the ultrasonic sensor and the source of the third MOS transistor M3, the drain is connected to the source of the second MOS transistor M2, and the source is connected to a constant-voltage dc power supply Vcc.

In the embodiment that all three MOS transistors are P-type MOS transistors, the source of the second MOS transistor M2 is used as the input electrode connected to the gate of the first MOS transistor M1, and the drain is used as the output electrode for outputting the fingerprint peak signal. The drain of the third MOS transistor M3 is an input terminal for receiving the Bias signal Bias, and the source is an output terminal connected to the gate of the first MOS transistor M1.

In the embodiment illustrated in fig. 4B to 4E including four MOS transistors, the number of timing control signals is also four, which are respectively: the ROW selection signal ROW is connected with the grid electrode of the second MOS tube M2, the first driving signal OD _1 and the Bias signal Bias are connected with the grid electrode and the input electrode of the third MOS tube M3, and the second driving signal OD _2 is connected with the grid electrode of the fourth MOS tube M4.

Similarly, in the embodiment in which the four MOS transistors are N-type MOS transistors as illustrated in fig. 4B to 4D, the drain of the second MOS transistor M2 is used as the input electrode connected to the gate of the first MOS transistor M1, and the source is used as the output electrode for outputting the fingerprint peak signal. The source of the third MOS transistor M3 is an input terminal for receiving the Bias signal Bias, and the drain is an output terminal connected to the gate of the first MOS transistor M1. Four timing control signals: the ROW selection signal ROW, the first driving signal OD _1, the Bias signal Bias, and the second driving signal OD _2 are respectively connected to the gate of the second MOS transistor M2, the gate and the source of the third MOS transistor M3, and the gate of the fourth MOS transistor M4. The connection relationship between the four MOS tubes and the ultrasonic sensor is as follows: in addition to the three MOS transistors, the fourth MOS transistor M4 is disposed between the first MOS transistor M1 and the ultrasonic sensor. The fourth MOS transistor M4 is connected in series with the third MOS transistor M3, the ultrasonic sensor is connected between the third MOS transistor M3 and the fourth MOS transistor M4, and the third MOS transistor M4, the third MOS transistor M3 and the fourth MOS transistor M4 share one connection point. Specifically, the drain of the fourth MOS transistor M4 is connected to the gate of the first MOS transistor M1, and the source is connected to the ultrasonic sensor and the drain of the third MOS transistor M3.

In the embodiment of the four MOS transistors, which are P-type MOS transistors as illustrated in fig. 4E, the source of the second MOS transistor M2 is used as the input electrode connected to the gate of the first MOS transistor M1, and the drain is used as the output electrode for outputting the fingerprint peak signal. The drain of the third MOS transistor M3 is an input terminal for receiving the Bias signal Bias, and the source is an output terminal connected to the gate of the first MOS transistor M1. Four timing control signals: the ROW selection signal ROW, the first driving signal OD _1, the Bias signal Bias, and the second driving signal OD _2 are respectively connected to the gate of the second MOS transistor M2, the gate and the drain of the third MOS transistor M3, and the gate of the fourth MOS transistor M4. The connection relationship between the four MOS tubes and the ultrasonic sensor is as follows: the gate of the first MOS transistor M1 is connected to the source of the fourth MOS transistor M4, the drain is connected to the source of the second MOS transistor M2, and the source is connected to a constant-voltage dc power supply Vcc. The drain of the fourth MOS transistor M4 is connected to the ultrasonic sensor and the source of the third MOS transistor M3.

Referring to fig. 5 and 3, under at least three timing control signals, that is, within a time range of the at least three timing control signals, the first MOS transistor M1 stores a fingerprint peak signal output by the ultrasonic sensor in a first predetermined time interval, the second MOS transistor M2 outputs a fingerprint peak signal stored in the first MOS transistor M1 in a second predetermined time interval, and the third MOS transistor M3 resets (Reset) a gate signal of the first MOS transistor M1 in a third predetermined time interval, so as to raise a dc potential of the gate of the first MOS transistor M1 in the first predetermined time interval.

In the above description, the at least three timing control signals are the ROW selection signal ROW connected to the gate of the second MOS transistor M2, the first driving signal OD _1 and the Bias signal Bias connected to the gate and the input of the third MOS transistor M3, and the second driving signal OD _2 connected to the gate of the fourth MOS transistor M4, respectively.

The timing control signal ROW connected to the gate of the second MOS transistor M2 controls the second MOS transistor M2 to be turned on or off, so as to control whether the fingerprint signal stored in the gate of the first MOS transistor M1 is output. Specifically, when the voltage of the ROW selection signal ROW is at a high level, the second MOS transistor M2 is turned on. When the voltage of the ROW selection signal ROW is at a low level, the second MOS transistor M2 is turned off.

It should be noted that the high level and the low level are voltage thresholds for turning on and off the MOS transistor, respectively, and may be set according to actual situations, for example, the high level is 0 to 17V, further may be 0 to 15V, and the low level is 0V. The above explanation and numerical definition of the high and low levels are applicable to the on or off condition of all MOS transistors related to the present invention.

The two timing control signals, the first driving signal OD _1 and the Bias signal Bias, connecting the gate of the third MOS transistor M3 and the other pole can control the third MOS transistor M3 to turn on or off, so as to control whether to raise the potential of the gate of the first MOS transistor M1 or to reset the signal at the gate of the first MOS transistor M1. Specifically, when the voltage value of the first driving signal OD _1 is greater than the voltage value of the Bias signal Bias, or when the voltage value of the first driving signal OD _1 is at a high level and the voltage value of the Bias signal Bias is at a low level, the third MOS transistor M3 is turned on. When the voltage value of the first driving signal OD _1 is smaller than the voltage value of the Bias signal Bias, or the voltage of the first driving signal OD _1 is at a low level, the voltage of the Bias signal Bias is at a high level, and the third MOS transistor M3 is turned off.

Accordingly, the timing control signal (the second driving signal OD _2) connected to the gate of the fourth MOS transistor M4 can control the fourth MOS transistor M4 to turn on or off. Similarly, when the voltage of the second driving signal OD _2 is high or low, the second MOS transistor M2 is in an on or off state, respectively.

In combination, it can be known that the ultrasonic fingerprint detection circuit 201a according to the embodiment of the present invention includes only two electronic components, i.e., a MOS transistor and a capacitor C1, and does not include other types of electronic components, such as a diode. Therefore, the function for raising the gate voltage or current of the first MOS transistor M1 needs to be performed by the MOS transistor. This requires the ability to do without a diode but still achieve a raised potential and also requires that the leakage be controlled to the same order as the diode leakage.

The following describes a process of detecting a fingerprint using the ultrasonic fingerprint detection sensor according to the above-described embodiment of the present invention.

Specifically, the voltage values of at least three timing control signals are adjusted, so that the first MOS transistor M1 stores a fingerprint peak signal output by the ultrasonic sensor in a first preset time interval, the second MOS transistor M2 outputs a fingerprint peak signal stored in the first MOS transistor M1 in a second preset time interval, the third MOS transistor M3 resets a gate signal of the first MOS transistor M1 in a third preset time interval, and the dc potential of the gate of the first MOS transistor M1 is raised in the first preset time interval. That is, the first MOS transistor M1 stores the fingerprint peak signal, and the gate dc potential thereof is raised, which is completed in the same time interval.

The voltage Δ V of the fingerprint peak signal is weak in general and is difficult to be detected accurately. Therefore, in a further embodiment, the voltage values of at least three timing control signals within the first preset time interval may be adjusted, so that the first MOS transistor M1 stores the fingerprint peak signal output by the ultrasonic sensor, and the third MOS transistor M3 raises the dc potential signal of the gate of the first MOS transistor M1. Namely: after the voltage of the third MOS transistor M3 is boosted, the voltage of the signal stored in the gate of the first MOS transistor M1 is converted from the voltage of the original fingerprint peak signal to the voltage of the fingerprint peak signal and the boosted value provided by the third MOS transistor M3.

Accordingly, the voltage values of the at least three timing control signals within the second preset time interval are adjusted, so that the second MOS transistor M2 outputs the fingerprint peak signal stored in the first MOS transistor M1, and the third MOS transistor M3 raises the dc potential signal at the gate of the first MOS transistor M1. That is, at this time, the voltage value of the signal output by the second MOS transistor M2 is the fingerprint signal voltage stored in the gate of the first MOS transistor M1 after boosting. Therefore, the voltage value of the output fingerprint signal is improved, and subsequent detection is facilitated.

As shown in fig. 4A, in the embodiment including only three MOS transistors, the third preset time interval corresponds to the time interval T1 in fig. 5. At this time, the ROW selection signal ROW and the Bias signal Bias are in a low level state, the first driving signal OD _1 is in a high level state, and the voltage value of the first driving signal OD _1 is greater than that of the Bias signal Bias. Accordingly, the second MOS transistor M2 is turned off, and the third MOS transistor M3 is turned on. At this time, the voltage of the gate of the first MOS transistor M1 may be reset to be equal to the voltage of the Bias signal Bias.

Specifically, if the Bias signal Bias is Reset voltage, the third MOS transistor M3 can Reset (Reset or Reset) the gate of the first MOS transistor M1, and the fingerprint signal at the gate of the first MOS transistor M1 is cleared. The value of the Reset voltage may be set and selected according to actual conditions, for example, may be 0V, and this embodiment does not limit this.

The first predetermined time interval corresponds to the time interval T2 in fig. 5. At this time, the ROW selection signal ROW is maintained at a low level, and accordingly, the second MOS transistor M2 is still maintained in an off state. The voltage values of the first driving signal OD _1 and the Bias signal Bias are reduced synchronously, and the voltage values of the two reduced signals are equal. The third MOS transistor M3 forms a diode-like structure at this time.

Further, the first driving signal OD _1 and the Bias signal Bias each include a first boosting pulse in a first predetermined time interval, the start time, the sustain time and the voltage value of the two first boosting pulses are the same, and the sustain time of the first boosting pulse is T0. The third MOS transistor M3 raises the voltage signal of the gate of the first MOS transistor M1 under the action of the first boost pulse, and the voltage signal of the raised gate of the first MOS transistor M1 is the sum of the voltage value of the fingerprint peak signal and the voltage value of the first boost pulse.

Referring to fig. 5, in practice, at a certain time node within the first preset time interval, the ultrasonic sensor transmits back the fingerprint signal. At the same time, the first driving signal OD _1 and the Bias signal Bias generate a high pulse in a short time, i.e., a first boosting pulse. Since the third MOS transistor M3 is equivalent to a diode-like transistor during the whole first predetermined time interval, when the first driving signal OD _1 and the Bias signal Bias generate high pulse signals, the voltage at the gate of the first MOS transistor M1 can be raised, and the raised voltage is maintained due to the unidirectional current limiting effect of the third MOS transistor M3 (diode-like transistor). Therefore, the gate voltage of the first MOS transistor M1 is raised from the fingerprint peak signal voltage Δ V to Vdc1+ Δ V, where Vdc1 is the voltage value of the first boost pulse of the Bias signal Bias.

If the third MOS transistor M3 does not raise the voltage of the gate of the first MOS transistor M1, after the ultrasonic sensor returns the fingerprint signal, the voltage value of the gate of the first MOS transistor M1 is only the voltage Δ V of the fingerprint peak signal returned by the ultrasonic sensor. After the first driving signal OD _1 and the Bias signal Bias generate high pulses and the third MOS transistor M3 forms a diode-like structure, the gate voltage of the first MOS transistor M1 may be raised to Vdc1+ Δ V.

As described above, the voltage Δ V of the fingerprint peak signal is weak and difficult to be detected accurately. Therefore, by controlling the voltage values of the first driving signal OD _1 and the Bias signal Bias, the third MOS transistor M3 forms a diode-like structure within a first preset time interval, and the first driving signal OD _1 and the Bias signal Bias generate a high pulse within a short time to raise the signal voltage at the gate of the first MOS transistor M1, so that the voltage of the fingerprint signal to be output subsequently is higher, which is beneficial to subsequent reading and detection.

The second preset time interval corresponds to the time interval T3 in fig. 5, at which the ROW selection signal ROW is in a high state, and the second MOS transistor M2 is turned on. And the first driving signal OD _1 maintains the low level, the Bias signal Bias switches to the high level, and the voltage value of the first driving signal OD _1 is smaller than that of the Bias signal Bias, so that the third MOS transistor M3 is turned off. Thus, the gate signal stored in the first MOS transistor M1 is output through the second MOS transistor M2.

In the embodiment with only three MOS transistors, as shown in fig. 4A and 5, the specific process of completing a row of fingerprint detection by the ultrasonic fingerprint detection sensor is as follows:

in a time interval T1 (a third preset time interval), the ROW selection signal ROW is at a low voltage, and the second MOS transistor M2 is turned off. The first driving signal OD _1 is at a high level, the Bias signal Bias is at a low voltage, and the third MOS transistor M3 is turned on. If the Bias signal Bias is Reset voltage, the third MOS transistor M3 performs the Reset function to clear the fingerprint signal at the gate of the first MOS transistor M1.

During the time interval T2 (the first predetermined time interval), the levels of the first driving signal OD _1 and the Bias signal Bias are decreased, and the voltages of the two signals are kept equal. At this time, the third MOS transistor M3 functions as a diode-like transistor. While the ultrasonic sensor returns the fingerprint signal, the first driving signal OD _1 and the Bias signal Bias generate a first boost pulse for a short time. The third MOS transistor M3 is functionally equivalent to a diode at this time, so that the voltage of the gate of the first MOS transistor M1 can be raised, the voltage of the gate of the first MOS transistor M1 is raised from the fingerprint peak signal voltage Δ V to Vdc1+ Δ V, and the raised fingerprint peak signal is stored in the gate of the first MOS transistor M1 to wait for subsequent output.

In a time interval T3 (a second preset time interval), the ROW selection signal ROW is switched to a high level, the first driving signal OD _1 and the Bias signal Bias are in a low level state, the second MOS transistor M2 is turned on, and the third MOS transistor M3 is turned off. The gate signal (fingerprint signal with the voltage raised) stored in the first MOS transistor M1 is output via the second MOS transistor M2.

In order to prevent the loss of the fingerprint signal over time due to leakage in the stage of reading or outputting the fingerprint signal at the time interval T3, after the gate signal voltage of the first MOS transistor M1 is raised, the low level of the first driving signal OD _1 is maintained, and the Bias signal Bias is raised to the high level, so that the third MOS transistor M3 is turned off in principle. At this time, although the third MOS transistor M3 still has leakage, simulation verification shows that the leakage amount can be controlled to be in the magnitude of pA, which is substantially equal to the magnitude of leakage when a diode is reversely biased in the prior art, thereby meeting design requirements.

In summary, in the embodiment including only three MOS transistors, the fingerprint signal after voltage boosting is finally obtained, and the specific voltage of the fingerprint signal is the sum of the fingerprint peak signal Δ V output by the ultrasonic sensor and the voltage value Vdc1 of the first boosting pulse.

As shown in fig. 4B to 4E, in the embodiment including four MOS transistors, each ultrasonic fingerprint detection circuit 201a receives four timing control signals independent of each other. Further, in order to avoid that external factors such as a user's finger, an external environment, etc. affect the fingerprint signal of the gate of the first MOS transistor M1 in the process of outputting the fingerprint signal by the second MOS transistor M2 in the second preset time interval, the voltage values of the four timing control signals in the second preset time interval may be isolated by the fourth MOS transistor M4 from the first MOS transistor M1 and the ultrasonic sensor.

In this way, during the second predetermined time interval, i.e. during the process of reading or outputting the fingerprint signal, the fourth MOS transistor M4 is used to isolate the ultrasonic sensor, which may be interfered by external factors, from the first MOS transistor M1. In this way, the noise signal generated by the ultrasonic sensor due to the interference of the external environment is prevented from being transmitted to the gate of the first MOS transistor M1, thereby improving the quality of the output fingerprint signal.

Further, the third MOS transistor M3 outputs an electrical signal for resetting the gate of the first MOS transistor M1 through the fourth MOS transistor M4 during the third predetermined time interval and the fourth predetermined time interval under the four timing control signals. The third preset time interval and the fourth preset time interval respectively correspond to the time interval T1 and the time interval T5 in fig. 3, and may be named as a first reset time interval and a second reset time interval, respectively. That is, in this embodiment, the gate signal of the first MOS transistor M1 needs to be reset or reset twice. The reset to the gate potential of the first MOS transistor M1 in the third preset time interval may be a global reset, and the reset to the gate potential of the first MOS transistor M1 in the fourth preset time interval may be a local reset.

In a third predetermined time interval, the ROW selection signal ROW and the Bias signal Bias are at a low level, and the first driving signal OD _1 and the second driving signal OD _2 are at a high level. The second MOS transistor M2 is turned off, and the third MOS transistor M3 and the fourth MOS transistor M4 are turned on. Since the fourth MOS transistor M4 is connected in series between the first MOS transistor M1 and the second MOS transistor M2, the fourth MOS transistor M4 at this time is equivalent to a wire. Therefore, the voltage of the gate of the first MOS transistor M1 can be reset to be equal to the voltage of the Bias signal Bias.

Similarly, if the Bias signal Bias is Reset voltage, the third MOS transistor M3 can perform Reset action on the gate of the first MOS transistor M1, and the fingerprint signal at the gate of the first MOS transistor M1 is cleared.

The first predetermined time interval corresponds to the time interval T2 in fig. 6. At this time, the ROW selection signal ROW is maintained at a low level, and the second MOS transistor M2 is in an off state. And the voltage value of the first driving signal OD _1 decreases to be equal to the voltage value of the Bias signal Bias. The third MOS transistor M3 forms a diode-like structure at this time.

Furthermore, the first driving signal and the bias signal each include a second boost pulse within a first preset time interval, the start time, the sustain time, and the voltage value of the two second boost pulses are the same, and the sustain time of the second boost pulse is T7. The third MOS transistor M3 raises the voltage signal of the gate of the first MOS transistor M1 under the action of the second boost pulse, and the raised voltage of the gate of the first MOS transistor M1 is the sum of the voltage value of the fingerprint peak signal and the voltage value of the second boost pulse.

Referring to fig. 6, in practice, at a certain time node within the first preset time interval, the ultrasonic sensor transmits back the fingerprint signal. At this time, the first driving signal OD _1 and the Bias signal Bias generate a high pulse in a short time, i.e., a second boosting pulse. Since the third MOS transistor M3 is equivalent to a diode-like transistor during the whole first predetermined time interval, the voltage at the gate of the first MOS transistor M1 can be raised, and the raised voltage is maintained due to the unidirectional current limiting effect of the third MOS transistor M3 (diode-like transistor). Therefore, the gate voltage of the first MOS transistor M1 is raised from the fingerprint peak signal voltage Δ V to Vdc2+ Δ V, where Vdc2 is the voltage value of the second boost pulse of the Bias signal Bias.

The second predetermined time interval also includes two sub-time intervals, which respectively correspond to the sub-time interval T4 and the sub-time interval T6 in fig. 6 and are named as a first reading time interval and a second reading time interval, respectively. That is, in this embodiment, it is also necessary to perform an operation of reading or outputting the fingerprint signal stored at the gate of the first MOS transistor M1 twice. The boosted gate potential of the first MOS transistor M1 is read or output in the sub-time interval T4, and the reset gate signal of the first MOS transistor M1 is read or output in the sub-time interval T6.

In the sub-time interval T4, when the ROW selection signal ROW is at a high level and the second MOS transistor M2 is turned on, the fingerprint signal (specifically, the fingerprint signal after voltage boosting, whose voltage value is the sum of the voltage value Δ V of the fingerprint peak signal and the voltage value Vdc2 of the second boost pulse) stored in the gate of the first MOS transistor M1 is output through the second MOS transistor M2.

In the process, to avoid the influence of the external factors, the fourth MOS transistor M4 is used to isolate the ultrasonic sensor, which may be interfered by the external factors, from the first MOS transistor M1. Specifically, the second driving signal OD _2 is at a low level, and the fourth MOS transistor M4 is turned off, so as to block the connection between the ultrasonic sensor and the first MOS transistor M1 and prevent the noise signal from being transmitted to the gate of the first MOS transistor M1. The third MOS transistor M3 is in an off state or an on state, which is not limited in this embodiment.

After the first reading is completed, a second reset or reset operation is required to be performed on the first MOS transistor M1. As shown in fig. 6, the time interval T5, i.e., the fourth preset time interval, is a secondary or partial reset execution time period. In this time interval, the ROW selection signal ROW is at a low level, and the second MOS transistor M2 is turned off. The second driving signal OD _2 is high, and the fourth MOS transistor M4 is turned on, which corresponds to a conductive line. The first driving signal OD _1 switches to a high level, and the voltage value is greater than the voltage value of the Bias signal Bias. The voltage value of the Bias signal Bias at this time is slightly lower than the voltage value Vdc2 of the second boosting pulse. The third MOS transistor M3 is turned on, and the voltage at the gate of the first MOS transistor M1 is reset to be equal to the voltage value of the Bias signal Bias.

Subsequently, the voltage values of the four timing control signals in the fifth preset time interval are adjusted, so that the second MOS transistor M2 outputs an electrical signal for resetting the gate of the first MOS transistor M1 by the third MOS transistor M3. The fifth predetermined time interval is the second reading time interval described above, and corresponds to the time interval T6 in fig. 6. That is, the electrical signal stored in the gate output by the second MOS transistor M2 in the fifth preset time interval is the electrical signal that the gate of the first MOS transistor M1 is reset in the fourth preset time interval.

In this time interval, the voltage value of the first driving signal OD _1 is greater than the voltage value of the Bias signal Bias, and the third MOS transistor M3 is turned off. The ROW select signal ROW is high, and the second MOS transistor M2 is turned on, thereby outputting the voltage signal stored in the gate of the first MOS transistor M1. The voltage signal at this time is an electrical signal that the gate of the first MOS transistor M1 is reset within a fourth preset time interval, and is slightly smaller than the voltage value Vdc2 of the second boosting pulse. Therefore, the voltage value Δ V of the fingerprint peak signal can be obtained by performing difference processing on the fingerprint signal stored in the first MOS transistor M1 output in the second predetermined time interval and the signal of the gate potential of the first MOS transistor M1 in the fourth predetermined time interval. Specifically, the voltage Vdc2+ Δ V of the superimposed fingerprint signal output at the time of the first reading is subtracted by the reset voltage output after the second reset.

Through the secondary reset, the fingerprint signal which is output in the second preset time interval and stored in the first MOS transistor M1 and the potential signal which is output in the fifth preset time interval and stored in the grid electrode of the first MOS transistor M1 are subjected to difference processing, the influence of other factors on the fingerprint signal in the detection process can be filtered, and the background noise is reduced.

With reference to fig. 4B to 4E and fig. 6, in the embodiment including four MOS transistors, the specific process of completing a row of fingerprint detection by the ultrasonic fingerprint detection sensor is as follows:

in a time interval T1 (a third preset time interval), the ROW selection signal ROW is at a low voltage, and the second MOS transistor M2 is turned off. The first driving signal OD _1 and the second driving signal OD _2 are at high level, the Bias signal Bias is at low voltage, the third MOS transistor M3 and the fourth MOS transistor M4 are turned on, and the fourth MOS transistor M4 is equivalent to a conductive wire. If the Bias signal Bias is Reset voltage, the third MOS transistor M3 performs the Reset function to clear the fingerprint signal at the gate of the first MOS transistor M1.

During a time interval T2 (a first predetermined time interval), the ROW selection signal ROW is still maintained at a low level, and the second MOS transistor M2 is in an off state. The voltage value of the first driving signal OD _1 is decreased to be equal to the voltage value of the Bias signal Bias, and at this time, the third MOS transistor M3 forms a diode-like structure. While the ultrasonic sensor returns the fingerprint signal, the first driving signal OD _1 and the Bias signal Bias generate a second boost pulse for a short time. Since the third MOS transistor M3 now functions as a diode-like transistor, the voltage at the gate of the first MOS transistor M1 can be raised. Namely, the grid voltage of the first MOS transistor M1 is raised to Vdc2+ Δ V from the fingerprint peak signal voltage Δ V, and the raised fingerprint peak signal is stored in the grid of the first MOS transistor M1 to wait for subsequent output.

The time interval T3 is located before the first time reading time interval T4 in time sequence, and since the time for reading data is long, in order to prevent the fingerprint signal stored in the gate of the first MOS transistor M1 from losing with time due to leakage, and to isolate the influence of external factors, the fourth MOS transistor M4 is turned off by reducing the potential of the second driving signal OD _2, so as to isolate the first MOS transistor M1 from the ultrasonic sensor.

In a time interval T4 (a first time reading time interval included in a second preset time interval), the ROW selection signal ROW is switched to a high level, the second MOS transistor M2 is turned on, and the fingerprint signal stored at the gate of the first MOS transistor M1 after the voltage is raised is output through the second MOS transistor M2. In addition, in this process, the second driving signal OD _2 is maintained at a low level, and the fourth MOS transistor M4 is maintained at an off state, so as to block the connection between the ultrasonic sensor and the first MOS transistor M1 and prevent the noise signal from being transmitted to the gate of the first MOS transistor M1.

Subsequently, a secondary or local reset is performed. In the sub-time interval T5 (the fourth preset time interval), the ROW selection signal ROW is switched to the low level, and the second MOS transistor M2 is turned off. The second driving signal OD _2 is switched to a high level, and the fourth MOS transistor M4 is turned on, which corresponds to a conductive line. The first driving signal OD _1 switches to a high level, and the voltage value is greater than the voltage value of the Bias signal Bias. The voltage value of the Bias signal Bias at this time is slightly lower than the voltage value Vdc2 of the second boosting pulse. The third MOS transistor M3 is turned on, and the voltage at the gate of the first MOS transistor M1 is reset to be equal to the voltage value of the Bias signal Bias.

Finally, a second reading is taken. In a time interval T6 (a fifth preset time interval), the voltage value of the first driving signal OD _1 is controlled to be greater than the voltage value of the Bias signal Bias, and the third MOS transistor M3 is turned off. The ROW selection signal ROW is switched to a high level to turn on the second MOS transistor M2, and the voltage signal stored in the gate of the first MOS transistor M1 is output, and the voltage signal at this time is a reset voltage signal. The voltage value Δ V of the fingerprint peak signal can be obtained by combining the voltage values of the fingerprint signals outputted during the time interval T4.

In summary, in the embodiment including four MOS transistors, the fingerprint signal obtained finally is the difference between the voltages outputted twice, and the fingerprint signal is closer to the actual real fingerprint peak signal.

Further, as shown in fig. 4A to 4E, each ultrasonic fingerprint detection circuit 201a may further include a capacitor C1, the capacitor C1 having two poles: a first pole and a second pole. The first pole is connected with the gate of the first MOS transistor M1. The capacitor C1 holds the signal stored at the gate of the first MOS transistor M1 for a first predetermined time interval under at least three timing control signals. That is, when the second MOS transistor M2 is in the off state and the gate of the first MOS transistor M1 stores the peak fingerprint signal, the capacitor C1 is configured to hold the peak fingerprint signal stored at the gate of the first MOS transistor M1, so as to reduce loss of the fingerprint signal during the storage process.

As shown in fig. 4B and 4E, in a possible embodiment, the second pole of the capacitor C1 may be connected to a ROW selection signal ROW, which raises the voltage of the gate of the first MOS transistor M1.

However, as can be seen from the above description, in the embodiment including four MOS transistors, since the time period (the time interval T3 shown in fig. 6) for the gate of the first MOS transistor M1 to need to hold the signal is not consistent with the time period (i.e., the second preset time interval, or the time interval T4 shown in fig. 6) for the ROW selection signal ROW to be turned on, the ROW selection signal ROW may not be able to function in the time period for the gate of the first MOS transistor M1 to need to hold the signal.

Therefore, as shown in fig. 4C, to solve the above problem, in another possible embodiment, the second pole of the capacitor C1 can be connected to a dc potential V2, and the voltage of the gate of the first MOS transistor M1 is directly raised by the dc potential V2.

Similarly, the voltage value of the dc potential V2 in this embodiment is difficult to determine, and if the voltage value of the dc potential V2 is too small, the gate voltage of the first MOS transistor M1 is not raised significantly. If the voltage value of the dc voltage V2 is too large, the voltage at the gate of the first MOS transistor M1 will be raised to a level that may overwrite the stored fingerprint signal. Therefore, the effect of this embodiment is difficult to control.

To further address the above problem, in yet another possible embodiment, as shown in fig. 4A and 4D, the second pole of the capacitor C1 is selected to be grounded. In this embodiment, the capacitor C1 is grounded, so that the function of the capacitor C1 becomes pure and single, only the capacitor C1 holds the fingerprint signal stored at the gate of the first MOS transistor M1, and the function of raising the gate voltage of the first MOS transistor M1 is performed by the third MOS transistor M3. Thus, a control signal can be reduced, and the control logic of the current is more clear and simple.

In summary, in the ultrasonic fingerprint detection sensor according to the embodiment of the present invention, when the ultrasonic fingerprint detection circuit 201a includes at least three MOS transistors and at most four MOS transistors, the same function as that of the ultrasonic fingerprint detection sensor including not only the MOS transistors and the capacitor C1 but also the diode in the prior art can be achieved. Therefore, the ultrasonic fingerprint detection circuit 201a of the embodiment of the invention has fewer types and numbers of electronic components, and greatly reduces the preparation process and cost. In addition, the ultrasonic fingerprint detection sensor provided by the embodiment of the invention can be used for manufacturing each electronic component on the glass substrate by adopting a TFT (thin film transistor) process, so that the preparation of the ultrasonic fingerprint detection sensor with a large area array can be realized.

In the embodiment where the ultrasonic fingerprint detection circuit 201a includes only three MOS transistors, at least one electronic component is omitted, compared to the prior art ultrasonic fingerprint detection sensor which generally includes three MOS transistors and one diode. Accordingly, the area or size of the ultrasonic fingerprint detection circuit 201a according to the embodiment of the present invention is reduced, and the number of the ultrasonic fingerprint detection circuits 201a that can be disposed on a unit area of the glass substrate is increased. Therefore, the pixel density of the ultrasonic fingerprint detection sensor can be improved, and the fingerprint identification efficiency and quality are improved, so that the method is very favorable.

In the embodiment that the ultrasonic fingerprint detection circuit 201a includes four MOS transistors, by adjusting the timing control signal, the electronic component of the fourth MOS transistor M4 can implement two functions of signal reset and voltage raising for the gate of the first MOS transistor M1, and the flexibility of the circuit is better.

In addition, the fourth MOS transistor M4 can substantially avoid the problem of leakage of the gate of the first MOS transistor M1 caused by not using a diode, and can isolate the first MOS transistor M1 from the ultrasonic sensor, thereby avoiding the influence of external factors, preventing the output or reading process of the fingerprint signal from being influenced by external noise factors such as fingers or the outside, and ensuring the authenticity of the output fingerprint signal.

The embodiment of the invention provides a method for detecting a fingerprint by using the ultrasonic fingerprint detection sensor, which comprises the following steps:

in the first detection stage, an excitation signal is provided and applied to the ultrasonic pixel array 2, and the ultrasonic pixel array 2 generates an ultrasonic signal.

As described above, the ultrasonic pixel array 2 includes an ultrasonic sensor including the piezoelectric material 4 and the electrode 5, and an Excitation Signal (Excitation Signal) is applied to the electrode 5 to trigger the piezoelectric material 4 to vibrate to generate an ultrasonic Signal.

In the second detection stage, the ultrasonic sensor in each ultrasonic pixel unit 201 of the ultrasonic pixel array 2 supplies the detected fingerprint signal to the ultrasonic fingerprint detection circuit 201a for detection.

The ultrasonic signal generated by the ultrasonic pixel array 2 creates a stable or standard ultrasonic field, when the user's finger presses the cover plate 7, the standard ultrasonic field originally created by the ultrasonic signal is changed due to the finger's intervention or interference, the piezoelectric material 4 can receive and sense (RX) the ultrasonic field, and convert the changed acoustic signal into an electric fingerprint signal, and then the changed electric fingerprint signal can be provided to the ultrasonic fingerprint detection circuit 201a201a electrically connected with the bottom electrode 201 b.

At least three timing control signals are provided to control the ultrasonic fingerprint detection circuit 201a to perform fingerprint detection. Wherein, among the three sequential control signal control ultrasonic wave fingerprint detection circuit:

the first MOS tube M1 stores the fingerprint signal output by the ultrasonic sensor in a first preset time interval;

the second MOS tube M2 outputs the fingerprint signal stored in the first MOS tube M1 in a second preset time interval;

the third MOS transistor M3 resets the gate signal of the first MOS transistor M1 within a third preset time interval;

the third MOS transistor M3 raises the dc potential of the gate of the first MOS transistor M1 within a first preset time interval.

The specific process of the first MOS transistor M1, the second MOS transistor M2, and the third MOS transistor M3 performing the above steps under the control of at least three timing control signals may refer to the above description, and is not repeated herein. In one embodiment, the first detection phase is controlled to occur before the second detection phase. That is, the ultrasonic wave pixel array 2 firstly generates an ultrasonic wave signal, and then detects the change of a wave field established by the ultrasonic wave signal under the condition that a user finger intervenes, and a fingerprint signal is obtained according to the change.

Further, in the step of controlling the ultrasonic fingerprint detection circuit 201 a: the second MOS transistor M2 outputs the potential signal stored in the gate of the first MOS transistor within a fifth predetermined time interval. Correspondingly, the fingerprint signal stored in the first MOS transistor M1 output in the second preset time interval and the potential signal stored in the gate of the first MOS transistor M1 in the fifth preset time interval are subjected to difference processing.

As described above, the potential signal stored in the gate of the first MOS transistor M1 output in the fifth preset time interval may be a voltage signal reset for the second time, and the fingerprint signal stored in the first MOS transistor M1 output in the second preset time interval may be a boosted voltage signal, specifically Vdc2+ Δ V. Through the secondary reset, the fingerprint signal which is output in the second preset time interval and stored in the first MOS transistor M1 and the potential signal which is output in the fifth preset time interval and stored in the grid electrode of the first MOS transistor M1 are subjected to difference processing, the influence of other factors on the fingerprint signal in the detection process can be filtered, and the background noise is reduced.

Furthermore, a reset time zone is separated from the second preset time zone in the fifth preset time zone, and the reset time zone is the fourth preset time zone. In the reset time zone, the gate signal of the first MOS transistor M1 is reset to a dc potential, which is recorded as Va. And finally, subtracting the direct current potential from the boosted voltage signal to obtain the Vdc2+ delta V-Va as the fingerprint signal through difference processing.

It should be noted that, in the description of the present invention, the terms "first", "second", and the like are used for descriptive purposes only and for distinguishing similar objects, and no precedence between the two is considered as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.

Any numerical value recited herein includes all values from the lower value to the upper value that are incremented by one unit, provided that there is a separation of at least two units between any lower value and any higher value. For example, if it is stated that the number of a component or a value of a process variable such as voltage is from 0 to 17, preferably from 0 to 15, then the intention is that equivalents such as 0 to 14, 0.1 to 13, 1 to 12 are not expressly recited in this specification. For values less than 1, one unit is suitably considered to be 0.0001, 0.001, 0.01, 0.1. These are only examples of what is intended to be explicitly recited, and all possible combinations of numerical values between the lowest value and the highest value that are explicitly recited in the specification in a similar manner are to be considered.

Unless otherwise indicated, all ranges include the endpoints and all numbers between the endpoints. The use of "about" or "approximately" with a range applies to both endpoints of the range. Thus, "about 20 to about 30" is intended to cover "about 20 to about 30", including at least the endpoints specified.

The above description is only a few embodiments of the present invention, and those skilled in the art can make various changes or modifications to the embodiments of the present invention according to the disclosure of the application document without departing from the spirit and scope of the present invention.

Claims

1. An ultrasonic fingerprint detection sensor, comprising:

a glass substrate;

2. The ultrasonic fingerprint detection sensor according to claim 1, wherein the first MOS transistor stores a fingerprint peak signal output by the ultrasonic sensor in the first preset time interval, and the third MOS transistor raises a dc potential signal of the gate of the first MOS transistor.

3. The ultrasonic fingerprint detection sensor of claim 1, wherein each of the ultrasonic fingerprint detection circuits further comprises: a fourth MOS transistor; the fourth MOS grid is correspondingly connected with a time sequence control signal; the fourth MOS tube isolates the first MOS tube from the ultrasonic sensor within the second preset time interval under the four sequential control signals.

4. The ultrasonic fingerprint detection sensor according to claim 3, wherein said third MOS transistor is connected in series with a fourth MOS transistor, and said ultrasonic sensor is connected between said third MOS transistor and said fourth MOS transistor.

5. The ultrasonic fingerprint detection sensor according to claim 3, wherein the third MOS transistor outputs an electrical signal for resetting the gate of the first MOS transistor within a third predetermined time interval and a fourth predetermined time interval under four timing control signals.

6. The ultrasonic fingerprint detection sensor according to any one of claims 1 to 5, wherein at least three of the timing control signals are respectively: a row selection signal, a bias signal and a first driving signal; the row selection signal is connected with the grid electrode of the second MOS tube, and the bias signal is connected with the source electrode of the third MOS tube; the first driving signal is connected with the grid electrode of the third MOS tube.

7. The ultrasonic fingerprint detection sensor of claim 6, wherein each of the ultrasonic fingerprint detection circuits further comprises: a capacitor; the capacitor keeps the signals stored by the grid electrode of the first MOS tube in the first preset time interval under at least three timing control signals.

8. The ultrasonic fingerprint detection sensor according to claim 7, wherein two ends of said capacitor are respectively connected to the gate of said first MOS transistor and said row selection signal.

9. The ultrasonic fingerprint detection sensor of claim 7, wherein a first pole of the capacitor is connected to a gate of the first MOS transistor, and a second pole of the capacitor is connected to a dc potential.

10. The ultrasonic fingerprint detection sensor of claim 7, wherein a first pole of the capacitor is connected to the gate of the first MOS transistor and a second pole is connected to ground.

11. The ultrasonic fingerprint detection sensor of claim 1, wherein all MOS transistors are N-type MOS transistors; or all the MOS tubes are P-type MOS tubes.

12. The ultrasonic fingerprint detection sensor according to claim 1, wherein said ultrasonic sensor is time-shared as a transmission unit of ultrasonic waves and a reception unit of ultrasonic waves.

13. A method for fingerprint sensing using the ultrasonic fingerprint sensing sensor according to claim 1, comprising:

providing the at least three sequential control signals to control the ultrasonic fingerprint detection circuit to perform fingerprint detection: wherein, among the three sequential control signal control ultrasonic wave fingerprint detection circuit:

the first MOS tube stores the fingerprint signal output by the ultrasonic sensor in the first preset time interval;

the second MOS tube outputs the fingerprint signal stored in the first MOS tube within the second preset time interval;

the third MOS tube resets the grid signal of the first MOS tube in the third preset time interval;

and the third MOS tube raises the direct current potential of the grid electrode of the first MOS tube within the first preset time interval.

14. The method of claim 13, wherein controlling the first detection phase occurs before the second detection phase.

15. The method of claim 13, wherein controlling the ultrasonic fingerprint detection circuit:

the second MOS tube outputs a potential signal stored in the grid electrode of the first MOS tube within a fifth preset time interval;

and performing difference processing on the fingerprint signal which is output in the second preset time interval and stored in the first MOS tube and the grid potential signal which is output in the fifth preset time interval and stored in the first MOS tube.

16. The method of claim 15, wherein a reset time zone is separated between the fifth preset time interval and the second preset time interval, and the gate signal of the first MOS transistor is reset to a dc potential in the reset time zone.