Fingerprint identification component, fingerprint identification method and fingerprint identification device

This is a National Phase Application filed under 35 U.S.C. 371 as a national stage of PCT/CN2019/078854, filed on Mar. 20, 2019, an application claiming priority to Chinese patent application No. 201810326891.8, filed on Apr. 12, 2018, the entire contents of which are incorporated herein by reference.

The present disclosure relates to the field of fingerprint identification technologies, and in particular, to a fingerprint identification component, a fingerprint identification method, and a fingerprint identification device.

Fingerprints are inherent and unique features of a human body that are distinguishable from other people. Fingerprints are composed of a series of valleys and ridges on the skin, and fingerprint identification technology developed from fingerprints is used as a technique for personal authentication early. Currently, relatively mature fingerprint detection techniques include: fingerprint identification based on optical imaging technology, fingerprint identification based on photosensitive sensors, fingerprint identification based on heat sensitive sensors, and fingerprint identification based on ultrasonic detection. Among them, fingerprint identification based on ultrasonic detection is a current popular research field.

The present disclosure provides a fingerprint identification component, a fingerprint identification method and a fingerprint identification device.

According to an embodiment of the present disclosure, there is provided a fingerprint identification component, including:

an ultrasonic wave transmission circuit configured to transmit an ultrasonic wave in a direction towards a fingerprint at an interval of a first time period in a detection phase;

an ultrasonic wave reception circuit configured to, in the detection phase, receive an ultrasonic wave reflected by the fingerprint, convert the ultrasonic wave into an electric signal, and output the electric signal to a signal reading line, in order for an external detection component to determine texture information of the fingerprint according to the electric signal in the signal reading line,

wherein the electrical signal has a frequency f satisfying

f = 1 t 1 + t 2 ,

where t 1 is a time duration spent for transmitting the ultrasonic wave once, and t 2 is the first time period.

According to an embodiment of the present disclosure, the ultrasonic wave transmission circuit includes: a first transistor, a second transistor, and an ultrasonic wave generation structure;

the ultrasonic wave generation structure has a first input terminal and a second input terminal, the first input terminal of the ultrasonic wave generation structure being coupled to a first power supply terminal;

a control electrode of the first transistor is coupled to a first control signal line, a first electrode of the first transistor is coupled to a second power supply terminal, and a second electrode of the first transistor is coupled to the second input terminal of the ultrasonic wave generation structure;

a control electrode of the second transistor is coupled to a second control signal line, a first electrode of the second transistor is coupled to the first power supply terminal, and a second electrode of the second transistor is coupled to the second input terminal of the ultrasonic wave generation structure; and

a voltage provided by the first power supply terminal is not equal to a voltage provided by the second power supply terminal.

According to an embodiment of the present disclosure, the ultrasonic wave generation structure includes: a first electrode, a second electrode and a first piezoelectric material layer, the first electrode is opposite to the second electrode, and the first piezoelectric material layer is between the first electrode and the second electrode; and

the first electrode is coupled to the first input terminal, and the second electrode is coupled to the second input terminal.

According to an embodiment of the present disclosure, the ultrasonic wave reception circuit includes: an ultrasonic wave conversion structure, a third transistor, a fourth transistor, a fifth transistor, a capacitor and a rectifier diode;

the ultrasonic wave conversion structure has a third input terminal and a first output terminal, wherein the third input terminal of the ultrasonic wave conversion structure is coupled to a third power supply terminal or grounded, and the first output terminal of the ultrasonic wave conversion structure is coupled to a first electrode of the rectifier diode;

a control electrode of the third transistor is coupled to a third control signal line, a first electrode of the third transistor is coupled to a fourth power supply terminal, and a second electrode of the third transistor, a second electrode of the rectifier diode, a first terminal of the capacitor and a control electrode of the fourth transistor are coupled to a first node;

a first electrode of the fourth transistor is coupled to a fifth power supply terminal, and a second electrode of the fourth transistor is coupled to a first electrode of the fifth transistor;

a control electrode of the fifth transistor is coupled to a read control signal line, and a second electrode of the fifth transistor is coupled to the signal reading line; and

a second terminal of the capacitor is grounded.

According to an embodiment of the present disclosure, the ultrasonic wave reception circuit further includes: a sixth transistor;

wherein a control electrode of the sixth transistor is coupled to a fourth control signal line, a first electrode of the sixth transistor is coupled to a sixth power supply terminal, and a second electrode of the sixth transistor is coupled to the first electrode of the rectifier diode.

According to an embodiment of the present disclosure, the ultrasonic wave conversion structure includes: a third electrode, a fourth electrode and a second piezoelectric material layer, wherein the third electrode is opposite to the fourth electrode, and the second piezoelectric material layer is between the third electrode and the fourth electrode; and

the third electrode is coupled to the third input terminal, and the fourth electrode is coupled to the first output terminal.

The present disclosure further provides a fingerprint identification device, including the fingerprint identification component as described above and a detection component.

According to an embodiment of the present disclosure, wherein the detection component is coupled to the ultrasonic wave reception circuit through the signal reading line; and

the detection component is configured to extract, from a signal transmitted by the signal reading line, the electric signal having the frequency f satisfying

f = 1 t 1 + t 2 ,

and identify valleys and ridges of the fingerprint according to the extracted electric signal.

The present disclosure further provides a fingerprint identification method, the method being performed by operating the above fingerprint identification component, and the fingerprint identification method includes:

in the detection phase, transmitting, by the ultrasonic transmission circuit, the ultrasonic wave in a direction towards a fingerprint at the interval of the first time period, and receiving the ultrasonic wave reflected by the fingerprint, converting the ultrasonic wave into the electric signal and outputting the electric signal to a signal reading line by the ultrasonic wave reception circuit; and extracting the electric signal from a signal transmitted by the signal reading line and determining texture information of the fingerprint according to the extracted electric signal by the external detection component.

According to an embodiment of the present disclosure, the detection phase includes output sub-phases and non-output sub-phases that alternate, wherein a time duration of each output sub-phase is t 1 , and a time duration of each non-output sub-phase is t 2 ;

the step of transmitting, by the ultrasonic wave transmission circuit, an ultrasonic wave in a direction towards a fingerprint at an interval of a first time period includes:

in the output sub-phase, turning on the first transistor under control of a first control signal provided by the first control signal line, and turning off the second transistor under control a second control signal provided by the second control signal line; and

in the non-output sub-phase, turning off the first transistor under control of a first control signal provided by the first control signal line, and turning on the second transistor under control of a second control signal provided by the second control signal line.

According to an embodiment of the present disclosure, before the detection phase, the method further includes: resetting, by the ultrasonic wave reception circuit, the electric signal received by the signal reading line.

FIG. 1 is a schematic structural diagram of a fingerprint identification component based on ultrasonic detection in the related art;

FIG. 2 is a schematic diagram of a voltage variation with time at a first node N 1 in FIG. 1 ;

FIG. 3 is a schematic diagram of a circuit configuration of a fingerprint identification component according to an embodiment of the present disclosure;

FIG. 4 is a schematic diagram of a circuit configuration of a fingerprint identification component according to another embodiment of the present disclosure;

FIG. 5 is a timing diagram illustrating operation of the fingerprint identification devices of FIGS. 3 and 4 ; and

FIG. 6 is a flowchart of a fingerprint identification method according to an embodiment of the present disclosure.

In order to make those skilled in the art better understand the technical solutions of the present disclosure, a fingerprint identification component, a fingerprint identification method and a fingerprint identification device provided in the present disclosure are described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic structural diagram of a fingerprint identification component based on ultrasonic detection in the related art, FIG. 2 is a schematic diagram of a voltage variation with time at a first node N 1 in FIG. 1 , and as shown in FIGS. 1 and 2 , the fingerprint identification component includes: an ultrasonic wave transmission circuit 1 and an ultrasonic wave reception circuit 2 . The ultrasonic wave transmission circuit 1 is configured to continuously transmit an ultrasonic wave in a direction towards a fingerprint in a detection phase P 2 , the ultrasonic wave reception circuit 2 is configured to receive the ultrasonic wave reflected by the fingerprint, convert the ultrasonic wave into an electrical signal, and transmit the electrical signal to an external detection component 3 through a signal reading line RL in the detection phase P 2 ; and the detection component 3 identifies valleys or ridges of the fingerprint from the received electrical signal.

According to the embodiments of the present disclosure, the term “fingerprint” may represent a fingerprint of a finger of a user, a toe print of a user, or other objects having a texture.

The following embodiments will be described in detail by taking fingerprint identification of a finger of a user as an example, but it should be understood by those skilled in the art that identification of a toe print and identification of texture information of other objects having a texture using the fingerprint identification component, the fingerprint identification method and the fingerprint identification device according to the embodiments of the present disclosure also belong to the protection scope of the present disclosure.

According to an embodiment of the present disclosure, the ultrasonic wave reception circuit 2 includes: an ultrasonic wave conversion structure 5 , a reset transistor Mrst, a source-follower transistor Msf, a reading transistor Msel, a rectifier diode PN and a capacitor CO. The operation process of the fingerprint identification component includes three phases: a reset phase P 1 , a detection phase P 2 , and a waiting phase P 3 .

In the reset phase P 1 , the reset transistor Mrst is turned on under the control of a signal supplied by a reset control signal line L_rst, and the reset transistor Mrst writes a reset voltage Vss supplied from a power supply terminal couple thereto to a first node N 1 .

In the detection phase P 2 (corresponding to a fixed time duration t), the ultrasonic wave transmission circuit 1 transmits an ultrasonic wave in a direction towards a finger of a user, the ultrasonic wave is reflected by a fingerprint of the finger of the user and emitted to the ultrasonic wave conversion structure 5 , the ultrasonic wave conversion structure 5 outputs a corresponding current according to the received ultrasonic wave, the current charges the first node N 1 through the rectifier diode PN, so that the voltage of the first node N 1 rises. In a case where the ultrasonic wave is reflected at a valley of the finger, the ultrasonic wave has a relatively weak intensity when reaching the ultrasonic wave conversion structure 5 because the movement distance of the ultrasonic wave is relatively long (as compared with a case where the ultrasonic wave is reflected at a ridge of the finger), the ultrasonic wave conversion structure 5 outputs a relatively small current, the voltage of the first node N 1 rises at a relatively small rate, and thus, the level of the voltage reached at the end of the detection phase P 2 is relatively low. In a case where the ultrasonic wave is reflected at a ridge of the finger, the ultrasonic wave has a relatively strong intensity when reaching the ultrasonic wave conversion structure 5 because the movement distance of the ultrasonic wave is relatively short (as compared with a case where the ultrasonic wave is reflected at a valley of the finger), the ultrasonic wave conversion structure 5 outputs a relatively large current, the voltage of the first node N 1 rises at a relatively large rate, and thus, the level of the voltage reached at the end of the detection phase P 2 is relatively high.

During the rising process of the voltage of the first node N 1 , the voltage of the second electrode of the source-follower transistor Msf rises in synchronization with the rise of the voltage of the first node N 1 . The reading transistor Msel is turned on under the control of a control signal output from a read control signal line SEL, and outputs a signal at the second electrode of the source-follower transistor Msf to the signal reading line RL.

Therefore, if the ultrasonic wave is reflected at a valley of a finger, the voltage received by the signal reading line RL at the end of the detection phase is relatively small; and if the ultrasonic wave is reflected at a ridge of a finger, the voltage received by the signal reading line RL at the end of the detection phase is relatively large. It is assumed that the voltage received by the signal reading line RL at the end of the detection phase is V 0 .

In the waiting phase P 3 , the reset transistor is turned on again, and the reset voltage is written to the first node N 1 again.

When the external detection component 3 identifies a valley or a ridge, it needs to first extract, from the signal reading line RL, the electrical signal output by the reading transistor Msel in the detection phase, then identifies the magnitude of the voltage V 0 corresponding to the electrical signal at the end of the detection phase, and finally compares the voltage V 0 with a preset reference voltage value. If the voltage V 0 is greater than the preset reference voltage value, it is indicated that the current output by the ultrasonic wave conversion structure 5 is large, the first node N 1 is charged quickly, and the fingerprint of the finger is a ridge; if the voltage V 0 is less than or equal to the preset reference voltage value, it is indicated that the current output by the ultrasonic wave conversion structure 5 is small, the first node N 1 is charged slowly, and the fingerprint of the finger is a valley.

However, it is found in practical applications that even if the ultrasonic wave is reflected at a ridge, the maximum value of the voltage V 0 corresponding to the electric signal output by the reading transistor Msel in the detection phase P 2 is only at the microvolt (μV) level, and the electric signal is easily submerged in noise (especially when the signal reading line RL has a large length) when being transmitted through the signal reading line RL, so that the detection component 3 cannot accurately extract the electric signal from the signal reading line RL, and in turn the subsequent accurate identification of the finger fingerprint as a valley or ridge based on the electric signal is affected.

That is, in the related art, because the ultrasonic echo signal is weak, the electrical signal output by the fingerprint identification component based on ultrasonic detection is weak. When the signal reading line for transmitting the electrical signal is long (e.g., when detecting a large-area fingerprint), the electrical signal in the signal reading line output by the fingerprint identification component is very easily interfered by the environment, and the electrical signal is submerged in noise, so that the detection component cannot accurately identify the electrical signal output by the fingerprint identification component, and in turn the identification accuracy is influenced.

In order to overcome the problem that the detection component cannot accurately extract the electric signal output by the ultrasonic wave reception circuit in the detection phase from the signal reading line due to the fact that the electric signal is relatively weak, the present disclosure provides a fingerprint identification component, a fingerprint identification method and a fingerprint identification device.

It should be noted that a transistor in the present disclosure has three electrodes: a control electrode, a first electrode and a second electrode, the control electrode is specifically a gate electrode of the transistor, one of the first electrode and the second electrode is a source electrode, and the other one is a drain electrode. In addition, in the following embodiments, exemplary descriptions are given by taking a case where the transistors are N-type transistors as an example, which do not limit the technical solution of the present disclosure; those skilled in the art should appreciate that replacing N-type transistors with P-type transistors to achieve the same function also falls within the protection scope of the present disclosure.

FIG. 3 is a schematic circuit diagram of a fingerprint identification component according to an embodiment of the present disclosure, and as shown in FIG. 3 , the fingerprint identification component includes: an ultrasonic wave transmission circuit 1 and an ultrasonic wave reception circuit 2 .

According to an embodiment of the present disclosure, the ultrasonic wave transmission circuit 1 is configured to transmit an ultrasonic wave in a direction towards a finger at an interval of a first time period (time elapsed from the end of transmission of the ultrasonic wave to the start of the next transmission of the ultrasonic wave) in the detection phase; the ultrasonic wave reception circuit 2 is configured to receive the ultrasonic wave reflected by the finger and convert the received ultrasonic wave into an electric signal in the detection phase. The electric signal having a frequency f satisfying

f = 1 t 1 + t 2 ,

where t 1 is a time duration spent for transmitting the ultrasonic wave once, and t 2 is the first time period.

The signal reading line RL transmits the electric signal output by the ultrasonic wave reception circuit 2 in the detection phase to the external detection component 3 , so that the detection component 3 can determine the texture information of the fingerprint of the finger according to the electric signal.

In the detection phase, the ultrasonic wave transmission circuit 1 transmits an ultrasonic wave at an interval of the first time period, the ultrasonic wave reception circuit 2 receives the ultrasonic wave at an interval of the first time period, and accordingly the electrical signal output by the ultrasonic wave reception circuit 2 has periodicity, i.e., the electrical signal has a certain frequency f, which satisfies

f = 1 t 1 + t 2 .

In this case, the external detection component 3 can accurately obtain the electrical signal output by the ultrasonic wave reception circuit 2 in the detection phase by only extracting, from the electrical signal transmitted through the signal reading line, part of the electrical signal having a frequency of

1 t 1 + t 2 ,

so as to ensure the subsequent accurate identification of a valley and a ridge of the fingerprint of the finger according to the extracted electrical signal.

Specifically, the voltage corresponding to the electrical signal extracted by the detection component 3 increases in a stepwise manner, and a valley and a ridge of the fingerprint of the finger can be accurately identified according to the maximum voltage (corresponding voltage at the end of the detection phase) corresponding to the electrical signal. The specific identification principle may refer to the foregoing description, and details thereof are not repeated here.

It should be noted that, by adjusting, in advance, the time duration t 1 spent for transmitting the ultrasonic wave once and the first time period t 2 during which the ultrasonic wave is not transmitted, the frequency of the electric signal output by the ultrasonic wave receiving circuit in the detection phase can be controlled.

The technical solutions of the present disclosure will be described in detail below in conjunction with specific examples. With continued reference to FIG. 3 , according to an embodiment of the present disclosure, the ultrasonic wave transmission circuit 1 includes: a first transistor M 1 , a second transistor M 2 , and an ultrasonic wave generation structure 4 . The ultrasonic wave generation structure 4 has a first input terminal and a second input terminal, and the first input terminal of the ultrasonic wave generation structure 4 is coupled to a first power supply terminal.

A control electrode of the first transistor M 1 is coupled to a first control signal line CL 1 , a first electrode of the first transistor M 1 is coupled to a second power supply terminal, and a second electrode of the first transistor M 1 is coupled to the second input terminal of the ultrasonic wave generation structure 4 .

A control electrode of the second transistor M 2 is coupled to a second control signal line CL 2 , a first electrode of the second transistor M 2 is coupled to a first power supply terminal, and a second electrode of the second transistor M 2 is coupled to the second input terminal of the ultrasonic wave generation structure 4 .

The voltage provided by the first power supply terminal is not equal to the voltage provided by the second power supply terminal. For example, the voltage supplied by the first power supply terminal may be a high level, and the voltage supplied by the second power supply terminal may be a low level. Alternatively, the voltage supplied by the first power supply terminal may be a low level, and the voltage supplied by the second power supply terminal may be a high level.

According to an embodiment of the present disclosure, the ultrasonic wave generation structure 4 includes: a first electrode 401 , a second electrode 402 , and a first piezoelectric material layer 403 , the first electrode 401 being disposed opposite to the second electrode 402 , and the first piezoelectric material layer 403 being positioned between the first electrode 401 and the second electrode 402 . The first electrode 401 is coupled to the first input terminal, or the first electrode 401 may serve as the first input terminal, the second electrode 402 is coupled to the second input terminal, or the second electrode 402 may serve as the second input terminal.

In the embodiment, exemplary description is given by taking a case where the first power supply terminal supplies a low-level operating voltage Vss and the second power supply terminal supplies a high-level operating voltage Vdd as an example. When the first transistor M 1 is turned on and the second transistor M 2 is turned off, the first electrode 401 receives a low-level operating voltage Vss, the second electrode 402 receives a high-level operating voltage Vdd, and the first piezoelectric material layer 403 oscillates to generate and emit an ultrasonic wave. When the first transistor M 1 is turned off and the second transistor M 2 is turned on, the low-level operating voltage Vss is input to both the first electrode 401 and the second electrode 402 , and the first piezoelectric material layer 403 generates no ultrasonic wave. Therefore, by controlling the first transistor M 1 and the second transistor M 2 to be turned on/off, whether the ultrasonic wave generation structure 4 generates an ultrasonic wave or not can be controlled.

According to an embodiment of the present disclosure, the ultrasonic wave reception circuit 2 includes: an ultrasonic wave conversion structure 5 , a third transistor M 3 , a fourth transistor M 4 , a fifth transistor M 5 , a capacitor C and a rectifier diode PN.

The ultrasonic wave conversion structure 5 has a third input terminal and a first output terminal, the third input terminal of the ultrasonic wave conversion structure is coupled to a third power supply terminal or is grounded (the case of being grounded is not shown), and the first output terminal of the ultrasonic wave conversion structure 5 is coupled to a first electrode (e.g., anode) of the rectifier diode PN.

A control electrode of the third transistor M 3 is coupled to a third control signal line CL 3 , a first electrode of the third transistor M 3 is coupled to a fourth power supply terminal, and a second electrode of the third transistor M 3 , a second electrode (e.g., cathode) of the rectifier diode PN, a first terminal of the capacitor C, and a control electrode of the fourth transistor M 1 are coupled to a first node N 1 .

A first electrode of the fourth transistor M 4 is coupled to a fifth power supply terminal, and a second electrode of the fourth transistor M 4 is coupled to a first electrode of the fifth transistor M 5 .

A control electrode of the fifth transistor M 5 is coupled to a read control signal line SEL, and a second electrode of the fifth transistor M 5 is coupled to the signal reading line RL; the second terminal of the capacitor C is grounded.

According to an embodiment of the present disclosure, the ultrasonic wave conversion structure 5 includes: a third electrode 501 , a fourth electrode 502 and a second piezoelectric material layer 503 , the third electrode 501 being disposed opposite to the fourth electrode 502 , and the second piezoelectric material layer 503 being positioned between the third electrode 501 and the fourth electrode 502 . The third electrode 501 is coupled to the third input terminal and the fourth electrode 502 is coupled to the first output terminal.

After the ultrasonic wave conversion structure 5 receives an ultrasonic wave, due to the direct piezoelectric effect, an alternating current signal having the same frequency as the received ultrasonic wave signal is generated at the first output terminal, and due to the existence of the rectifier diode PN (with a PN junction), only a positive current passes through the rectifier diode PN and charges the first node N 1 , so that the voltage of the first node N 1 rises at a speed positively correlated with the magnitude of the positive current. In a case where the ultrasonic wave conversion structure 5 does not receive an ultrasonic wave, the first node N 1 does not discharge through the ultrasonic wave conversion structure 5 due to the existence of the PN junction; and in the meanwhile, the capacitor C can keep the voltage at the first node N 1 stable.

The operating process of the fingerprint identification component shown in FIG. 3 will be described in detail below with reference to the accompanying drawings. The third power supply terminal and the fourth power supply terminal both are supplied with a low-level operating voltage Vss, and the fifth power supply terminal is supplied with a high-level operating voltage Vdd.

FIG. 5 is a timing diagram illustrating operation of the fingerprint identification device component in FIGS. 3 and 4 , and as shown in FIG. 5 , one operation cycle of the fingerprint identification component includes three phases: a reset phase P 1 , a detection phase P 2 , and a waiting phase P 3 .

In the reset phase P 1 , the first control signal provided by the first control signal line CL 1 is at a low level, the second control signal provided by the second control signal line CL 2 is at a low level, the third control signal provided by the third control signal line CL 3 is at a high level, and the read control signal provided by the read control signal line SEL is at a low level (or may be at a high level).

At this time, both the first transistor M 1 and the second transistor M 2 are turned off, and the ultrasonic wave generation structure 4 does not emit an ultrasonic wave. The third transistor M 3 is turned on, and the low-level operating voltage Vss supplied by the fourth power supply terminal is written to the first node N 1 through the third transistor M 3 , so that the first node N 1 is reset.

It should be noted that, in the reset phase P 1 , because the voltage at the node N 1 is the low-level operating voltage Vss, the fourth transistor M 4 is turned off. Therefore, regardless of whether the read control signal provided by the read control signal line SEL is at a low level or a high level, the electric signal in the signal reading line RL is always at a low level, that is, the electric signal received by the signal reading line RL is also reset.

The detection phase P 2 includes output sub-phases and non-output sub-phases that alternate, each output sub-phase has a time duration of t 1 , each non-output sub-phase has a time duration of t 2 , and t 1 and t 2 may be equal or unequal.

In the output sub-phase, the first control signal provided by the first control signal line CL 1 is at a high level, the second control signal provided by the second control signal line CL 2 is at a low level, the third control signal provided by the third control signal line CL 3 is at a low level, and the read control signal provided by the read control signal line SEL line is at a high level.

At this time, the first transistor M 1 is turned on, the second transistor M 2 is turned off, the ultrasonic wave generation structure 4 emits an ultrasonic wave, the ultrasonic wave is reflected by a fingerprint of a finger and then transmitted to the ultrasonic wave conversion structure 5 , the ultrasonic wave conversion structure 5 generates a corresponding current according to the intensity of the received ultrasonic wave, and charges the first node N 1 through the rectifier diode PN, the voltage of the first node N 1 rises, the voltage of the second electrode of the fourth transistor M 4 rises synchronously with the voltage of the first node N 1 , and the fifth transistor M 5 outputs the signal at the second electrode of the fourth transistor M 4 to the signal reading line RL.

In the non-output sub-phase, the first control signal provided by the first control signal line CL 1 is at a low level, the second control signal provided by the second control signal line CL 2 is at a high level, the third control signal provided by the third control signal line CL 3 is at a low level, and the read control signal provided by the read control signal line SEL is at a high level.

At this time, the first transistor M 1 is turned off, the second transistor M 2 is turned on, the ultrasonic wave generation structure 4 does not emit an ultrasonic wave, and the ultrasonic wave conversion structure 5 does not output a current. The capacitor C keeps the voltage of the first node N 1 stable.

In the entire detection phase P 2 , the output sub-phases alternate with the non-output sub-phases, the voltage at the first node N 1 rises in a stepwise manner, and the voltage of the electrical signal output to the signal reading line RL rises in a stepwise manner, and the electrical signal has a frequency satisfying

f = 1 t 1 + t 2 .

At the end of the detection phase, the voltage of the electrical signal is V 0 .

In the waiting phase P 3 , the first control signal provided by the first control signal line CL 1 is at a low level, the second control signal provided by the second control signal line CL 2 is at a low level, the third control signal provided by the third control signal line CL 3 is first at a high level and then switched to a low level, and the read control signal provided by the read control signal line SEL is at a high level.

Both the first transistor M 1 and the second transistor M 2 are turned off, and therefore the ultrasonic wave generation structure 4 does not emit an ultrasonic wave.

During the initial period of the waiting phase P 3 , because the third control signal provided by the third control signal line CL 3 is at a high level, the third transistor M 3 is turned on, at this time, the low-level operating voltage Vss provided by the fourth power supply terminal is written to the first node N 1 through the third transistor M 3 , the first node N 1 is reset, and the voltage of the electrical signal in the signal reading line RL is also Vss. Then, the third control signal provided by the third control signal line CL 3 is switched to a low level, the third transistor M 3 is turned off, the voltage of the first node N 1 always remains at Vss under the action of the capacitor C, and the voltage of the electrical signal in the signal reading line RL is also Vss.

Because the signal reading line RL has a certain length, a signal transmitted in the signal reading line will be affected by external noise. That is, the signal transmitted in the signal reading line includes not only the signal received from the ultrasonic wave reception circuit but also a noise signal. According to the embodiments of the present disclosure, the external detection component 3 extracts only the part of the signal having the frequency of

1 t 1 + t 2

from the signal transmitted in the signal reading line RL, i.e., accurately identifies the electric signal output by the ultrasonic wave reception circuit 2 in the detection phase P 2 , so as to ensure accurate identification of a valley and a ridge of the fingerprint of the finger according to the extracted electric signal.

According to another embodiment of the present disclosure, referring to FIG. 4 , the ultrasonic wave reception circuit 2 further includes: a sixth transistor M 6 . A control electrode of the sixth transistor M 6 is coupled to a fourth control signal line CL 4 , a first electrode of the sixth transistor M 6 is coupled to a sixth power supply terminal, and a second electrode of the sixth transistor M 6 is coupled to the first electrode of the rectifier diode PN. The sixth power supply terminal is supplied with a low-level operating voltage Vss.

With continued reference to FIG. 5 , the fourth control signal provided by the fourth control signal line CL 4 is at a high level only in the reset phase P 1 , that is, the sixth transistor M 6 is turned on only in the reset phase P 1 . In the reset phase P 1 , the low-level operating voltage Vss supplied by the sixth power supply terminal is written into a second node N 2 to reset the voltage of the second node N 2 , so that the problem that the ultrasonic wave conversion structure 5 or the rectifier diode PN is broken down because of continuous rise of the voltage of the second node N 2 due to multiple charging can be effectively avoided.

Another embodiment of the present disclosure provides a fingerprint identification device including: a fingerprint identification component, which adopts the fingerprint identification component provided in the above embodiments, and the specific contents may refer to the description in the above embodiments, and are not described herein again.

The fingerprint identification device further includes: a detection component 3 coupled to the ultrasonic wave reception circuit through the signal reading line RL; the detection section 3 is configured to extract an electric signal having a frequency f equal to

1 t 1 + t 2

from the signal reading line RL and identify a valley and a ridge of the fingerprint of the finger according to the extracted electric signal.

For example, the detection component 3 may include a filter for extracting a signal having a frequency f equal to

1 t 1 + t 2

from the signal received by the detection component 3 . Alternatively, the detection component 3 may include a processor for executing various data processing algorithms, such as a Fast Fourier Transform (FFT), Singular Value Decomposition (SVD) or wavelet decomposition algorithm, to extract a signal having a frequency f equal to

1 t 1 + t 2

from the signal received by the detection component 3 .

FIG. 6 is a flowchart of a fingerprint identification method provided by an embodiment of the present disclosure, and as shown in FIG. 6 , the fingerprint identification method is based on the fingerprint identification component provided in the above embodiments, and the fingerprint identification method includes steps S 1 to S 3 as follows.

Step S 1 includes: resetting, by the ultrasonic wave reception circuit, an electric signal received by the signal reading line.

Step S 2 includes: transmitting, by the ultrasonic wave transmission circuit, an ultrasonic wave in a direction towards the position of the finger at an interval of a first time period, and receiving the ultrasonic wave reflected by the finger, converting the ultrasonic wave into the electric signal and outputting the electric signal to the signal reading line by the ultrasonic wave reception circuit.

Step S 3 includes: extracting the electric signal from a signal transmitted by the signal reading line and determining texture information of the fingerprint of the finger according to the extracted electric signal by the external detection component.

In a case where the ultrasonic wave transmission circuit includes a first transistor, a second transistor, and an ultrasonic wave generation structure, the detection phase includes output sub-phases and non-output sub-phases which alternate, each output sub-phase has a time duration of t 1 , each non-output sub-phase has a time duration of t 2 , and step S 2 includes:

step S 201 of: in the output sub-phase, turning on the first transistor under the control of the first control signal provided by the first control signal line, turning off the second transistor under the control of the second control signal provided by the second control signal line, and emitting an ultrasonic wave by the ultrasonic wave generation structure; and

step S 202 of, in the non-output sub-phase, turning off the first transistor under the control of the first control signal provided by the first control signal line, turning on the second transistor under the control of the second control signal provided by the second control signal line, and stopping transmission of the ultrasonic wave by the ultrasonic wave generation structure.

For the description of the above steps, reference may be made to the contents in the foregoing embodiments, and details are not repeated herein.

According to the fingerprint identification method provided by the embodiments of the present disclosure, the ultrasonic wave transmission circuit transmits an ultrasonic wave at an interval of the first time period, so that the ultrasonic wave reception circuit receives the ultrasonic wave at an interval of the first time period, and accordingly the electrical signal output by the ultrasonic wave reception circuit 2 has periodicity, that is, the electrical signal has a certain frequency f, which satisfies

f = 1 t 1 + t 2 .

In this case, the external detection component can accurately identify the electrical signal output by the ultrasonic wave reception circuit in the detection phase by only extracting, from the detected electrical signal transmitted in the signal reading line, part of the signal having a frequency of

1 t 1 + t 2 ,

so as to ensure the subsequent accurate identification of a valley and a ridge of the fingerprint of the finger according to the extracted electrical signal.

It could be understood that the above embodiments are merely exemplary embodiments employed to illustrate the principle of the present disclosure, and the present disclosure is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present disclosure, and these changes and modifications are also considered to be within the protection scope of the present disclosure.