CN114170639A - Fingerprint identification circuit and method, display panel and display device - Google Patents
Fingerprint identification circuit and method, display panel and display device Download PDFInfo
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- CN114170639A CN114170639A CN202111502583.4A CN202111502583A CN114170639A CN 114170639 A CN114170639 A CN 114170639A CN 202111502583 A CN202111502583 A CN 202111502583A CN 114170639 A CN114170639 A CN 114170639A
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Abstract
The application discloses a fingerprint identification circuit and method, a display panel and a display device, and the fingerprint identification circuit comprises a current reading unit, a photodiode and a current amplification unit, wherein the current amplification unit is used for amplifying current flowing through the current reading unit; the anode of the photodiode is connected to a bias voltage, and the current reading unit is used for reading a current signal flowing through the unit under the control of the first signal line. According to the technical scheme that this application embodiment provided, current signal in order to guarantee that the current reading unit received can be enough big, realize the effective discernment to the light signal of photodiode collection, guarantee the valley ridge signal of effectual differentiation fingerprint, improve fingerprint identification's accuracy, this embodiment increases between current reading unit and photodiode and sets up the current amplification unit, make the photodiode device that adopts thinner I layer can work in external strong light environment and weak light environment and can both satisfy the demand.
Description
Technical Field
The present invention relates to the field of fingerprint identification technologies, and in particular, to a fingerprint identification circuit and method, a display panel, and a display device.
Background
At present, the in-screen fingerprint identification technology combining optical sensing and display mostly adopts a structure of a display back plate and an amorphous Silicon photodiode device, wherein the structure combining an LTPS (Low Temperature polysilicon) process with high mobility and good stability and the amorphous Silicon photodiode device has a great development prospect in the field of mobile phones.
The existing device has good performance in low-brightness environments such as indoor environment and the like, but in high-brightness environments such as outdoor environment in sunny days, the influence of natural light as stray light on a sensor device is huge, the device is easily saturated, the signal difference of fingerprint valley ridges cannot be distinguished, and normal fingerprint identification is interfered, so that a photodiode device structure with low External Quantum Efficiency (EQE) is adopted, the saturation of the photodiode device structure is ensured to be difficult to occur under the irradiation of strong light, and the purpose of distinguishing bright and dark states is achieved.
Currently, the most effective solution for lowering the EQE of a photodiode device is to reduce the I-layer thickness. However, the photodiode device with the layer I with the smaller thickness is used, and in a low-light environment, because the EQE is too low, the generated photocurrent is very small, which causes a reduction in the signal-to-noise ratio, and fingerprint valley and ridge signals cannot be effectively distinguished, so that the accuracy and effectiveness of fingerprint identification are reduced.
Disclosure of Invention
In view of the above-mentioned drawbacks and deficiencies of the prior art, it is desirable to provide a fingerprint identification circuit and method, a display panel, and a display device.
In a first aspect, a fingerprint identification circuit is provided, comprising a current reading unit, a photodiode, and a current amplifying unit, wherein,
the current amplifying unit is arranged between the photodiode and the current reading unit and is used for amplifying the current flowing through the current reading unit;
the anode of the photodiode is connected to a bias voltage,
the current reading unit is used for reading a current signal flowing through the unit under the control of the first signal line.
In a second aspect, there is provided an identification method of a fingerprint identification circuit, which is used for the fingerprint identification circuit, the method includes:
and (3) first state identification: under the control of a second signal line, the third transistor is turned off, and the current reading unit reads a first current which flows through the photodiode;
and (3) second state identification: under the control of a second signal line, the third transistor is turned on, and the current reading unit reads a second current which is the sum of the current flowing through the photodiode and the current flowing through the third transistor.
In a third aspect, a display panel is provided, which includes the fingerprint identification circuit.
In a fourth aspect, a display device is provided, which includes the above display panel.
According to the technical scheme provided by the embodiment of the application, collect optical signals through the photodiode, and convert optical signals into electrical signals, and read the current signal that flows through the current reading unit, carry out the judgement of the optical signals that the photodiode received through this current signal, current signal that in order to guarantee that the current reading unit received can be big enough, realize the effective discernment to the optical signals that the photodiode was gathered, guarantee the effective valley ridge signal who distinguishes the fingerprint, improve fingerprint identification's accuracy, this embodiment increases between current reading unit and photodiode and sets up the current amplification unit, make the photodiode device that adopts thinner I layer can work in the strong light environment of external world and weak light environment and can both satisfy the demand, read by the current reading unit after the current amplification, satisfy fingerprint identification's demand.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:
FIG. 1 is a schematic diagram of a fingerprint identification circuit in this embodiment;
FIG. 2 is a schematic diagram of a fingerprint identification circuit in the present embodiment;
FIG. 3 is a schematic diagram of strong light recognition of the fingerprint recognition circuit in this embodiment;
fig. 4 is a schematic diagram of weak light identification of the fingerprint identification circuit in this embodiment.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
Referring to fig. 1, the present embodiment provides a fingerprint identification circuit, which includes a current reading unit 10, a photodiode 30 and a current amplifying unit 20, wherein,
the current amplifying unit 20 is disposed between the photodiode 30 and the current reading unit 10, and is configured to amplify the current flowing through the current reading unit 10;
the anode of the photodiode 30 is connected to a bias voltage VBias,
the current reading unit 10 is used to read a current signal flowing through the unit under the control of the first signal line Gate 1.
The fingerprint identification circuit provided by the embodiment collects optical signals through the photodiode, and converts the optical signals into electrical signals, and reads the current signals flowing through the current reading unit, the judgment of the optical signals received by the photodiode is carried out through the current signals, the current signals received by the current reading unit can be large enough for ensuring, the effective identification of the optical signals collected by the photodiode is realized, the valley and ridge signals of fingerprints can be effectively distinguished, the accuracy of fingerprint identification is improved, the current amplification unit is additionally arranged between the current reading unit and the photodiode, so that the photodiode device adopting a thin I layer can work in an external strong light environment and a weak light environment and can meet the requirement, the current is read by the current reading unit after being amplified, and the requirement of fingerprint identification is met.
Optionally, the current amplifying unit 20 includes: a first transistor T1, a second transistor T2, and a third transistor T3, wherein,
a source of the first transistor T1 and a source of the second transistor T2 are connected to the current reading unit, a gate of the first transistor T1 is connected to a first pole of the third transistor T3, a gate of the second transistor T2 is connected to a second pole of the third transistor T3, a drain of the first transistor T1 is connected to the negative pole of the photodiode, and a drain of the second transistor T2 is connected to a bias voltage;
the drain of the first transistor T1 is connected to the Gate thereof, and the Gate of the third transistor T3 is connected to the second signal line Gate 2.
As shown in fig. 2, the present embodiment employs a set of current amplifying unit 20 with current amplifying function composed of three transistors to implement the current amplifying function, wherein the source of the first transistor T1 and the source of the second transistor T2 are both connected to the current reading unit, i.e., the first pole of the fourth transistor T4, the drain of the first transistor T1 is connected to the cathode of the photodiode, the anode of the photodiode is connected to the bias voltage, and the drain of the second transistor T2 is also directly connected to the bias voltage; the drain and the gate of the first transistor T1 are connected to ensure that the first transistor T1 operates in a saturation region, and meanwhile, by connecting the gate of the first transistor T1 and the gate of the second transistor T2 to the third transistor T3, when the third transistor T3 is turned on in a low light environment, the first transistor T1 and the second transistor T2 form a cascode structure to ensure that the second transistor T2 also operates in a saturation region.
The current amplifying unit 20 provided in this embodiment performs different modes of operation under different lighting conditions, wherein, in the strong light mode, the third transistor T3 is turned off under the control of the second signal line Gate2, and the current of the current reading unit in the entire fingerprint identification circuit is the current I1 on the path 1, as shown in fig. 3, the current is the photocurrent generated by the photodiode device; when in the low light mode, the third transistor T3 is turned on under the control of the second signal line Gate2, and at this time, the current of the circuit reading unit is the sum I1+ of the currents of path 1 and path 2I2, as shown in fig. 4, the current read by the circuit reading unit is amplified, wherein the first transistor T1 and the second transistor T2 both operate in the saturation region, and the current in path 1 is:
the current in path 2 is:
since the first and second transistors T1 and T2 are cascode structures,
in the above formula, W is the width of the transistor, and L is the length of the transistor; therefore, the circuit structure can copy the current on the channel 1 to the channel 2 in proportion, and further by designing the width and the length of the first transistor T1 and the second transistor T2, the current on the channel 2 can be determined to amplify the current on the channel 1 by a certain time, so that the current in the whole circuit is amplified integrally, an optical signal is improved, and the problem of insufficient signal in a weak light environment can be solved.
The second signal for controlling the third transistor T3 to turn on and off in the above embodiment is determined according to the current ambient light state of the photodiode, wherein the strong light and weak light conditions involved can be determined according to the requirements of the actual fingerprint identification circuit; meanwhile, in the above embodiment, a photodiode device with a thinner I layer is adopted, wherein the thickness of the I layer is generally 2K to 3K nanometers.
Further, the current reading unit is a fourth transistor T4;
the first electrode of the fourth transistor T4 is connected to the source of the first transistor T1 and the source of the second transistor T2, the second electrode of the fourth transistor T4 is connected to a read signal line, and the gate of the fourth transistor T4 is connected to the first signal line.
In the embodiment, the fourth transistor T4 is used as a current reading unit, the second electrode of the fourth transistor T4 is connected to a reading signal line, the current flowing through the fourth transistor T4 is read through the reading signal line, the gate of the fourth transistor T4 is connected to the first signal line, and the on/off of the fourth transistor T4 is controlled under the control of the first signal line, so that the reading of the current signal is realized.
In this embodiment, a current amplification system composed of a set of three transistors is used, and the current amplification unit 20 only extracts photocurrent of the thinned photodiode device under strong light, so that the problem of small corresponding difference of fingerprint valley and ridge signals due to too high EQE can be avoided, and the current of the diode can be amplified in a controllable manner under a weak light environment, so that the requirement of signal-to-noise ratio under weak light is met.
The present embodiment further provides an identification method of a fingerprint identification circuit, which is used for the fingerprint identification circuit, and the method includes:
and (3) first state identification: under the control of a second signal of the second signal line Gate2, the third transistor T3 is turned off, and the current reading unit reads a first current, which is a current flowing through the photodiode;
and (3) second state identification: under the control of a second signal of the second signal line Gate2, the third transistor T3 is turned on, and the current reading unit reads a second current, which is the current flowing through the photodiode plus the current flowing through the third transistor T3.
The present embodiment provides two identification methods for a fingerprint identification circuit, including a first state and a second state, where the first state is a bright light state, the third transistor T3 is turned off, the fingerprint identification circuit forms a current trend as shown in fig. 3, and at this time, the current read by the current reading unit is the current in the path 1; when the second state is a low-light state, the third transistor T3 is turned on, the fingerprint identification circuit forms a current trend as shown in fig. 4, and at this time, the current read by the current reading unit is the current in the path 1 and the path 2, so that the read current signal is amplified in the low-light state, and the amplification factor of the current is controllable, thereby meeting the requirement of the signal-to-noise ratio in the low light.
The embodiment also provides a display panel which comprises the fingerprint identification circuit.
Further, the display device further includes a photo sensor for detecting the light intensity, and controls the third transistor T3 to be turned off by the second signal line when the light intensity is greater than a set value, or controls the third transistor T3 to be turned on by the second signal line when the light intensity is less than or equal to the set value.
In this embodiment, the third transistor T3 is turned on and off according to different light intensities, so that in a low light state, the third transistor T3 is turned on, the read current is amplified, and the effect of the optical signal is improved, preferably, a photosensor is arranged to detect corresponding light intensity, when the detected light intensity is greater than a set value, the third transistor T3 is turned off under the control of the second signal line, and in contrast, the light intensity is detected quantitatively by the photosensor, so that calculation and determination can be performed according to the thickness of the I layer in the actual photodiode and the length and width of the corresponding first transistor T1 and the corresponding second transistor T2, and quantization selection is realized.
The embodiment also provides a display device which comprises the display panel.
It will be understood that any orientation or positional relationship indicated above with respect to the terms "central," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," etc., is based on the orientation or positional relationship shown in the drawings and is for convenience in describing and simplifying the invention, and does not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and is therefore not to be considered limiting; the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may also be oriented 90 degrees or at other orientations and the spatially relative descriptors used herein interpreted accordingly.
The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.
Claims (7)
1. A fingerprint identification circuit is characterized by comprising a current reading unit, a photodiode and a current amplifying unit, wherein,
the current amplifying unit is arranged between the photodiode and the current reading unit and is used for amplifying the current flowing through the current reading unit;
the anode of the photodiode is connected to a bias voltage,
the current reading unit is used for reading a current signal flowing through the unit under the control of the first signal line.
2. The fingerprint recognition circuit of claim 1, wherein the current amplification unit comprises: a first transistor, a second transistor, and a third transistor, wherein,
a source of the first transistor and a source of the second transistor are connected to the current reading unit, a gate of the first transistor is connected to a first pole of the third transistor, a gate of the second transistor is connected to a second pole of the third transistor, a drain of the first transistor is connected to the negative pole of the photodiode, and a drain of the second transistor is connected to a bias voltage;
the drain of the first transistor is connected to the gate, and the gate of the third transistor is connected to the second signal line.
3. The fingerprint recognition circuit of claim 1, wherein the current reading unit is a fourth transistor;
a first pole of the fourth transistor is connected to the source of the first transistor and the source of the second transistor, a second pole of the fourth transistor is connected to a read signal line, and a gate of the fourth transistor is connected to the first signal line.
4. A method of identification of a fingerprint identification circuit for use in a fingerprint identification circuit as claimed in any one of claims 1 to 3, the method comprising:
and (3) first state identification: under the control of a second signal line, the third transistor is turned off, and the current reading unit reads a first current which flows through the photodiode;
and (3) second state identification: under the control of a second signal line, the third transistor is turned on, and the current reading unit reads a second current which is the sum of the current flowing through the photodiode and the current flowing through the third transistor.
5. A display panel comprising a fingerprint recognition circuit according to any one of claims 1 to 3.
6. The display panel according to claim 5, further comprising a photosensor for detecting light intensity and controlling the third transistor to be turned off by the second signal line when the light intensity is greater than a set value, or controlling the third transistor to be turned on by the second signal line when the light intensity is equal to or less than the set value.
7. A display device characterized by comprising the display panel according to claim 5 or 6.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116704559A (en) * | 2023-07-28 | 2023-09-05 | 南京大学 | Quantum fingerprint identification method and system based on asynchronous two-photon interference |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116704559A (en) * | 2023-07-28 | 2023-09-05 | 南京大学 | Quantum fingerprint identification method and system based on asynchronous two-photon interference |
| CN116704559B (en) * | 2023-07-28 | 2023-11-03 | 南京大学 | Quantum fingerprint identification method and system based on asynchronous two-photon interference |
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