CN106295540A - Use single device to realize display to drive and the method for fingerprint image acquisition - Google Patents

Abstract

The method for display driving and fingerprint image collection provided by the present invention can realize display driving and fingerprint image collection by using a single device, thus simplifying the production and assembly process of the display screen compared with the prior art.

Description

Method for Realizing Display Driving and Fingerprint Image Acquisition Using Single Device

technical field

The invention relates to the field of display screen fingerprint recognition, and more specifically, relates to a method for realizing display driving and fingerprint image collection by using a single device.

Background technique

With the popularization of digital products, especially smart phones and tablet computers, human-computer interaction interface technology represented by touch screens has been widely used. At present, among the unlocking methods of smart terminals, the combination password of "number + letter", sliding screen unlocking and pattern unlocking are the most commonly used. In recent years, smart phones have added a special function—fingerprint recognition and unlocking, such as the Atrix4G released by Motorola in 2011, adding new applications to the field of fingerprint recognition. By October 2013, Apple launched the iPhone 5S with fingerprint recognition function, which was favored by the market, making the application of human-machine interface interaction technology enter a new milestone.

Commonly used fingerprint collection sensors on the market include photoelectric, capacitive, radio frequency and thermal conductivity. Among them, the principle of photoelectric fingerprint collection sensor to collect fingerprints is as follows: when a finger touches the display screen, the finger reflects the light from the backlight through the liquid crystal to the surface of the display screen back to the LCD backplane, and the photoelectric fingerprint collection sensor reflects back to the LCD backplane The light is collected and the collected images are sent to the fingerprint recognition system, which then performs fingerprint imaging recognition. At present, discrete devices are used for driving the touch screen and collecting fingerprint images, and the production and assembly process is complicated, the cost is high, and the power consumption is high.

Contents of the invention

In order to solve at least one defect of the above prior art, the present invention provides a method for realizing display driving and fingerprint image collection. The method can realize display driving and fingerprint image collection by using a single device, thus enabling the production of touch screens The assembly process is simplified compared to the prior art.

For realizing above-mentioned purpose of the invention, the technical scheme that adopts is:

A method for realizing display drive and fingerprint image collection by using a single device is to use a double-gate photoelectric thin film transistor for display drive and fingerprint image collection, the source of the double-gate photoelectric thin film transistor is connected to one end of the capacitor C _LC , and the capacitor C The other end of the _LC is called a common electrode. The double-gate photoelectric thin film transistor includes two operating modes, which are display drive mode and fingerprint image acquisition mode, respectively as follows:

(1) Display drive mode

When the touch-activated switch detects no touch action, the double-gate photoelectric thin film transistor works in a display driving mode, which includes the following steps:

a) Writing phase: set the dark gate of the double-gate photoelectric thin film transistor to a positive voltage, and if the last state of the double-gate photoelectric thin film transistor is in a negative polarity driving state, apply a voltage to the drain of the double-gate photoelectric thin film transistor. Positive bias voltage, and charge the light gate and source of the double-gate photoelectric thin film transistor from negative voltage to positive voltage, and apply a negative voltage to the common electrode; if the last state of the double-gate photoelectric thin film transistor is in the positive polarity driving state, Then apply a negative bias voltage to the drain of the double-gate photoelectric thin film transistor, and discharge the light gate and source of the double-gate photoelectric thin film transistor from positive voltage to negative voltage, and apply a positive voltage to the common electrode;

At this time, the display signal is sent to the display unit through the drain and source of the double-gate photoelectric thin film transistor, and the display signal drives the display unit;

b) Holding stage: after the writing operation is completed, a negative bias voltage is applied to the dark gate of the double-gate photoelectric thin film transistor, and the voltages of the photo-gate, source and common electrode remain unchanged;

c) Modulation stage: after the hold stage lasts for a certain period of time, it enters the modulation stage. In the modulation stage, the common electrode voltage is increased or decreased to prepare for the drive of the next state of the display unit, and to make the double gate photoelectric thin film transistor dark gate The bias voltage of the electrode and the drain remains unchanged;

(2) Fingerprint image acquisition mode

When the touch start switch detects a touch action, the touch start switch is closed, and the double-gate photoelectric thin film transistor works in the fingerprint image acquisition mode. This mode includes the following steps:

d) Reset stage: the dark gate of the double-gate photoelectric thin film transistor is set to a negative voltage, and the photo-gate, source, drain and common electrode are set to a positive bias, and the photo-gate is reset;

e) Collecting stage: After reset is completed, the dark gate, drain, light gate and source of the double-gate photoelectric thin film transistor are set to negative bias voltage, the double-gate photoelectric thin film transistor is completely turned off, and the common electrode is kept positive Bias voltage, the light reflected from the finger is absorbed by the photo-gate, which stimulates the generation of photo-generated carriers and is stored in the photo-gate;

f) Reading stage: after the collection stage is completed, apply positive bias voltage to the dark gate and drain of the double-gate photoelectric thin film transistor, and apply negative bias voltage to the common electrode, photogate, and source, so that the data stored in the photogate The photogenerated carriers can be output through the source of the double-gate photoelectric thin film transistor.

As a preferred solution, the Touch-initiated Switch end of the touch-initiated switch is connected to the light gate of the double-gate photoelectric thin film transistor, and the touch-initiated switch controls the voltage applied to the light gate through the Touch-initiated Switch end.

Compared with prior art, the beneficial effect of the present invention is:

(1) The display unit can be driven by a single device, and the fingerprint image collection can be realized, the generation and assembly process is simple, and the complexity is reduced;

(2) A common electrode is added, and the voltage of the display signal output by the double-gate photoelectric thin film transistor is adjusted by means of common electrode voltage modulation, so that the voltage of the display signal input to the double-gate photoelectric thin film transistor can be appropriately reduced, thereby Reduce the power consumption of the driver IC that forms the display signal output to the double-gate photoelectric thin film transistor, and effectively increase the aperture ratio and light transmittance;

3) The collected fingerprint image has high signal-to-noise ratio and high resolution.

Description of drawings

FIG. 1 is a schematic diagram of ports of a double-gate photoelectric thin film transistor.

Fig. 2 is a principle process diagram of common electrode voltage modulation.

Fig. 3 is a driving timing diagram of the light gate, the dark gate, the source, the drain and the common electrode in the display driving mode.

Fig. 4 is a timing diagram of the acquisition of the light gate, the dark gate, the source, the drain and the common electrode in the fingerprint image acquisition mode.

detailed description

The accompanying drawings are for illustrative purposes only and cannot be construed as limiting the patent;

The present invention will be further elaborated below in conjunction with the accompanying drawings and embodiments.

Example 1

The double-gate photoelectric thin film transistor is a four-terminal device, as shown in Figure 1, which consists of a photo gate (Photo Gate-PG), a dark gate (Dark Gate-DG), a source (S) and a drain (D) composition. The double-gate photoelectric thin film transistor can be regarded as two TFTs placed in parallel back to back. The top TFT is composed of a light gate, source, and drain, and the bottom TFT is composed of a dark gate, source, and drain. In the present invention, the light gate, dark gate, source, and drain of the double-gate photoelectric thin film transistor are successively represented as a reset line (Reset), a selection line (Select), a bias line (Bias) and a data line (Data) .

In the method provided by the present invention, the dual-gate photoelectric thin film transistor has two working modes, which are display driving mode and fingerprint image acquisition mode respectively, and the specific scheme is as follows:

1. Display drive mode

When the touch start switch detects no touch action, the double-gate photoelectric thin film transistor is in the display driving mode, the data line (Data) is switched to the "Display" end, the bottom TFT is used as a switch for the display signal, and the reset line and the data line are connected to each other. The capacitor can be used as a storage capacitor to improve the capacitance leakage of the double gate photoelectric thin film transistor.

Due to the DC blocking effect of the alignment film, the mobile ion and DC residual effect, and the avoidance of liquid crystal flickering, it is necessary to use "polarity inversion" display signals to drive the display unit in the prior art. In this embodiment, in order to reduce the power consumption of the driving IC that forms the display signal output, the source of the double-gate photoelectric thin film transistor is deliberately connected to one end of the capacitor C _LC , and the other end of the capacitor C _LC is called a common electrode. The common electrode adjusts the voltage of the display signal output by the double-gate photoelectric thin film transistor through the modulation of the common electrode voltage, so that the voltage of the display signal input to the double-gate photoelectric thin film transistor can be appropriately reduced, thereby reducing the display signal. The power consumption of the driver IC output to the dual-gate photo-thin film transistor.

The principle of common electrode voltage modulation is shown in Figure 2. The common electrode voltage modulation includes three working stages, which are write stage, hold stage and common electrode modulation stage. For example, as shown in ①, ②, and ③ of Figure 2, the bottom TFT of the double-gate photoelectric thin film transistor is turned on during the writing phase, the drain inputs 4V voltage, the source outputs 4V voltage, and the common electrode inputs 0V voltage; and In the holding phase, the bottom TFT of the double-gate photoelectric thin film transistor is disconnected. At this time, the drain maintains a bias input, the source maintains a 4V voltage, and the common electrode inputs a 0V voltage; while in the common electrode modulation phase, the double gate The TFT at the bottom of the photoelectric thin film transistor is disconnected, and the common electrode is input with 5V voltage. At this time, the source maintains the original voltage difference with the common electrode, and its voltage will be adjusted to 9V. For another example, as shown in ④, ⑤, and ⑥ of Figure 2, the bottom TFT of the double-gate photoelectric thin film transistor is turned on during the writing phase, the drain inputs 1V, the source outputs 1V, and the common electrode inputs 5V; and In the holding phase, the bottom TFT of the double-gate photoelectric thin film transistor is disconnected. At this time, the drain maintains a bias input, the source maintains a voltage of 1V, and the common electrode inputs a 5V voltage; while in the common electrode modulation phase, the double gate The TFT at the bottom of the photoelectric thin film transistor is disconnected, and the common electrode is input with 0V voltage. At this time, the source maintains the original voltage difference with the common electrode, and its voltage will be adjusted to -4V.

The display driving mode includes three stages in the specific process, as shown in Figure 3, which are the writing stage, the holding stage and the modulation stage, and the specific content of each stage is as follows:

a) Write stage T _write

When the last state of the double-gate photoelectric thin film transistor is driven by negative polarity, the double-gate photoelectric thin film transistor enters the T _charge state, the selection line (Select) is set at a positive voltage to make the bottom TFT in the open current state, and the data line (Data) is applied Positive bias voltage, the reset terminal (Reset) and the bias line (Bias) are charged from negative voltage to positive voltage, and the common electrode (Com) applies a negative voltage.

When the previous state of the double-gate photoelectric thin film transistor is driven with positive polarity, the double-gate photoelectric thin film transistor enters the T _discharge state, the selection line (Select) of the bottom TFT is still set at a positive voltage, and the data line (Data) is negatively biased. voltage, the reset terminal (Reset) and the bias line (Bias) are discharged from positive voltage to negative voltage, and the common electrode (Com) applies positive voltage;

b) Hold stage T _Hold

When the double-gate photoelectric thin film transistor is in the T _charge state or T _discharge state, after the writing operation T _write is completed, it enters the T _Hold stage. At this time, the selection line (Select) applies a negative bias voltage, and the reset terminal (Reset), the bias line (Bias), common electrode (Com) voltage remains unchanged, consistent with the state when T _write is completed. The storage capacitor between the light gate and the dark gate can slow down the leakage of the capacitance of the double-gate photoelectric thin film transistor.

c) Modulation stage T _Modulate

When the double-gate photoelectric thin film transistor is in the T _charge state, after the write operation T _write stage and the hold T _Hold stage are completed, enter the modulation T _Modulate stage, increase the common electrode (Com) voltage to prepare for the next stage of driving, and select the line (Select) maintains a negative bias, and the data line (Data) and bias line (Bias) maintain a positive bias.

When the double-gate photoelectric thin film transistor is in the T _discharge state, after the write operation T _write stage and the hold T _Hold stage are completed, enter the modulation T _Modulate stage, reduce the common electrode (Com) voltage to prepare for the next stage of driving, and select the line (Select) maintains a negative bias, and the data line (Data) and bias line (Bias) maintain a negative bias.

2. Fingerprint image acquisition mode

When the touch start switch detects a touch action, the touch start switch is closed, the double gate photoelectric thin film transistor works in the fingerprint image acquisition mode, the data line (Data) is switched to the "Imaging" end, the bottom TFT is still used as a switch, and the top TFT The role is to collect and store photoelectrons. As shown in Figure 4, the operation of this mode is divided into three stages in turn:

d) Reset stage T _Reset : the selection line (Select) is set at a negative voltage so that the bottom TFT is in a current-off state, and the reset line (Reset) and the bias line (Bias), the data line (Data), and the common electrode (Com) are applied positive The bias voltage resets the photogate in preparation for the collection of photoexcited free electrons.

e) Collection stage T _Integration : Immediately after the reset operation, the selection line (Select), data line (Data), reset line (Reset), and bias line (Bias) are set to negative bias to make the double-gate photoelectric thin film transistor completely closure. The common electrode (Com) maintains a positive bias, and the light reflected from the finger passes through the photo-gate and is absorbed by the top TFT to generate electron-hole pairs, which are temporarily stored in the top TFT.

f) Reading stage T _Read : When the collection of photoelectrons is completed, a positive bias is applied to the select line (Select), and the bottom TFT is quickly opened to allow current to flow into the charge amplifier. At the same time, the data line (Data) applies a positive bias voltage, and the common electrode (Com), reset line (Reset) and bias line (Bias) apply a negative bias voltage to transfer photo-generated carriers to the bottom TFT for conduction.

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (2)

1. use single device to realize display to drive and a method for fingerprint image acquisition, be to use bigrid optoelectronic film Transistor carries out display and drives and fingerprint image acquisition, it is characterised in that: the source electrode of bigrid photo tft and electric capacity C_LCOne end connect, electric capacity C_LCThe other end be referred to as common electrode, described bigrid photo tft includes two works Operation mode, is respectively display drive pattern and fingerprint image acquisition pattern, concrete as follows:

(1) display drive pattern

When touching activate switch and can't detect touch action, bigrid photo tft is operated in display drive pattern, It comprises the following steps:

A) write phase: make the dark grid of bigrid photo tft be set to positive voltage, if bigrid optoelectronic film is brilliant Body pipe Last status is in negative polarity driving condition, then apply positive bias to the drain electrode of bigrid photo tft, and Make the photogate of bigrid photo tft, source electrode be charged to positive voltage by negative voltage, and apply negative voltage to common electrode； If bigrid photo tft Last status is in positive polarity driving condition, then to bigrid photo tft Drain electrode applies back bias voltage, and makes the photogate of bigrid photo tft, source electrode are discharged to negative voltage by positive voltage, and to Common electrode applies positive voltage；

Now show that signal is delivered to display unit by the drain electrode of bigrid photo tft, source electrode, show signal pair Display unit is driven；

B) keep the stage: after completing write operation, apply back bias voltage to the dark grid of bigrid photo tft, and make light Grid, source electrode, the voltage of common electrode keep constant；

C) the modulation stage: entering the modulation stage after keeping stage certain time, common electrode voltage is carried by the modulation stage High or reduce, the driving for display unit NextState is prepared, and makes the dark grid of bigrid photo tft, drain electrode Bias keeps constant；

(2) fingerprint image acquisition pattern

When touching activate switch and touch action being detected, bigrid photo tft is operated in fingerprint image acquisition mould Formula, this pattern comprises the following steps:

D) reseting stage: the dark grid of bigrid photo tft is set to negative voltage, photogate, source electrode, drains and is total to Electrode is set to positive bias, resets photogate；

E) collection phase: after completing to reset, make dark grid, drain electrode, photogate and the source electrode of bigrid photo tft set Being set to back bias voltage, bigrid photo tft completely closes, and makes common electrode keep positive bias, comes in from finger reflection Light is absorbed by photogate, excites the generation of photo-generated carrier and is saved in photogate；

F) read the stage: after completing collection phase, apply positive bias to the dark grid of bigrid photo tft, drain electrode, And applying back bias voltage to common electrode, photogate, source electrode so that the photo-generated carrier being saved in photogate can pass through double grid aurora The source electrode output of thin film transistor.

The single device of employing the most according to claim 1 realizes display and drives and the method for fingerprint image acquisition, its feature It is: the Touch-initiated Switch end of described touch activate switch and the photogate of bigrid photo tft Connect, touch activate switch and control to apply the voltage to photogate by Touch-initiated Switch end, thus real Now utilize touch-control to activate fingerprint collecting, effectively reduce power consumption.