CN106406646A - TDR scanning type touch screen and touch scanning positioning method - Google Patents

Abstract

The invention discloses a TDR scanning touch screen, which includes a touch area and several parallel and independent wires arranged in the touch area, an insulating layer is arranged above the wires; it also includes a signal transmitter, a reflection signal detector and A scanning driving circuit; the input ends of the wires are respectively connected to the signal transmitter and the reflected signal detector, and the signal transmitter is connected to the scanning driving circuit. The present invention also discloses a touch scanning positioning method suitable for the TDR scanning touch screen. The signal transmitter is driven by the scanning drive circuit to sequentially transmit step signals to the input ends of each of the wires, and the The reflection signal detector receives the reflection signal of the input terminal correspondingly in turn; locates the touch position through the time delay between the transmission signal and the input of the step signal. The invention can realize multi-point touch, reduce the difficulty of touch algorithm, and improve the precision of touch positioning.

Description

TDR scanning touch screen and touch scanning positioning method

technical field

The invention relates to the field of touch screens, in particular to a time-domain reflectometry (TDR)-based scanning touch screen and a touch scanning positioning method.

Background technique

Existing touch screens mainly include resistive touch screens, capacitive touch screens, and infrared touch screens.

Resistive touch screens are mainly used in low-end products, usually only have a single touch function. Capacitive touch screens are widely used in various electronic products, but there are problems such as complex manufacturing process and high cost when applied to super-large-sized products, so large-sized products usually use infrared touch screens. Infrared touch screens need to arrange infrared emitting tubes and infrared receiving tubes around the screen, resulting in large volume and thickness, and the accumulation of dust will cause abnormal touch sensing.

In order to solve the above problems, the prior art adopts a touch screen using a time domain reflectometry (TDR) measurement technique. Time Domain Reflectometry (TDR) measurement technology is to input a step signal in the transmission line. If there is an impedance change in the line, part of the signal will be reflected, and the remaining signal will continue to transmit. By measuring the amplitude of the transmitted signal and measuring the amplitude of the reflected signal, the change in impedance can be calculated. At the same time, the position of impedance change can be calculated only by measuring the time difference from the launch to the reflection signal and then to the launch point. When a person's finger is placed on the surface of the transmission line, a capacitance will be formed between the conductor and the insulating layer, which will change the distributed capacitance of the transmission line, and then an impedance change point will be generated. Touching different positions of the transmission line, the impedance curve will also change at different time points.

As shown in Figure 1, the existing touch screen 100 adopting the time domain reflectometry technology is provided with a serpentine transmission line 112 (covering the touch area 114) with a constant impedance on the substrate 110, and the first end of the serpentine transmission line 112 (initial end) connect the first terminating resistor 106, connect the second terminating resistor 104 at the second end (end) of the serpentine transmission line 112 and connect the first terminating resistor 106, the second terminating resistor 104 The mixed signal integrated circuit device 102. The touch position 116, 118 is determined by sending a pulse to the first end (or second end) of the serpentine transmission line 112 and calculating the pulse size and time when the first end (or second end) receives a touch return. Due to the use of a serpentine transmission line, there are problems of excessive length and many inflection points. When implementing it:

1. The signal attenuation reflected at the end of the transmission line is large, requiring a very high input step signal level, resulting in increased radiation; at this time, the distributed resistance of the transmission line cannot be ignored, and additional variable calculation is required;

2. The serpentine transmission line will have multiple large-angle inflection points, and its impedance will also have multiple mutation points, which requires a high algorithm for measuring impedance changes.

Therefore, it is necessary to provide a touch screen that not only can realize multi-touch, has simple manufacturing process, is light and thin, has high quality, but also has simple touch algorithm and high precision.

Contents of the invention

The purpose of the present invention is to provide a TDR scanning touch screen and a touch scanning positioning method, which can realize multi-touch, reduce the difficulty of touch algorithm, and improve the touch positioning accuracy.

In order to achieve the above object, the TDR scanning touch screen provided in one aspect of the present invention includes a touch area and several parallel and independent wires distributed in the touch area, and an insulating layer is arranged above the wires; the TDR scanning touch screen It also includes a signal transmitter, a reflection signal detector and a scanning driving circuit; the input end of each wire is respectively connected to the signal transmitter and the reflection signal detector, and the signal transmitter is connected to the scanning driving circuit.

Compared with the prior art, the touch area of the TDR scanning touch screen provided by the present invention is distributed with multiple parallel and mutually independent wires, and the input ends of the multiple wires are used in turn or share a set of signal transmitters and reflection signal detectors. The switching is completed by the scan drive circuit. The above-mentioned technical solution has a simple manufacturing process and has the advantages of small thickness and light weight, and can be applied to touch control of large-sized liquid crystal screens and ultra-thin products. In addition, the TDR scanning touch screen provided by the present invention can detect a plurality of impedance change points in a certain time frequency range to realize the functions of multi-touch and scanning the shape of the touch object. Compared with the existing touch screen adopting the time domain reflection method using serpentine wiring, the TDR scanning touch screen provided by the present invention adopts a layout in which multiple wires are parallel and independent from each other, and each wire can be switched independently through the scanning drive circuit. Signal transmission and signal detection can greatly shorten the length of the wire, thereby reducing the input step signal level amplitude and the distributed resistance of the wire, and the wire is straight and there is no large-angle inflection point, which is convenient for calculating the impedance change point, thereby improving the positioning accuracy.

Further, in the TDR scanning touch screen, each of the wires is a transparent wire.

Preferably, in the TDR scanning touch screen, the output end of each wire is suspended.

In another preferred embodiment, in the TDR scanning touch screen, the output terminal of each wire is connected to one end of the load, and the other end of the load is grounded.

Another aspect of the present invention provides a touch scanning positioning method, which is suitable for the structure of a TDR scanning touch screen including a touch area and several parallel and mutually independent wires distributed in the touch area. Wherein, the position of each of the wires in the first direction of the touch screen is preset, and each of the wires extends in parallel along the second direction of the touch screen; the method includes the following steps:

The signal transmitter is driven by the scanning drive circuit to sequentially transmit the step signal to the input end of each of the wires, and the reflection signal detector correspondingly receives the reflected signal of the input end of each of the wires in sequence;

When the difference between the reflected signal of any of the wires received by the reflected signal detector and the preset reference signal is greater than a preset threshold, the signal transmitter starts to transmit a step signal to the wire according to the signal transmitter. The time delay at this moment is calculated to obtain the position of the touch object in the second direction of the touch screen.

Compared with the prior art, the touch scanning positioning method provided by the present invention switches the wires sequentially through the control of the scanning drive circuit to complete the emission and detection of all wire signals, thereby realizing the touch function of the entire touch area, and the scanning method is simple; and more The wires can share a set of signal transmitters and reflected signal detectors, which has low requirements on the equipment, which is conducive to the thinning of the touch screen and the reduction of cost; in addition, it only needs to input the step signal to the reflected signal detector by calculating any wire The time delay of the received reflected signal of the wire can calculate the straight-line distance on the wire of the impedance change point that causes the reflected signal, combined with the preset position of the wire to locate the touch point, the algorithm is simple and the difficulty of data processing is low. Compared with the existing touch positioning using serpentine wiring and using time domain reflection method, the touch scanning positioning method provided by the present invention realizes switching of each wire through the scanning drive circuit to perform signal transmission and signal detection independently, which can greatly shorten the length of the wire , Even if the input step signal level is not high, the touch position can still be detected effectively; and the trace is straight, which is convenient for calculating the impedance change point, thereby improving the positioning accuracy.

Further, the first direction and the second direction are perpendicular to each other.

Further, the first direction is the Y-axis direction, and the second direction is the X-axis direction; or, the first direction is the X-axis direction, and the second direction is the Y-axis direction.

Specifically, the following steps are used to determine that the difference between the reflected signal of any wire received by the reflected signal detector and the preset reference signal is greater than a preset threshold:

The load impedance of the reflected signal received by the reflected signal detector from the wire is calculated by the following formula:

Wherein, _ZL is the load impedance when the reflection signal detector receives the reflection signal of the wire, _Z0 is the preset characteristic impedance of the wire, and ρ is the reflection coefficient; the reflection is calculated by the following formula Coefficient ρ:

Wherein, V _i is the amplitude of the step signal transmitted by the signal transmitter to the wire, and V _r is the amplitude of the reflected signal received by the reflected signal detector from the wire.

When the difference between the load impedance _ZL and the characteristic impedance _Z0 is greater than a preset value, it is determined that the difference between the reflected signal of the wire received by the reflected signal detector and a preset reference signal is greater than a preset value set threshold.

Compared with the prior art, the touch scanning positioning method provided by the present invention determines the position as the touch point by calculating the difference between the load impedance and the characteristic impedance of the impedance change point on the wire that causes the reflected signal to be greater than the preset value, thereby Realize the touch function, avoid the interference of abnormal touch, such as abnormal touch caused by dust accumulation, and make the touch more accurate.

Specifically, according to the signal transmitter starting to transmit a step signal to the wire, until the reflected signal detector receives a reflected signal whose difference between the wire and a preset reference signal is greater than a preset threshold The position of the touch object in the second direction of the touch screen is calculated by the following distance calculation formula:

Wherein, D is the position of the touch object in the second direction of the touch screen, T is the time delay, e _r is the dielectric constant, and C is the speed of light transmission.

Preferably, driving the signal transmitter through the scan driving circuit to sequentially transmit step signals to the input ends of each of the wires includes:

The signal transmitter is driven by the scan driving circuit to transmit step signals row by row along the first direction of the touch screen to the input end of each of the wires.

As a preferred solution, the touch scanning method provided by the present invention scans each wire sequentially from left to right or from right to left along the first direction of the touch screen, so as to obtain complete scanning data. The scanning frequency per unit time is high, the response to fast touch is high, and the touch sensitivity is high.

In another preferred embodiment, driving the signal transmitter through the scan driving circuit to sequentially transmit step signals to the input ends of each of the wires includes:

First drive the signal transmitter through the scan drive circuit to transmit step signals row by row along the first direction of the touch screen to the input end of each of the wires located in odd rows; then drive the signal through the scan drive circuit The transmitter transmits step signals row by row along the first direction of the touch screen to the input end of each of the wires located in even rows.

As another preferred solution, the touch scanning method provided by the present invention scans the wires of odd-numbered rows sequentially from left to right or from right to left along the first direction of the touch screen, and then scans the wires of even-numbered rows (and vice versa), In order to obtain complete scan data. The signal processing speed requirement of the entire system is reduced by half, which can save costs.

Description of drawings

FIG. 1 is a schematic structural diagram of a touch screen based on time-domain reflectometry using serpentine wiring provided in the prior art.

FIG. 2 is a schematic structural diagram of a touch screen of a preferred embodiment of the TDR scanning touch screen provided by the present invention.

FIG. 3 is a schematic diagram of a cross-sectional structure of a touch screen in a preferred embodiment of the TDR scanning touch screen provided by the present invention.

Fig. 4 is a circuit connection block diagram of a preferred embodiment of the TDR scanning touch screen provided by the present invention.

FIG. 5 is an equivalent model diagram of wire impedance of a preferred embodiment of the TDR scanning touch screen provided by the present invention.

FIG. 6 is a schematic diagram of a touch object in contact with the touch screen in a preferred embodiment of the TDR scanning touch screen provided by the present invention.

FIG. 7 is an impedance-time-series curve diagram of a non-touch point of a wire provided on the touch screen in a preferred embodiment of the TDR scanning touch screen provided by the present invention.

FIG. 8 is an impedance-timing curve diagram when a wire of a TDR scanning touch screen provided by the present invention has a touch point 8A in a preferred embodiment of the touch screen.

FIG. 9 is an impedance-timing curve diagram of a preferred embodiment of the TDR scanning touch screen provided by the present invention when the wires provided on the touch screen have a touch point 8B.

Fig. 10 is a graph showing the waveform of the injected signal provided at the input end of the wire of the touch screen in a preferred embodiment of the TDR scanning touch screen provided by the present invention.

Fig. 11 is a flow chart of a preferred embodiment of a touch scanning positioning method provided by the present invention.

FIG. 12 is a specific implementation flowchart of step S2 in FIG. 11 .

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Referring to FIG. 2 , FIG. 2 is a schematic structural diagram of a touch screen of a preferred embodiment of a TDR scanning touch screen provided by the present invention. The TDR scanning touch screen includes a touch area 1 and several parallel and mutually independent wires 2 distributed in the touch area 1 . Each of the conducting wires 2 is a transparent conducting wire 2 , and the distance between each of the conducting wires 2 and adjacent conducting wires is equal.

It can be understood that the distance between two adjacent parallel wires 2 is set according to actual needs, the smaller the distance between two adjacent parallel wires 2 , the greater the amount of calculation, the higher the calculation accuracy, and the more accurate the touch. In the coordinate system constructed on the touch area 1, each wire 2 is set to correspond to a coordinate position in the first direction (for example, Y coordinate direction) of the touch area 1, and each said wire 2 is arranged along the touch area 1. The second direction (for example, the X coordinate direction) extends in parallel, so that by calculating the X coordinate of the position where the impedance changes on each wire, the corresponding touch position can be obtained.

Specifically, referring to FIG. 3, FIG. 3 is a schematic cross-sectional structure diagram of the touch screen in this preferred embodiment. The TDR scanning touch screen in this embodiment includes a substrate 10 and several parallel and mutually independent wires arranged on the substrate 10. 2 and an insulating layer 3 covering the wire 2 . Wherein, several parallel and mutually independent wires 2 are distributed on the entire touch area 1 . Wherein, the substrate 10 can be a glass substrate; the wire 2 is made of a transparent and conductive material, such as tin-doped indium oxide (IndiumTinOxide), referred to as ITO; the insulating layer 3 is made of a silicon dioxide film or a PET film. The TDR scanning touch screen of this embodiment is formed by coating several parallel and mutually independent wires 2 on the transparent film (substrate) and then covering the surface of the wires 2 with a silicon dioxide film or a PET film, and then scanning the obtained TDR The type touch screen is placed on the display screen (for example, LCD, LED or OLED, etc.) to adapt to different display screens, so as to be used for various touch operations.

It can be understood that the TDR scanning touch screen of this embodiment may also not include the substrate 10, but directly coat several parallel and mutually independent wires 2 on the display screen in the form of film coating and cover the surface of the wires 2 with an insulating layer. 3 and then formed, which can further reduce the thickness of the touch screen to meet the needs of ultra-thin touch screens.

Referring to FIG. 4, FIG. 4 is a circuit connection block diagram of the touch screen in this embodiment. In this embodiment, the TDR scanning touch screen further includes a signal transmitter 4 , a reflection signal detector 5 and a scanning driving circuit 6 . In conjunction with Fig. 2, wherein, the input end 21 of each wire 2 is respectively connected to the signal transmitter 4 and the reflected signal detector 5, and the signal transmitter 4 is responsible for transmitting the step signal 101 to the input end 21 of the wire 2, and the reflected signal detector 5 It is responsible for receiving the reflected signal 102 of the input end 21 of the line 2 .

The scan drive circuit 6 is connected to the signal transmitter 4 , and the scan drive circuit 6 drives the signal transmitter 4 to sequentially switch the wire 2 to emit a step signal 101 .

The output end 22 of each wire 2 is connected to one end of the load 7, and the other end of the load 7 is grounded. In addition, in actual implementation, based on the structural principle of the TDR scanning touch screen provided by the present invention, the output end of each wire 2 can also be suspended without a load 7, and the above-mentioned improvements are also within the scope of protection of the present invention. Inside. According to the TDR principle, in the TDR scanning touch screen of the present embodiment, when the output end 22 of each wire 2 is terminated (connected to the load 7) with its characteristic impedance, there is no signal emission, and the output end 22 is not terminated. (floating) has a positive signal emission with an amplitude approximately equal to the pulse generated. In this embodiment, the load 7 connected to the output end 22 of each wire 2 has a resistance approximately equal to the characteristic impedance of each wire 2 .

It can be understood that in this embodiment, the input end 21 of each wire 2 can be separately connected (exclusively) to a signal transmitter 4 and a reflected signal detector 5, and each signal transmitter 4 is connected to the scanning drive circuit 6. Each signal transmitter 4 is sequentially driven and controlled by the scanning driving circuit 6 to emit a step signal 101 to the corresponding connected wire 2 , and each reflected signal detector 5 receives the reflected signal 102 of the corresponding connected wire.

In addition, in order to reduce the cost of equipment, the input end 21 of each wire 2 in this embodiment can also be connected (commonly) to a signal transmitter 4 and a reflected signal detector 5, and the scanning drive circuit 6 drives and controls this signal emission. The detector 4 sequentially switches to transmit a step signal 101 to the conductor 2, and the reflection signal detector 5 sequentially receives the reflection signal 102 of the corresponding conductor.

Referring to Fig. 5, Fig. 5 is an impedance equivalent model diagram of each wire 2, and each actual wire 2 can be expressed as a cascaded transmission line of each equivalent network, which can be equivalent to a distributed resistance R and a distributed inductance L A combination of T-shaped networks composed of lumped elements such as distributed conductance G and distributed capacitance C. For a wire 2 without loss, the values of distributed resistance R and distributed conductance G are both zero.

Here we take a T-shaped network as an example to illustrate: the relationship between characteristic impedance Z and distributed resistance R, distributed inductance L, distributed conductance G and distributed capacitance C is expressed as the following two formulas:

Formula 1:

Formula 2:

Among them, U is the voltage applied to both ends of the wire, and I is the current passing through the wire. The characteristic impedance can be derived from the above two formulas For a lossless wire: characteristic impedance

Referring to FIG. 6 , FIG. 6 is a schematic diagram of a touch object in contact with the touch screen. When the touch object touches, the touch object is in contact with the surface of the insulating layer 3, the touch object acts as a conductor, and a capacitance is formed between the conductor and the insulation layer 3, so that the distributed capacitance C of the wire 2 changes, and at this time the wire 2 is at the touch point 8 produces an impedance change. The change in impedance causes a portion of the signal to be reflected back to the input end of the wire, the portion of the signal here being referred to as the reflected signal 102 .

Here, the impedance of the lead wire 2 with no load at the output terminal 22 is taken as an example for illustration: as shown in Figure 7, Figure 8 and Figure 9, Figure 7, Figure 8 and Figure 9 show that any lead wire 2 has no touch point and touch point respectively Impedance-timing curves in three cases of 8A and touch point 8B. Wherein, in FIG. 7 , the curve 111 is the impedance curve of the input terminal 21 , the curve 112 is the impedance curve of the wire 2 , and the curve 113 is the impedance curve of the output terminal 22 suspended. For the contact point 8A and the contact point 8B at different positions of the same wire 2, the curve 114 in FIG. 8 is the impedance change curve caused by the touch point 8A, and the curve 115 in FIG. 9 is the impedance change curve caused by the touch point 8B. . Different touch positions on the same wire 2 lead to different time points on the impedance characteristic curve causing impedance changes.

During specific implementation, the input terminal 21 of a plurality of parallel wires 2 is completed the input of the step signal 101 by the signal transmitter 4 and the reception of the reflected signal 102 by the reflected signal detector 5 in turn, and the switching of the wires 2 is completed by the scanning drive circuit 6 .

Next, with reference to FIG. 2 and FIG. 10 , the implementation principle and working process of the TDR scanning touch screen of this embodiment will be described in detail. Referring to FIG. 2 , the first direction and the second direction of the TDR scanning touch screen used in this embodiment are perpendicular to each other; wherein, the first direction is set as the Y-axis direction, and the second direction is set as the X-axis direction.

First, preset the position of each wire 2 in the Y-axis direction, each wire 2 is preset in sequence from left to right as Y, Y+1, Y+2...Y+n, and every A wire 2 extends parallel to the X-axis direction.

Then, the scan driving circuit 6 drives the signal transmitter 4 to sequentially transmit the step signal 101 row by row along the Y-axis direction to the input terminal 21 of each wire 2 according to a preset cycle. At the same time, the reflection signal 102 corresponding to the input end 21 of each wire 2 is sequentially received by the reflection signal detector 5 .

Referring to FIG. 10 , FIG. 10 is a graph of the injected signal waveform at the input end 21 of the wire 2 , the injected signal includes a transmitted signal 101 and a reflected signal 102 , and the curve represents the relationship between voltage amplitude and timing. It can be seen from FIG. 10 that the voltage amplitude of the reflected signal is related to the load impedance of the wire 2 .

Specifically, the reflection signal detector 5 determines whether the received reflection signal 102 is the reflection signal 102 generated by the impedance change caused by the normal touch of the touch object through the following steps:

First, the reflection coefficient ρ of the reflection signal 102 received by the reflection signal detector 5 from the conductor 2 is calculated by the following formula (b):

Wherein, V _i is the amplitude of the step signal 101 transmitted from the signal transmitter 4 to the wire 2 , and V _r is the amplitude of the reflected signal 102 received by the reflected signal detector 5 from the wire 2 .

Next, the load impedance Z _L of the reflected signal 102 is calculated by the following formula (a):

Among them, Z ₀ is the characteristic impedance of wire 2.

Comparing the calculated load impedance Z _L with the characteristic impedance Z ₀ , when the difference between the load impedance Z _L and the characteristic impedance Z ₀ is greater than the preset value, it is determined that the difference between the reflected signal 102 and the preset reference signal is greater than preset threshold. This step is to determine that the reflected signal 102 is the reflected signal 102 produced by the impedance change caused by the normal touch of the touch object. , it is necessary to locate the next touch point 8 according to the reflected signal 102 . Specifically include:

Obtain the time delay T from the signal transmitter 4 transmitting the step signal 101 to the input end 21 of the wire 2 where the reflected signal 102 is generated to receiving the transmitted signal 102, and calculate the touch point according to the following distance calculation formula (c) The position of 8 in the X-axis direction of the wire 2:

Among them, D is the position of the touch point in the X-axis direction, e _r is the dielectric constant, and C is the speed of light transmission.

The obtained position D is converted into an X coordinate, and combined with the Y coordinate in the Y axis direction of the wire 2 where the reflected signal 102 is located, the position coordinate point (X, Y) of the touch point 8 is determined. The system can make a corresponding touch response according to the position of the touch point 8 .

During specific implementation, under the driving control of the scanning drive circuit 6, the signal transmitter 4 transmits the step signal 101 to the input end 21 of each wire 2 row by row, and the input end 21 of the corresponding wire 2 is detected by the reflected signal detector 5 at the same time The reflected signal 102.

When the touch object is touched on the touch screen, the impedance of the wire 2 at this point of the touch point 8 changes; the reflection signal detector 5 receives the reflection signal 102 caused by the touch point 8; by calculating the load impedance Z _L of the reflection signal 102 , when the difference between the load impedance Z _L and the preset characteristic impedance Z ₀ exceeds the preset value, the position calculation of the touch point 8 is performed; the step signal 101 is input through the wire 2 where the reflection signal 102 is located until the reflection signal is detected The time delay T of 102 calculates the X coordinate, combines with the position of the wire 2 to determine the Y coordinate, and obtains the position of the touch point 8 from the coordinate point (X, Y), thereby realizing the touch function of the entire touch screen.

In this embodiment, the scanning mode adopted by the touch screen is: the scanning driving circuit 6 drives the signal transmitter 4 to transmit the step signal 102 to the input end 21 of each wire 2 row by row along the Y-axis direction.

In addition, on the premise of not departing from the principle of the present invention, in the specific implementation process, the scanning drive circuit 6 in the touch screen provided by the present invention drives the signal transmitter 4 to sequentially transmit the step signal 101 to the input of each wire 2 Terminal 21 can also be realized by the following scanning methods:

First drive the signal transmitter 4 through the scanning drive circuit 6 to transmit the step signal 101 line by line along the Y-axis direction of the touch screen to the input end 21 of each wire 2 located in an odd row; then drive the signal transmitter 4 through the scanning drive circuit 6 along the The Y-axis direction of the touch screen transmits a step signal 101 row by row to the input terminal 21 of each wire 2 located in an even row.

The embodiment of the TDR scanning touch screen provided by the present invention has a simple manufacturing process, has the advantages of small thickness and light weight, and can be applied to touch control of large-sized liquid crystal screens and ultra-thin products. In addition, the TDR scanning touch screen provided by the present invention can detect multiple impedance change points in the same time frequency band to realize the functions of multi-touch and scanning the shape of the touch object. Compared with the existing TDR touch screen with serpentine wires, this embodiment greatly shortens the length of the wires, thereby reducing the input step signal level amplitude and the distributed resistance of the wires, and the wires are straight, which is convenient for calculating the impedance change point.

Referring to FIG. 11 , this embodiment provides a touch scanning positioning method, which is applicable to the TDR scanning touch screen as described above. The TDR scanning touch screen includes a touch area and several touch areas distributed in the touch area. Parallel and mutually independent wires, an insulating layer is arranged above the wires; the TDR scanning touch screen also includes a signal transmitter, a reflected signal detector and a scanning drive circuit; the input end of each wire is respectively connected to the signal An emitter and the reflection signal detector, the signal emitter is connected to the scanning driving circuit. Wherein, the position of each of the wires in the first direction of the touch screen (for example, the Y coordinate direction) is preset, and each of the wires extends in parallel along the second direction of the touch screen (for example, the X coordinate direction). The touch scanning positioning method of this embodiment includes steps S1 to S2:

S1. Driving the signal transmitter through the scanning drive circuit to sequentially transmit step signals to the input end of each of the wires, and correspondingly receive the reflected signal at the input end of each of the wires in sequence through the reflected signal detector ;

S2. When the difference between the reflected signal of any of the wires received by the reflected signal detector and the preset reference signal is greater than a preset threshold, the signal transmitter starts to transmit a step to the wire according to the signal The time delay from the signal to this moment (that is, when the reflection signal detector receives the reflection signal whose difference between the wire and the preset reference signal is greater than the preset threshold value) is calculated to obtain the second direction of the touch object on the touch screen. position on the

Wherein, step S1 is used to scan the touch screen (specifically transmit and detect signals to each wire) to determine whether there is a touch point on the touch screen. Specifically, in step S1, the driving of the signal transmitter through the scanning drive circuit to sequentially transmit step signals to the input ends of each of the wires can be specifically implemented through the following two scanning methods:

Way 1: The signal transmitter is driven by the scan driving circuit to transmit step signals to the input end of each of the wires row by row along the first direction of the touch screen. Way one scans each conductive line sequentially along the first direction of the touch screen from left to right or from right to left, so as to obtain complete scan data. The scanning frequency per unit time is high, the response to fast touch is high, and the touch sensitivity is high.

Mode 2: first drive the signal transmitter through the scan drive circuit to transmit step signals row by row along the first direction of the touch screen to the input end of each of the wires located in odd rows; then drive the signal transmitter through the scan drive circuit The signal transmitter transmits a step signal row by row along the first direction of the touch screen to the input end of each of the wires located in even rows. The second way is to obtain complete scanning data by sequentially scanning odd-numbered wires and then even-numbered wires (or vice versa) along the first direction of the touch screen from left to right or from right to left. The signal processing speed requirement of the entire system is reduced by half, which can save costs.

Step S2 is used to determine the specific position of the touch point on the touch screen. First, determine which (or which) wires the touch point is located on (by detecting whether the difference between the transmitted signal and the preset reference signal is greater than the preset threshold), Then specifically calculate the specific position of the touch point on the (or multiple) wires.

Specifically, in step S2, the following steps are used to determine that the difference between the reflected signal of any wire received by the reflected signal detector and the preset reference signal is greater than the preset threshold value. Referring to FIG. 12, step S2 specifically includes Steps S211-S214:

S211. Obtain the load impedance of the reflected signal received by the reflected signal detector by the following formula (a):

Wherein, _ZL is the load impedance when the reflected signal detector receives the reflected signal of the wire, _Z0 is the preset characteristic impedance of the wire, and ρ is the reflection coefficient; wherein, by the following formula (b) The reflection coefficient ρ is calculated as:

Wherein, V _i is the amplitude of the step signal transmitted by the signal transmitter to the wire, and V _r is the amplitude of the reflected signal received by the reflected signal detector from the wire.

S212. When the difference between the load impedance _ZL and the characteristic impedance _Z0 is greater than a preset value, determine the difference between the reflected signal of the wire received by the reflected signal detector and a preset reference signal greater than the preset threshold.

When it is determined that the reflected signal received by any wire is the reflected signal generated by the impedance change caused by the normal touch of the touch object, it is necessary to determine the position of the touch point in the next step according to the reflected signal. Specifically include steps:

S213, according to the time delay from when the signal transmitter transmits a step signal to the wire to when the reflection signal detector receives a reflection signal whose difference between the wire and a preset reference signal is greater than a preset threshold , the position of the touch object in the second direction of the touch screen is calculated by the following distance calculation formula (c):

Wherein, D is the position of the touch object in the second direction of the touch screen, T is the time delay, e _r is the dielectric constant, and C is the speed of light transmission.

S214. Convert the obtained distance position D into coordinates in the second direction (for example, X coordinate), and combine the coordinates in the first direction (for example, Y coordinate) of the wire where the reflected signal is located, so that the touch point can be determined The location coordinates of the point (X, Y).

In this way, after determining the position of the touch point, the system can make a corresponding touch response according to the position of the touch point.

The specific embodiments of the touch scanning positioning method for improving the scanning mode of the touch screen are also within the protection scope of the present invention.

In the touch scanning positioning method provided in this embodiment, the wires are sequentially switched through the control of the scanning drive circuit to complete the emission and detection of all wire signals, thereby realizing the touch function of the entire touch area, and the scanning method is simple; moreover, multiple wires can share one set The signal transmitter and the reflected signal detector have low requirements on equipment, which is conducive to the thinning of the touch screen and the reduction of cost; in addition, only by calculating the step signal input on any wire to the wire received by the reflected signal detector The time delay of the reflected signal can calculate the straight-line distance of the impedance change point that causes the reflected signal on the wire, combined with the preset position of the wire to locate the touch point, the algorithm is simple and the data processing difficulty is low. Compared with the existing touch positioning using serpentine wiring and using time domain reflection method, the touch scanning positioning method provided by the present invention realizes switching of each wire through the scanning drive circuit to perform signal transmission and signal detection independently, which can greatly shorten the length of the wire , Even if the input step signal level is not high, the touch position can still be detected effectively; and the trace is straight, which is convenient for calculating the impedance change point, thereby improving the positioning accuracy.

The above description is a preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and deformations can also be made, and these improvements and deformations are also considered Be the protection scope of the present invention.

Claims (10)

1. A TDR scanning touch screen, characterized in that, the TDR scanning touch screen includes a touch area and several parallel and mutually independent wires distributed in the touch area, an insulating layer is set above the wires; the TDR The scanning touch screen also includes a signal transmitter, a reflected signal detector and a scanning drive circuit; the input end of each of the wires is respectively connected to the signal transmitter and the reflected signal detector, and the signal transmitter is connected to the scanning Drive circuit. 2. The TDR scanning touch screen according to claim 1, wherein each of the wires is a transparent wire. 3. The TDR scanning touch screen according to claim 2, characterized in that, the output end of each said wire is suspended; or, the output end of each said wire is connected to one end of the load, and the other end of the load is grounded . 4. A touch scanning positioning method, characterized in that it is suitable for a TDR scanning touch screen including a touch area and several parallel and mutually independent wires distributed in the touch area, wherein each wire is preset at The position on the first direction of the touch screen, and each of the wires extends in parallel along the second direction of the touch screen; the method includes the following steps: The signal transmitter is driven by the scanning drive circuit to sequentially transmit the step signal to the input end of each of the wires, and the reflection signal detector correspondingly receives the reflected signal of the input end of each of the wires in sequence; When the difference between the reflected signal of any of the wires received by the reflected signal detector and the preset reference signal is greater than a preset threshold, the signal transmitter starts to transmit a step signal to the wire according to the signal transmitter. The time delay at this moment is calculated to obtain the position of the touch object in the second direction of the touch screen. 5. The positioning method according to claim 4, wherein the first direction and the second direction are perpendicular to each other. 6. The touch scanning positioning method according to claim 5, wherein the first direction is the Y-axis direction, and the second direction is the X-axis direction; or, the first direction is the X-axis direction, The second direction is the Y-axis direction. 7. The touch scanning positioning method according to claim 4, wherein the following steps determine that the difference between the reflected signal of any wire received by the reflected signal detector and the preset reference signal is greater than the preset Threshold: The load impedance of the reflection signal received by the wire by the reflection signal detector is calculated by the following formula (a): Wherein, _ZL is the load impedance when the reflected signal detector receives the reflected signal of the wire, _Z0 is the preset characteristic impedance of the wire, and ρ is the reflection coefficient; calculated by the following formula (b) The reflection coefficient ρ: Wherein, _V is the amplitude of the step signal transmitted by the signal transmitter to the wire, and V is the _amplitude of the reflected signal received by the reflected signal detector from the wire; When the difference between the load impedance _ZL and the characteristic impedance _Z0 is greater than a preset value, it is determined that the difference between the reflected signal of the wire received by the reflected signal detector and a preset reference signal is greater than a preset value set threshold. 8. The touch scanning positioning method according to claim 4, characterized in that, according to the signal transmitter transmitting a step signal to the wire until the reflected signal detector receives the reference of the wire and the preset The time delay when the signal difference is greater than the reflected signal of the preset threshold is calculated by the following formula (c) to obtain the position of the touch object in the second direction of the touch screen: Wherein, D is the position of the touch object in the second direction of the touch screen, T is the time delay, e _r is the dielectric constant, and C is the speed of light transmission. 9. The touch scanning positioning method according to claim 4, wherein driving the signal transmitter through the scanning drive circuit to sequentially transmit step signals to the input ends of each of the wires comprises: The signal transmitter is driven by the scan driving circuit to transmit step signals row by row along the first direction of the touch screen to the input end of each of the wires. 10. The touch scanning positioning method according to claim 4, wherein driving the signal transmitter through the scanning driving circuit to sequentially transmit step signals to the input ends of each of the wires comprises: First drive the signal transmitter through the scan drive circuit to transmit step signals row by row along the first direction of the touch screen to the input end of each of the wires located in odd rows; then drive the signal through the scan drive circuit The transmitter transmits step signals row by row along the first direction of the touch screen to the input end of each of the wires located in even rows.