CN106406649A - TDR touch screen and touch scanning positioning method - Google Patents

Abstract

The invention discloses a TDR touch screen, which includes a touch area and several parallel and independent U-shaped wires arranged in the touch area, and an insulating layer is arranged above each of the U-shaped wires; it also includes a signal transmitter, a reflector A signal detector and a scanning driving circuit; the input ends of the U-shaped 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 touch screen. The signal transmitter is driven by the scanning drive circuit to sequentially transmit step signals to the input end of each U-shaped wire, 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 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 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 touch screen provided by the present invention includes a touch area and several parallel and independent U-shaped wires distributed in the touch area, and an insulating layer is arranged above each of the U-shaped wires; The TDR touch screen also includes a signal transmitter, a reflected signal detector and a scanning drive circuit; the input end of each of the U-shaped wires is connected to the signal transmitter and the reflected signal detector respectively, and the signal transmitter is connected to the scan driver circuit.

Compared with the prior art, the touch area of the TDR touch screen provided by the present invention is distributed with multiple parallel and independent U-shaped wires, and the input ends of the multiple U-shaped wires are used in turn or share a set of signal transmitters and reflected signal detectors. , The switching of the U-shaped wire is completed by the scanning driving 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 touch screen provided by the present invention can detect multiple impedance change points in a certain time and frequency band, so as 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 snake-shaped wiring, the TDR touch screen provided by the present invention adopts a layout in which multiple U-shaped wires are parallel and independent from each other, and the switching of each U-shaped wire is realized by scanning the driving circuit. Independent signal transmission and signal detection can greatly shorten the length of the wire, thereby reducing the input step signal level and the distributed resistance of the wire, and there is only one angle inflection point in the U-shaped wire, which has little influence on the calculation of the impedance change point, thus Improve positioning accuracy.

Further, in the TDR touch screen, each of the U-shaped wires is a transparent U-shaped wire.

Preferably, in the TDR touch screen, the output end of each U-shaped wire is suspended.

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

Further, each U-shaped wire includes a first wire parallel to each other, a second wire and a third wire connecting the first wire and the second wire; each second wire is connected to the adjacent first wire. The distance between the wires is the same;

Each of the U-shaped wires is distributed in parallel in the first direction of the touch area;

The lengths of the first wire and the second wire of each U-shaped wire are equal to the length of the touch area in the second direction, and the first direction and the second direction are perpendicular to each other.

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

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

When the difference between the reflected signal of any of the U-shaped wires received by the reflected signal detector and the preset reference signal is greater than the preset threshold, the signal transmitter starts to transmit to the U-shaped wire according to the signal. The time delay from the step signal to the 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 U-shaped wires sequentially through the control of the scanning drive circuit to complete the emission and detection of all U-shaped wire signals, thereby realizing the touch function of the entire touch area. The scanning method Simple; and multiple U-shaped wires can share a set of signal transmitters and reflected signal detectors, which has 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 input step on any U-shaped wire The time delay from the signal to the reflected signal of the U-shaped wire received by the reflected signal detector can calculate the position of the impedance change point that causes the reflected signal in the second direction on the U-shaped wire, combined with the U-shaped The preset position of the wire in the first direction locates the touch point, the algorithm is simple, and the difficulty of data processing is low. Compared with the existing touch positioning method using time domain reflection method using serpentine wiring, the touch scanning positioning method provided by the present invention realizes switching of each U-shaped wire to independently perform signal emission and signal detection through the scanning drive circuit, which can greatly shorten the The length of the wire can effectively detect the touch position even when the input step signal level is not high; and the line is straight (only one angle inflection point exists), 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 difference between the reflected signal of any U-shaped wire received by the reflected signal detector and the preset reference signal is determined to be greater than a preset threshold through the following steps:

The load impedance of the reflected signal detector receiving the reflected signal of the U-shaped wire is calculated by the following formula:

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

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

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 U-shaped wire received by the reflected signal detector and a preset reference signal greater than the preset threshold.

Compared with the prior art, the touch scanning positioning method provided by the present invention is determined as a touch point by calculating the position where the difference between the load impedance and the characteristic impedance of the impedance change point that causes the reflected signal on the U-shaped wire is greater than the preset value , so as to 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 U-shaped wire, until the reflected signal detector receives the difference between the U-shaped wire and a preset reference signal greater than a preset threshold The time delay when the signal is reflected, the position of the touch object in the second direction of the touch screen is calculated by the following distance calculation formula:

When D<X ₀ , X=D, Y=Y _r ;

When D>X ₀ , X=2X ₀ -D, Y=Y _c ;

Wherein, T is the time delay, e _r is the dielectric constant, and C is the speed of light transmission; X ₀ is the length of the U-shaped wire in the second direction of the touch screen, and Y _r is the length of the U-shaped wire The position of the input end on the first direction of the touch screen, Y _c is the position of the output end of the U-shaped wire on the first direction of the touch screen, and (X, Y) is the position coordinate of the touch object on the touch screen

Preferably, driving the signal transmitter through the scanning drive circuit to sequentially transmit a step signal to the input end of each U-shaped wire 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 U-shaped wire.

As a preferred solution, the touch scanning method provided by the present invention sequentially scans each U-shaped wire along the first direction of the touch screen from left to right or from right to left, 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, the driving the signal transmitter through the scanning driving circuit to sequentially transmit the step signal to the input end of each U-shaped wire includes:

First drive the signal emitter along the first direction of the touch screen through the scanning drive circuit to transmit step signals to the input end of the U-shaped wire, and then drive the signal emitter along the first direction of the touch screen through the scan drive circuit. Transmitting the step signal alternately in the first direction to the input ends of the remaining U-shaped wires.

As another preferred solution, the touch scanning method provided by the present invention scans the U-shaped wires sequentially from left to right or from right to left along the first direction of the touch screen, and then scans the rest of the U-shaped wires interlacedly (and vice versa). ), so as to obtain the 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 touch screen provided by the present invention.

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

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

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

FIG. 7 is an impedance-time series curve diagram of a U-shaped wire provided on the touch screen without a touch point in a preferred embodiment of the TDR touch screen provided by the present invention.

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

FIG. 9 is an impedance-timing curve diagram when the U-shaped wire provided on the touch screen has a touch point 8B in a preferred embodiment of the TDR touch screen provided by the present invention.

Fig. 10 is a graph showing the waveform of the injected signal provided at the input end of the U-shaped wire of the touch screen according to a preferred embodiment of the TDR 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 touch screen provided by the present invention. The TDR touch screen includes a touch area 1 and several parallel and mutually independent U-shaped wires 2 distributed in the touch area 1 . Each of the U-shaped wires 2 is a transparent U-shaped wire 2 , and the distance between each of the U-shaped wires 2 and the adjacent U-shaped wires is equal.

Specifically, each of the U-shaped wires 2 includes a first wire 201, a second wire 202 parallel to each other, and a third wire 203 connecting the first wire 201 and the second wire 202; each of the second wires 202 is the same as the distance between the adjacent first conductors 201, that is to say, the distance between the first conductors 201 and the second conductors 202 of each U-shaped conductor 2 is the same as that between the adjacent U-shaped conductors 2 are equally spaced.

Each of the U-shaped wires is distributed in parallel in the first direction of the touch area;

The lengths of the first wire and the second wire of each U-shaped wire are equal to the length of the touch area in the second direction, and the first direction and the second direction are perpendicular to each other.

It can be understood that the interval between the first wire 201 and the second wire 202 of each U-shaped wire 2, and the distance between two adjacent parallel U-shaped wires 2 are set according to actual needs. The larger the amount of calculation, the higher the calculation accuracy and the more precise the touch. In the coordinate system constructed on the touch area 1, the first wire 201 and the second wire 202 of each U-shaped wire 2 are set to correspond to the first direction of the touch area 1 (for example, the Y coordinate direction, also referred to as the touch direction). length of the area), and the first wire 201 and the second wire 202 of each U-shaped wire 2 are along the second direction of the touch area 1 (for example, the X coordinate direction, also referred to as the width of the touch area ), the lengths of the first wires 201 and the second wires 202 of each U-shaped wire 2 are equal to the length of the touch area 1 in the second direction (that is, the first wires 201, the second wires 202 The length is consistent with the wide length of the touch area 1). In this embodiment, the length of the third wire 203 is negligible. In this way, by calculating the position where impedance changes occur on each U-shaped wire, the corresponding touch position can be obtained.

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

It can be understood that the TDR touch screen of this embodiment may also not include the substrate 10, but directly coat several parallel and mutually independent U-shaped wires 2 in the form of coating on the display screen and cover the surface of the U-shaped wires 2. The insulating layer 3 is formed later, so that the thickness of the touch screen can be further reduced to meet the requirements of an ultra-thin touch screen.

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

The output end 22 of each U-shaped 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 touch screen provided by the present invention, the output end of each U-shaped 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 touch screen of the present embodiment, when the output terminal 22 of each U-shaped wire 2 is terminated (connected to the load 7) with its characteristic impedance, there is no signal emission, and the output terminal 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 U-shaped wire 2 has a resistance approximately equal to the characteristic impedance of each U-shaped wire 2 .

It can be understood that in this embodiment, the input end 21 of each U-shaped 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 a scanning The driving circuit 6 is driven by the scanning driving circuit 6 to control each signal transmitter 4 to transmit a step signal 101 to the correspondingly connected U-shaped wire 2, and each reflected signal detector 5 receives the reflection of the correspondingly connected U-shaped wire. Signal 102.

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

Referring to Fig. 5, Fig. 5 is an impedance equivalent model diagram of each U-shaped wire 2, and each actual U-shaped wire 2 can be expressed as a cascaded transmission line of each segment equivalent network, which can be equivalent to a distributed resistance R , distributed inductance L, distributed conductance G and distributed capacitance C and other lumped elements composed of a T-shaped network combination. For a lossless U-shaped wire 2, 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 U-shaped 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 U-shaped wire 2 changes, and at this time the U-shaped wire 2 An impedance change occurs at this touch point 8 . The impedance change will cause part of the signal to be reflected back to the input end of the U-shaped wire, and the part of the signal here is called the reflected signal 102 .

Here, the impedance of the U-shaped wire 2 with no load on the output terminal 22 is used as an example to illustrate: as shown in Figure 7, Figure 8 and Figure 9, Figure 7, Figure 8 and Figure 9 are respectively any U-shaped wire 2 without a touch point 1. Impedance-timing curves in the three cases of touch point 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 U-shaped wire 2 , and the curve 113 is the impedance curve of the output terminal 22 suspended. For the contact point 8A and contact point 8B at different positions of the same U-shaped 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. Curve. Different touch positions on the same U-shaped wire 2 lead to different time points on the impedance characteristic curve causing impedance changes.

During specific implementation, the input end 21 of a plurality of parallel U-shaped wires 2 is completed the input of step signal 101 by signal transmitter 4 and the reception of reflected signal 102 is completed by reflected signal detector 5 successively, and the switching of U-shaped wire 2 is controlled by scanning. The drive circuit 6 is completed.

Next, with reference to FIG. 2 and FIG. 10 , the implementation principle and working process of the TDR touch screen of this embodiment will be described in detail. Referring to FIG. 2 , the first direction and the second direction of the TDR 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.

(1) First, preset the position of the input end and the output end of each U-shaped wire 2 in the Y-axis direction, and the input end and the output end of each U-shaped wire 2 are preset in sequence from left to right The positions are Y, Y+1, Y+2...Y+n, and each U-shaped wire 2 extends parallel to the X-axis direction.

(2) The signal transmitter 4 is driven by the scan driving circuit 6 to transmit the step signal 101 to the input end 21 of each U-shaped wire 2 row by row along the Y-axis direction according to a preset cycle. At the same time, the reflection signal 102 corresponding to the input end 21 of each U-shaped 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 U-shaped wire 2 . The injected signal includes a transmitted signal 101 and a reflected signal 102 . The curve represents the relationship between voltage amplitude and timing. It can be known from FIG. 10 that the voltage amplitude of the reflected signal is related to the load impedance of the U-shaped 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 of the U-shaped wire 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 U-shaped wire 2 , and V _r is the amplitude of the reflected signal 102 received by the reflected signal detector 5 from the U-shaped wire 2 .

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

Wherein, Z ₀ is the characteristic impedance of the U-shaped 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. signal 102, it is necessary to locate the position of the touch point 8 in the next step according to the reflected signal 102. Specifically include:

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

When D<X ₀ , X=D, Y=Y _r ;

When D>X ₀ , X=2X ₀ -D, Y=Y _c ;

Wherein, T is the time delay, e _r is the dielectric constant, C is the speed of light transmission, X ₀ is the length of the U-shaped wire on the second direction (X coordinate) of the touch screen, Y _r is the The position of the input end 21 of the U-shaped wire 2 on the first direction (Y coordinate) of the touch screen, _Yc is the position of the output end 22 of the U-shaped wire 2 on the first direction of the touch screen, (X, Y) is the position coordinate of the touch point 8 on the touch screen.

After the position coordinates (X, Y) of the touch point 8 are 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 U-shaped wire 2 row by row, and the corresponding U-shaped wire 2 is detected by the reflected signal detector 5 simultaneously. The reflected signal 102 of the input terminal 21.

When the touch object touches on the touch screen, the impedance of the U-shaped wire 2 where the point of the touch point 8 is located changes; the reflection signal detector 5 receives the reflection signal 102 caused by the touch point 8; by calculating the load of the reflection signal 102 Impedance Z _L , when the difference between the load impedance Z _L and the preset characteristic impedance Z ₀ exceeds the preset value, the position of the touch point 8 is calculated; the step signal 101 is input through the U-shaped wire 2 where the reflected signal 102 is located to The time delay T of detecting the reflected signal 102 calculates the path length between the touch point and the starting point, so as to obtain the coordinate position (X, Y) of the touch point, thereby realizing the touch function of the entire touch screen.

In this embodiment, the scanning method 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 U-shaped 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 each U-shaped wire 2 The input terminal 21 can also be realized by the following scan mode:

The signal transmitter 4 is first driven by the scan drive circuit 6 to transmit the step signal 101 to the input terminal 21 of the U-shaped wire 2 alternately along the Y-axis direction of the touch screen, and then the scan drive circuit 6 is used to drive the The signal transmitter 4 transmits step signals 101 alternately along the Y-axis direction of the touch screen to the input ends 21 of the remaining U-shaped wires 2 . The embodiment of the TDR 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 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 there is only one angle inflection point in the U-shaped wires. The calculation has little influence, thus improving the positioning accuracy. Referring to Figure 11, this embodiment provides a touch scanning positioning method, the touch scanning positioning method

Applicable to the TDR touch screen as described above, the TDR touch screen includes a touch area and several parallel and independent U-shaped wires distributed in the touch area, and an insulating layer is arranged above each of the U-shaped wires; the TDR The touch screen also includes a signal transmitter, a reflected signal detector and a scanning drive circuit; the input end of each of the U-shaped wires is respectively connected to the signal transmitter and the reflected signal detector, and the signal transmitter is connected to the scanning Drive circuit. Wherein, the position of the input end and the output end of each said U-shaped wire in the first direction (for example, the Y coordinate direction) of the touch screen is preset, and each said U-shaped wire is along the second direction (for example, the Y coordinate direction) of the touch screen. , extending parallel to the X coordinate direction). The touch scanning positioning method of the present embodiment includes steps S1 to S2:

S1. Drive the signal transmitter through the scanning drive circuit to sequentially transmit step signals to the input end of each U-shaped wire, and correspondingly receive the signal of each U-shaped wire in sequence through the reflected signal detector The reflected signal at the input;

S2. When the difference between the reflected signal of any one of the U-shaped wires received by the reflected signal detector and the preset reference signal is greater than the preset threshold, the signal transmitter starts to send the signal to the U-shaped wire according to the signal The time delay from the wire transmitting the step signal to this moment (that is, when the reflected signal detector receives the reflected signal whose difference between the U-shaped wire and the preset reference signal is greater than the preset threshold value) is calculated to obtain the touch object The position in the second orientation of the touchscreen.

Wherein, step S1 is used to scan the touch screen (specifically transmit and detect signals to each U-shaped 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 U-shaped 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 row by row along the first direction of the touch screen to the input end of each of the U-shaped wires. Way one scans each U-shaped wire 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.

Method 2: first drive the signal transmitter through the scanning drive circuit to transmit step signals alternately along the first direction of the touch screen to the input end of the U-shaped wire, and then drive the signal transmitter through the scanning drive circuit Transmitting step signals alternately along the first direction of the touch screen to the input ends of the remaining U-shaped wires.

The second way is to scan the U-shaped wires in sequence from left to right or from right to left along the first direction of the touch screen, and then scan the rest of the U-shaped wires (or vice versa), so as to obtain complete scanning data. 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) U-shaped 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 ), and then specifically calculate the specific position of the touch point on the (or multiple) U-shaped wires.

Specifically, in step S2, it is determined that the difference between the reflected signal of any U-shaped wire received by the reflected signal detector and the preset reference signal is greater than a preset threshold through the following steps, referring to FIG. 12, step S2 Concretely include steps S211~S214:

S211. Calculate and obtain the load impedance of the reflected signal received by the U-shaped wire by the reflected signal detector through the following formula (a):

Wherein, Z _L is the load impedance when the reflected signal detector receives the reflected signal of the U-shaped wire, Z ₀ is the characteristic impedance of the preset U-shaped wire, and ρ is the reflection coefficient; wherein, by the following Formula (b) calculates and obtains described reflection coefficient ρ:

Wherein, V _i is the amplitude of the step signal transmitted by the signal transmitter to the U-shaped wire, and V _r is the amplitude of the reflected signal received by the reflected signal detector from the U-shaped 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 U-shaped wire received by the reflected signal detector and the preset reference signal The difference is greater than a preset threshold.

When it is determined that the reflected signal received by any U-shaped wire is the reflected signal generated by the impedance change caused by the normal touch of the touch object, the position of the next touch point needs to be determined according to the reflected signal. Specifically include steps:

S213. According to the signal transmitter starting to transmit a step signal to the U-shaped wire, until the reflected signal detector receives that the difference between the U-shaped wire and the preset reference signal is greater than the preset threshold The time delay when reflecting the signal is calculated by the following distance calculation formula (c) to obtain the path length from the touch point to the input terminal:

Wherein, D is the path length from the touch point to the input end of the U-shaped wire, T is the time delay, e _r is the dielectric constant, and C is the speed of light transmission.

S214. Determine the position coordinate point (X, Y) of the touch point based on the D:

When D<X ₀ , X=D, Y=Y _r ;

When D>X ₀ , X=2X ₀ -D, Y=Y _c ;

Wherein, X ₀ is the length of the U-shaped wire in the second direction of the touch screen, _Yr is the position of the input end of the U-shaped wire in the first direction of the touch screen, and Y _c is the length of the U-shaped wire The position of the output terminal in the first direction of the touch screen, (X, Y) is the position coordinates of the touch object on the touch screen.

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.

The touch scanning positioning method provided in this embodiment switches the U-shaped wires sequentially through the control of the scanning drive circuit to complete the emission and detection of all U-shaped wire signals, thereby realizing the touch function of the entire touch area, and the scanning method is simple; and multiple U-shaped wires U-shaped wires can share a set of signal transmitters and reflected signal detectors, which has low requirements on 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 on any U-shaped wire to the reflected signal The time delay of the reflected signal of the U-shaped wire received by the detector can calculate the position of the impedance change point that causes the reflected signal in the second direction on the U-shaped wire, combined with the preset first position of the U-shaped wire Position the touch point in one direction, the algorithm is simple, and the difficulty of data processing is low. Compared with the existing touch positioning method using time domain reflection method using serpentine wiring, the touch scanning positioning method provided by the present invention realizes switching of each U-shaped wire to independently perform signal emission and signal detection through the scanning drive circuit, which can greatly shorten the The length of the wire can effectively detect the touch position even when the input step signal level is not high; and the line is straight (only one angle inflection point exists), 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 touch screen, characterized in that, the TDR touch screen includes a touch area and several parallel and mutually independent U-shaped wires distributed in the touch area, and an insulating layer is arranged above each of the U-shaped wires; The TDR touch screen also includes a signal transmitter, a reflected signal detector and a scanning drive circuit; the input end of each of the U-shaped wires is respectively connected to the signal transmitter and the reflected signal detector, and the signal transmitter is connected to the The scanning drive circuit described above. 2. The TDR touch screen according to claim 1, wherein each of the U-shaped wires is a transparent U-shaped wire. 3. TDR touch screen according to claim 2, is characterized in that, the output terminal of each described U-shaped wire is suspended in the air; Or, the output terminal of each described U-shaped wire connects one end of load, the other end of described load One end is grounded. 4. The TDR touch screen according to claim 1, wherein each U-shaped wire comprises a first wire parallel to each other, a second wire and a third wire connecting the first wire and the second wire; The distance between each of the second conductive wires and the adjacent first conductive wires is the same; Each of the U-shaped wires is distributed in parallel in the first direction of the touch area; The lengths of the first wire and the second wire of each U-shaped wire are equal to the length of the touch area in the second direction, and the first direction and the second direction are perpendicular to each other. 5. A touch scanning positioning method, characterized in that it is applicable to a TDR touch screen including a touch area and several parallel and mutually independent U-shaped wires distributed in the touch area, wherein each U-shaped wire is preset The position of the input end and the output end of the wire in the first direction of the touch screen, and each of the U-shaped 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 step signals to the input end of each of the U-shaped wires, and the reflection signal detector correspondingly receives the reflected signals of the input ends of each of the U-shaped wires in sequence; When the difference between the reflected signal of any of the U-shaped wires received by the reflected signal detector and the preset reference signal is greater than the preset threshold, the signal transmitter starts to transmit to the U-shaped wire according to the signal. The time delay from the step signal to the moment is calculated to obtain the position of the touch object in the second direction of the touch screen. 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 5, wherein the following steps determine that the difference between the reflected signal of any U-shaped wire received by the reflected signal detector and the preset reference signal is greater than the preset Set the threshold: The load impedance of the reflected signal received by the U-shaped wire by the reflected 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 U-shaped wire, _Z0 is the characteristic impedance of the preset U-shaped wire, and ρ is the reflection coefficient; by the following formula ( b) Calculate the reflection coefficient ρ: Wherein, _V is the amplitude of the step signal transmitted by the signal transmitter to the U-shaped wire, and V is the _amplitude of the reflected signal received by the reflected signal detector of the U-shaped wire; 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 U-shaped wire received by the reflected signal detector and a preset reference signal greater than the preset threshold. 8. The touch scanning positioning method according to claim 5, characterized in that, according to the signal transmitter transmitting a step signal to the U-shaped wire until the reflected signal detector receives the signal of the U-shaped wire and The time delay when the difference of the preset reference signal 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: When D<X ₀ , X=D, Y=Y _r ; When D>X ₀ , X=2X ₀ -D, Y=Y _c ; Wherein, T is the time delay, e _r is the dielectric constant, C is the speed of light transmission, X ₀ is the length of the U-shaped wire in the second direction of the touch screen, Y _r is the length of the U-shaped wire The position of the input end in the first direction of the touch screen, _Yc is the position of the output end of the U-shaped wire in the first direction of the touch screen, (X, Y) is the position coordinate of the touch object on the touch screen. 9. The touch scanning positioning method according to claim 5, wherein driving the signal transmitter through the scanning driving circuit to sequentially transmit a step signal to the input end of each U-shaped wire 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 U-shaped wire. 10. The touch scanning positioning method according to claim 5, wherein driving the signal transmitter through the scanning drive circuit to sequentially transmit a step signal to the input end of each U-shaped wire comprises: First drive the signal emitter along the first direction of the touch screen through the scanning drive circuit to transmit step signals to the input end of the U-shaped wire, and then drive the signal emitter along the first direction of the touch screen through the scan drive circuit. Transmitting the step signal alternately in the first direction to the input ends of the remaining U-shaped wires.