CN202058120U - Touch control system of touch screen - Google Patents

Abstract

The utility model provides a control system of a touch screen, which comprises a touch screen, a touching induction circuit, a sampling hold circuit, a multiplexer, an analog-to-digital converter and a controller. An output signal of the touch screen is inducted by a charge induction circuit and is output and buffered into the sampling hold circuit, the sampling treatment of the signal is carried out by the sampling hold circuit, the stored signal is sequentially supplied to the ADC converter by the analog multiplexer, and a digital output after being converted is transmitted to the micro control unit (MCU) controller for digital treatment.

Description

The touch-control system of touch-screen

Technical field

The utility model relates to the touch technology field, and more specifically, the utility model relates to a kind of touch-screen and touch-control system thereof.

Background technology

Projecting type capacitor formula touch-screen is the technology of Apple in issue in 2007, and its mobile cellular telephone iPhone is the commercial Application of first employing projecting type capacitor formula touch panel.By permanance, reliability and the overall performance of further raising projecting type capacitor formula touch panel, projecting type capacitor formula touch panel is accelerated the growth of touch panel industry just day by day.

Projecting type capacitor formula touch technology comprises self-capacitance and mutual capacitance.Wherein, self-capacitance is also referred to as absolute capacitance or stray capacitance, and from engineering viewpoint, self-capacitance is considered to connect the stray capacitance of object and the earth.Most of self-capacitance sensors are brought into play function by the variation of the capacity of detection self-capacitance, and capacitive transducer has the induction electrode that conductive materials is made usually, by sending the electric capacity that electric charge in a small amount comes exploring electrode internally.When the mankind touched the body proximity transducer, the electric capacity of human body touch body and the coupling capacitance of sensing electrode can change the self-capacitance of sensing electrode.The comparison of self-capacitance by sensing electrode and original self-capacitance can determine whether touch panel has the human body contact.

Fig. 1 illustrates the distribution of electrodes and the structure of a kind of self-capacitance touch panel of prior art.The glass substrate top is transparent sensing electrode, and these electrodes are in the same plane and isolated each other.Each electrode has a tail to link to each other with the sensor of self-capacitance.The quantity of inductor chip is directly proportional with the quantity of contact point.In touch panel applications, owing to the cost height of directly responding to, so it is not used usually.

Mutual capacitance is also referred to as conduction electric capacity, and the mutual capacitance touch panel moves based on the coupling capacitance between their electrodes of induction or the variation of mutual capacitance.As shown in Figure 2, the electrode of mutual capacitance touch panel is made up of driver circuit and induction line.These lines are in two mutually perpendicular separation layers, and are mingled with megohmite insulant between this is two-layer.In the normal running, activate drive wire, between adjacent electrode, set up capacitive coupling.When sense object touches when an electrode projects the field line of another electrode, can detect variation and definite contacting points position of mutual capacitance.The mutual capacitance touch panel has good optical outward appearance and sensing stability, but the manufacturing cost height of existing implementation method, complex process.

For other touch panel of the prior art, there is the problem of optical clarity and permanance in the resistive touch panel technology, and there is inhomogeneity problem in surface capacitance touch screen technology, and SAW and IR technology are difficult to be applied to portable set.Though the projected capacitive contact panel is better than other effect, touch-screen is formed with multilayer, and peripheral circuit is many, manufacturing cost height, complicated technology realization.

The utility model content

For overcoming the above-mentioned a plurality of defectives in the existing touch screen technology, the utility model proposes a kind of touch-screen and touch-control system thereof.

According to an aspect of the present utility model, a kind of touch screen control system has been proposed, comprise touch-screen, touch induction circuit, sample-and-hold circuit, Port Multiplier, analog to digital converter and controller, the output signal of described touch-screen is through the electric charge induction circuit inductance, output is buffered in the sample-and-hold circuit, sample-and-hold circuit is to the processing of taking a sample of this signal, by the simulation Port Multiplier signal that stores is supplied to the ADC converter successively, numeral output after the conversion is sent to the MCU controller and carries out digital processing, described touch induction circuit comprises drive point and induction point, connect mutual capacitance between the two, drive point and induction point pass through self-capacitance ground connection separately respectively, induction point is connected to the electric charge induction circuit by resistor, drive point resistors in series and galvanometer, galvanometric other end ground connection.

Described electric charge induction circuit comprises charge amplifier, charge amplifier feedback condenser in parallel.

Described each induction point all is connected with a charge amplifier.

Description of drawings

Fig. 1 is the self-capacitance touch panel structural representation of prior art;

Fig. 2 is the mutual capacitance touch panel structural representation of prior art;

Fig. 3 is the structural representation according to the touch panel of the utility model embodiment;

Fig. 4 is the electrode synoptic diagram according to the direct driving of the utility model embodiment;

Fig. 5 is the measurement result figure of the corresponding electric capacity of sensor of different size;

Fig. 6 is the distribution of electrodes figure according to the multiple spot design of the utility model embodiment;

Fig. 7 is the 3D synoptic diagram according to the touch-sensitive area unit of the utility model embodiment;

Fig. 8 is according to the touch sensing unit of the utility model embodiment structural drawing when the no finger touch;

Fig. 9 is the sensing unit synoptic diagram according to the utility model embodiment shunt mode when the finger touch;

Figure 10 is the sensing unit synoptic diagram of transmission mode when finger closely touches;

Figure 11 is the circuit diagram of charge amplifier;

Figure 12 is the structured flowchart according to the touch control system of the utility model embodiment;

Figure 13 is the result schematic diagram of finger touch diverse location;

Figure 14 is the result schematic diagram that finger touches under different pressures;

Figure 15 is the synoptic diagram of catching of multiple point touching detection.

Embodiment

Below in conjunction with the drawings and specific embodiments a kind of touch-screen and the control system thereof that the utility model provides is described in detail.

(Indium Tim Oxide, ITO) form, and realizes complexity and cost height by electrode by two-layer tin indium oxide for traditional mutual capacitance touch panel.The present invention discloses a kind of method of making multiple spot individual layer touch panel, and touch panel only is made up of a transparent ITO electrode thin layer that is deposited on the glass substrate.

Fig. 3 is the structural representation according to the touch-screen of the embodiment of the invention.As shown in Figure 3, touch-screen comprises touch panel and LCD unit.Touch panel is positioned at the top of LCD unit, and touch panel only is made up of one deck ITO electrode that is deposited on the glass substrate.For the application of touch-screen, touch panel can be laminated on the LCD unit.The ITO electrode down, between glass substrate and LCD unit.Glass substrate can provide protection for touch panel, is not subjected to scratch, and improves the durability of design.The ITO Butut adopts the photoetching of standard.In the practice, can add bonding coat and screen layer.

1), in glass substrate (for example, thickness is 1.1mm) in further detail, wherein, as shown in Figure 3, touch panel manufacturing process comprises:, wherein one side apply ITO layer (for example, thickness is 1500 dusts); 2), be that photolithography seal (photolithography) prepares the pattern of electrode, the minimum spacing between the electrode is 100um; 3), in photolithography seal (photolithography) mode, the ITO layer of glass sheet is made the apperance of electrode.Between the glass substrate of touch panel and LCD unit, arrange polarizer.

ITO electrode layer of the present invention adopts mutual capacitance, comprises the drive wire and the line of induction.For the application as keyboard or controller equiment, the touch area is clear and definite for the technician, and it can adopt direct driving.As shown in Figure 4, the inductor of ITO electrode layer comprises drive electrode and induction electrode, and wherein, in the middle of induction electrode was positioned at, drive electrode was around induction electrode.

Usually, the size of electrode can influence capacity coupled result, determines preferred size by the capacitance variations of test different size touch inductor under finger touch.The mutual capacitance of using HP4284A (the accurate LCR table of Hewlett-Packard/Agilent 4284A is measured the electric capacity between the two poles of the earth) to measure the different size between drive electrode and the induction electrode.As Fig. 5, the capacitance variations corresponding to different external areas is shown, it is 2x2 that external area is shown respectively among the figure, 4x4,6x6 and 8x8 (mm ²) measurement result of pairing capacitance variations.

When the finger proximity transducer, capacitance can descend, and this electric capacity drop-out value is directly proportional with the electric field amount of being shunted.When the size of sensor strengthened, mutual capacitance also increased thereupon.But effectively the electric capacity drop-out value reaches capacity because of the approaching of finger, and shows downward trend.This is because the contact area between finger and the touch panel no longer is enough to contain the whole circumference of sensor.Therefore, if the size of sensor is too little, then can cause the coupling capacitance difference that can not offer the best to respond touch action.Consider this two factors, the size of mutual capacitance sensors should be best suited in this scope of 4-6mm.

Fig. 6 illustrates the entire I TO distribution of electrodes of multiple point touching panel, and right-hand component view and left side general view are not corresponding among Fig. 6, and the oblique line on the right is filled the only below of on the left side, and it is not even distribution.Shown in the little figure in right side, a left side tiltedly is to drive, and the right side tiltedly is induction, and what fill grid is pad, and the touch-sensitive area unit is exaggerated demonstration in this drawing.In each touch sensing unit, in the middle of an induction zone is mixed in by 2 drive areas.Each drive area has an independent lead-in wire to be connected with outside.In Fig. 6, there are some drive areas to be provided with highlighted demonstration, they have represented one of 8 levels virtual " drive wire " on the panel, and the outside links together.Therefore, a line of induction and 8 that has 8 cylindricalitys is listed as virtual drive wire.

About the Multipoint Drive method, at first use first row of virtual drive wire, and other untapped drive wire is coupled over the ground.Collect 8 groups of data by scanning each line of induction.By scanning each group drive wire successively, repeat these steps 8 time, last, obtain 64 groups of data plots of whole front panel.

Below go through the principle of work of mutual capacitance touch panel.At first, with reference to figure 7, Fig. 7 illustrates the circuit model of the touch-sensitive area unit of Fig. 6, in the touch-sensitive area unit, shown in Fig. 6 and 7, drive point and induction point is arranged, just corresponding to driving district and the induction zone of Fig. 6.2 mutual capacitance (C have been formed between the two _DS) and self-capacitance (C separately _D, C _S).

The circuit model of Fig. 7 can be described as a schematic diagram, shown in 8 figure.Among Fig. 8, be connected with mutual capacitance between drive point and the induction point, drive point and induction point pass through self-capacitance ground connection separately respectively, and induction point is connected to the electric charge induction circuit by resistor, drive point resistors in series and galvanometer, galvanometric other end ground connection.Be excited when drive point, field is projected onto induction point.When inductor is not sensed object, C _DSIn the capacitive coupling point keep relative stability.

On the other hand, when an object such as finger are close to sensor, be equivalent to form the circuit of Fig. 9 this moment, the equivalent electrical circuit that the expression finger brings in the dotted line of top as shown in Figure 9, can be upset C _DSElectric field.Finger can be considered to a point and be connected to virtual field.In this case, electric field flows to a lower finger point from a higher potential point.Finger effectively is diverted to ground with the part electric field, so the amount that is connected with induction electrode of electric field reduces, i.e. C _DSThe electric capacity that falls, this operation is referred to as " shunt mode ".

As Figure 10, the finger the closer to the time, object and electrode (C _DFAnd C _SF) between electric capacity increase considerably.From the electric field of drive electrode capacitive coupling object, as the bolter of whole object electric field.Electric field is known the increase of induction electrode and effectively the time, C _DSIncrease.This phenomenon is called " transmission mode " or " human transmission effects ".

In fact, shunt mode and transmission mode all are simultaneous, but touch the main shunting principle that relies on.In order to ensure the touch panel stable operation, must stop transmission mode to control touch.In this case, ITO electrode and finger (C _DF﹠amp; C _DS) between electric capacity, with C _DSBy comparison must be little, so human transmission effects can be left in the basket.Therefore,

C _DS＞＞C _DF?&?C _SF (6.1)

And

$C_{\mathrm{SF}}\≈C_{\mathrm{DF}}={\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\left(\mathrm{glass}\right)}\frac{A}{d}---\left(6.2\right)$

A here and d represent the distance between overlapped district area and finger and electrode layer respectively.

In order to ensure the stable operation of touch panel, must guarantee the operation of shunt mode, rather than human transmission mode.Can calculate and keep required finger of shunt mode operation and the critical separation distance between the ITO layer.Equation (6.1) and (6.2) are if C _DS=2pF, ε _(glass)=4 and finger and the overlapped district of electrode area A _MAX=1.96x10 ^-5M- ²(being r=2.5mm).Critical separation distance D _MINBe 0.1mm, so the thickness of cover glass enough stop transmission mode to become to take as the leading factor usually.

Detection method

Existing detection method is all accurate and complicated than the application's mode, generally all can use the ASIC controller.Among the application, touch can be by surveying C _DSThe drop-out value of electric capacity uses two kinds of methods to survey this variation.First method is the induction point of measuring voltage coupling, and it requires sensor circuit that high output resistance is arranged.The voltage of induction point can pass through formula (6.3) and obtain.

ΔV _S＝(1+C _S/C _DS) ^-1ΔV _D (6.3)

Therefore, at induction point (Δ V _S), C _DSBe directly proportional with the AC compounent of being surveyed.Because the signal that obtains by this method is very little and moment, and precisely controls C _DSWith stray capacitance C _SBe to be difficult to realize, so this method degree easy to use is relatively poor.

Second method couples together the line of induction and charge amplifier, and perhaps each line of induction all is connected with a charge amplifier, and for example, the operational amplifier compositor as shown in figure 11.The small amount of charge that capacitive coupling produces, electric charge is forced to flow to upper channel, is stored among the feedback condenser C, and is transformed into the voltage output Vout of readability, therefore touches the minimizing that can be considered to flow of charge.This detection method has produced a better output drive strength, and in charge amplifier circuit, output gain signal can be changed by changing feedback capacity.As shown in figure 11, described electric charge induction circuit comprises charge amplifier, charge amplifier feedback condenser in parallel.Wherein, described each induction point all is connected with a charge amplifier.

Control system

Figure 12 shows that the block diagram of control system.This system comprises touch-screen, electric charge induction circuit, sample-and-hold circuit, Port Multiplier, analog to digital converter and controller.The output signal of touch panel is through the electric charge induction circuit, after obtaining by induction as above, output signal is buffered in the sample-and-hold circuit, sample-and-hold circuit is to the processing of taking a sample of this signal, and by the simulation Port Multiplier signal that stores is supplied to the ADC converter successively, the numeral output after the conversion is sent to the MCU controller and carries out digital processing.

MCU sends pulse signal to drive touch-screen, and touch-screen returns induced signal to the electric charge induction circuit, and the charge amplifier (not shown) amplifies signal.

The result

The application's touch panel scan rate can reach 100Hz, and the corresponding response time is 10ms.This is enough fast for the mobile object on touch panel operation or the tracking panel.Optical clarity also is an advantage of this design, because panel construction comprises the ITO individual layer is only arranged.Transparency depends primarily on the thickness of ITO layer.On this prototype, the ITO coating is 700A, and the transmittance of being surveyed is 91%.In theory, the panel light transmission rate can reach 95%.

2 fingers are placed on example on the touch panel.According to the difference of finger pressure, the area difference that skin covers, common single touch can cover 1 to 4 sensor.The minimizing amplitude of the charge amplifier output that finger pressure can pass through reflects.This charge amplifier output is adjusted to several depth level before showing by the ADC digitizing and on screen.

Data according to calibration can be located focus, and image can be accomplished to handle in real time and improve resolution, and some DSP algorithms insert as the sub-pixel of having reported.In this stage, can use bilinear interpolation increases panel resolution rate, from hardware resolution 8x8 to virtual resolution 15x15.Two adjacent datas are divided equally, inserted into new data, in order to increase resolution dividing the new numerical value that draws equally.

Figure 13 at diverse location, points different pressure and multiple spot result of detection figure to the finger touch that is respectively shown in Figure 15.Synthetic image after improving resolution, show how accurate hotspot graph picture and touch after coordinate more accurately.

Sum up and comparison

In a word, that the design of proposed individual layer projecting type capacitor formula touch panel has is simple in structure, permanance strong, the high grade of transparency, multiple point touching electric capacity and the low advantage of cost, and it is not influenced by surface blot.Single layer structure also can be used for curved substrate, and but, the quantity that the I/O of design connects is 2x (NxM), supposes that resolution is NxM.

The design of being carried is not complicated as other two kinds of technology, but individual layer mutual capacitance method has the advantage that other technology does not have, and it has the structure of individual layer, and has optical clarity preferably with respect to double-deck mutual capacitance.It utilizes various method for scanning, reduces the quantity of required sensor chip.Measuring mutual capacitance is to see through to detect electric charge, but not directly measures self-capacitance, has eliminated the necessity of using glass-chip to combine with sensor chip like this.All these advantages so that integrating process are simple more and cost is lower.Therefore, the individual layer mutual capacitance is the substitute of projecting type capacitor touching technique, to realize function, the balance of performance and cost.

By using individual layer projecting type capacitor formula touch panel of the present invention, make project organization simple, the permanance height, the transparency height, multiple point touching electric capacity and cost are low, and not influenced by surface blot, and single layer structure also makes it can be used for curved substrate.

It should be noted that at last above embodiment is only in order to describe technical scheme of the present invention rather than the present technique method is limited.

Claims (3)

1. touch screen control system, comprise touch-screen, touch induction circuit, sample-and-hold circuit, Port Multiplier, analog to digital converter and controller, the output signal of described touch-screen is through the electric charge induction circuit inductance, output is buffered in the sample-and-hold circuit, sample-and-hold circuit is to the processing of taking a sample of this signal, by the simulation Port Multiplier signal that stores is supplied to the ADC converter successively, numeral output after the conversion is sent to the MCU controller and carries out digital processing, described touch induction circuit comprises drive point and induction point, connect mutual capacitance between the two, drive point and induction point pass through self-capacitance ground connection separately respectively, induction point is connected to the electric charge induction circuit by resistor, drive point resistors in series and galvanometer, galvanometric other end ground connection.

2. the described system of claim 1 is characterized in that, described electric charge induction circuit comprises charge amplifier, charge amplifier feedback condenser in parallel.

3. the described system of claim 2 is characterized in that, described each induction point all is connected with a charge amplifier.

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