RU2399949C1 - Method of determining manipulator coordinates on touch panel - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method of determining coordinates on touch panel for entering data into a computer, game consoles, POS terminals and data panels is characterised by that a stream of modulated radiation of electromagnetic waves in the infrared region, which covers the surface of the touch panel, is generated over the surface of the touch panel using at least one radiator. Electromagnetic waves reflected from the manipulator near the surface of the touch panel are received using at least two spatially spaced apart receivers. Phase difference of the modulated signals is measured on radiators (radiator) and receivers. Coordinates of the manipulator on the touch panel are calculated from the ratio of phase difference.

EFFECT: broader functional capabilities and field of using the touch panel, high accuracy of determining coordinates of contact points using few radiators and receivers in the infrared region.

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Description

The invention relates to the field of computer engineering and electronics, in particular to methods for entering information into computers, game consoles, POS terminals, information boards, etc. and can be used in instrumentation.

Currently, there are eight main methods for determining coordinates on touch panels that differ in principle of operation. It:

- Resistive;

- Capacitive;

- Projection-capacitive;

- Surface acoustic waves (SAW);

- Acoustic Pulse Recognition (APR);

- Electromagnetic (induction);

- Scanning by infrared laser beams;

- Creating a lattice of infrared laser beams.

The resistive method consists in creating two thin, optically transparent (light transmission up to 75%) electrically conductive layers (for example, based on indium oxide - In ₂ O ₃ ), separated by a thin air gap of 25-90 microns wide. The gap is set by a grid of point polymer insulators applied to one of the surfaces. Along the edges of the panel are applied electrical tracks with low electrical resistance. When a certain pressure is applied to the panel, the layers are closed. Accordingly, a resistive four-terminal network is formed and the ratio of the resistance points can be used to calculate the coordinate of the closure point (http://www.touchgames.ru/eng/products/sensor_panels/resistive touch / Resistive touch - resistive touch panels).

The disadvantage of the above method is the effect of aging of the resistive layer on the accuracy of determining the coordinate of contact.

The capacitive method is to create an electrically conductive layer on a glass panel. The electrodes located at the corners of the screen supply alternating voltage to the conductive layer. When you touch the screen with your finger or other conductive object, a current leakage appears. Current in all four corners is recorded by sensors and transmitted to the controller that calculates the coordinates of the touch point (http://ru.wikipedia.org/wiki Touchscreens. Capacitive touchscreens).

The disadvantage of the above method is a decrease in performance when using a stylus or gloves.

The projection-capacitive method consists in creating a system of electrodes - electrically conductive microstrips on the insulator. Usually they are made in the form of two mutually perpendicular combs. Electrode capacitance is monitored. When a finger approaches the surface of the panel, the capacitance of the electrodes changes, which is recorded, and the touch point is calculated (http://ru.wikipedia.org/wiki Touchscreens. Projection-capacitive touchscreens).

The disadvantage of the above method is a decrease in performance when using a stylus or gloves.

The surfactant-based method consists in creating a piezoelectric emitter of an acoustic pulse along the edge of the glass screen, where a system of reflectors is created in the form of notches on the glass, located at an angle of 45 °. In this case, the initial pulse of a surface acoustic wave splits into a series of pulses successively crossing the screen surface. On the opposite side of the glass screen there are also reflectors in the form of notches reflecting acoustic pulses into the ultrasound receiver. Touching the surface of the finger screen dampens the amplitude of the pulse, which makes it possible to determine, by the time of arrival of pulses with a reduced amplitude, the coordinate of the touch. The second coordinate of the contact point is determined similarly (http://www.touchgames.ru/eng/products/sensor_panels/saw touch SAW touch - SAW touch panels).

The disadvantage of the above method is the need to use glasses of sufficiently large thickness to prevent attenuation of ultrasound.

A method of recognizing acoustic pulses is to register the sound generated at the touch point of the glass panel by several receivers, and to calculate, based on the time of arrival of the pulses, the coordinates of the sound source (http://blogwar.ru/article Touch screen. Touch screens APR (acoustic pulse recognition) .

The disadvantage of the above method is the need to ensure high noise immunity of the registration system of acoustic pulses.

The electromagnetic or induction method uses a stylus containing an antenna and a resonant circuit. Transceiver inductors are located under the touch panel. They create an electromagnetic field at the resonant frequency of the stylus loop, an alternating electric current is generated in the stylus circuit, which leads to the radiation of the stylus antenna of the corresponding electromagnetic field, which is picked up by the coils of the touch panel. By the amplitude of the signals on the coils, the coordinates of the stylus are restored (http://ru.wikipedia.org/wiki Touch screens. Induction touch screens).

The disadvantage of the above method is the mandatory use of a special stylus containing a resonant circuit.

There is a known method of scanning the surface with infrared laser beams, proposed by Microsoft (TOUCHWALL: MULTI-TOUCH WALL FROM MICROSOFT. Business Press. Electronic Edition, No. 58 (431) - 59 (431) of 05.23.08).

The method consists in scanning the surface of the panel with three laser beams and fixing the reflection of these rays from the manipulator with a photodetector. Knowing the law of change in time of the tilt angles of the scanning beams and fixing the moments of the intersection of the rays with the manipulator by the signal of the photodetector, we can calculate the coordinate of the manipulator.

The disadvantage of the above method is the need to use movable structural elements to ensure scanning rays. The use of movable elements leads, as a rule, to an increase in the cost of devices and a decrease in their reliability.

By technical nature, the closest to the proposed method is a method of indicating the coordinates of the touch panel based on the creation of an infrared laser beam array (Patent No. CN20071073148 20070130, Inventors: YALIN GUO [CN]; JIAN MA [CN]; XIAODONG XIE [CN]; CHUNSHENG ZUO [CN], Applicant: BEIJING HITEVISION DIGITAL MED [CN] Infrared touch screen based input method and system. Publication date: 2008-08-06).

The method consists in using two pairs of lines of IR emitters and receivers located mutually perpendicularly and forming a beam array above the panel. Approaching the surface of the panel of a finger or stylus leads to optical overlap of a number of vertical and horizontal rays, which allows us to judge the point of contact.

The disadvantages of the prototype are:

- The need to use rulers with a large number of emitters and receivers, which leads to a high cost of the product and reduces its reliability;

- A relatively high error in determining the coordinate of the contact, corresponding to the step of the location of the emitters and receivers on the rulers.

The technical result of the proposed method is to expand the functionality and scope of the touch panel by creating a method for determining the coordinates of the touch panel for entering data into computers, game consoles, POS terminals, information boards, etc. with a small number of emitters and receivers of the infrared range, which has high accuracy in determining the coordinates of the contact point.

In order to achieve a technical result in a method for determining the coordinates of a manipulator on a touch panel for entering data according to the invention, a modulated radiation stream of infrared electromagnetic waves covering the surface of the touch panel is created using at least one emitter above the surface of the touch panel, and the reflection is received from a manipulator located in a stream of modulated radiation, electromagnetic waves using at least two spatially separated receivers, measure the phase differences of the modulated signals at the emitter (emitters) and receivers, after which the coordinates of the manipulator on the touch panel are calculated by the ratios of the phase differences. In addition, the reception of electromagnetic waves reflected from the manipulator, located in the modulated radiation stream, is carried out using at least three spatially separated receivers, after which the radius of the manipulator is additionally calculated, and the modulated radiation flux of electromagnetic waves of the infrared range is created using, at least two emitters switched on in turn, and the coordinates of the manipulator on the touch panel are obtained by averaging the coordinates calculated from the measurement results phase of the modulated signals during the operation of each emitter.

Comparison of the proposed method with the closest analogue allows us to claim compliance with the criterion of "novelty", and the absence of distinctive features in the analogues allows us to judge compliance with the criterion of "inventive step".

Preliminary tests confirm the possibility of wide industrial use.

Figure 1 presents a diagram of a device for implementing the inventive method, Figure 2 presents a diagram for calculating the coordinate, Figure 3 presents graphs of the phase versus the displacement of the contact point for multiple modulation frequencies. Figure 4 presents an example of a functional block diagram of a device that implements the inventive method.

Figure 1 is a variant of the circuit of the device according to the claimed method, containing four emitters and four receivers: the first emitter - 1; the first receiver is 2; the second receiver is 3; second emitter - 4; third emitter - 5; the third receiver is 6; the fourth emitter is 7; the fourth receiver is 8; fingerprint of a manipulator (finger) - 9.

Figure 2 is a diagram for calculating the coordinate. The first emitter is at point 0 (one of the corners of a rectangular screen). The first receiver is at point L ₁ , the second receiver is at point L ₂ . The fingerprint of the manipulator (finger) is at the point with coordinates (x, y) and has a radius r ₀ .

Figure 3 - graphs of the phase versus the displacement of the contact point for multiple modulation frequencies. Curve 10 is the phase versus displacement for frequency v. Curve 11 is the dependence of the phase on the bias for the frequency ν ₁ = 1 / 2ν. Curve 12 is the dependence of the phase on the displacement for the frequency ν ₂ = 1 / 2ν ₁ .

Figure 4 - an example of a functional block diagram of a device according to the claimed method contains one emitter and two receivers: generator - 13; modulator - 14; first emitter (laser LED) - 1; the first receiver (photodiode) - 2, the second receiver (photodiode) - 3; preamplifiers - 15, 16; band-pass filters - 17, 18; amplifiers with automatic gain control - 19, 20; phase detectors - 21, 22; microprocessor device - 23.

The method is implemented as follows.

The emitters create a modulated infrared radiation stream in a wide angle horizontally and in a narrow angle - vertically (see Figure 1). Existing low-power semiconductor lasers allow this. The modulation frequency ν is selected based on the size of the panel. Preferably, the maximum panel size does not exceed 1/4 of the modulation wavelength λ = c / ν, where c is the speed of light. This is necessary to unambiguously determine the phase difference and, therefore, to calculate the coordinates of the manipulator (stylus, finger, etc.) on the entire surface of the panel. The radiation is reflected from the surface of the manipulator and enters the receivers. Because Since the radiation is modulated, the reflection points can be determined from the phase differences and, for example, to calculate the "center of gravity" from them. If the contour of the reflection points expands, then this can be interpreted as a click. The touch panel may be a transparent surface, behind which is, for example, a liquid crystal screen, or an opaque surface onto which the image is projected.

Consider the geometry of reflection from a cylindrical object (manipulator, see Figure 2). The first emitter is located at the origin - point 0 (one of the corners of a rectangular screen). The first receiver is at point L ₁ , the second receiver is at point L ₂ . The fingerprint of the manipulator (finger) is located at the point with coordinates (x, y) and has a radius r ₀ .

From the equality of the angles of incidence and reflection:

From the theorem on the sum of the internal angles of a triangle:

From the sine theorem:

The geometry of the emitter and receivers is known, because device design should be determined:

From phase measurements of the path from the emitter to the reflecting object and further to the receivers, we have:

Substituting (5, 6, 11, 12) into (7-10), we obtain, together with (1-4), a system with a smaller number of unknowns and equations.

Substituting (16) in (14), we obtain:

If r ₀ is known, then two measurements are sufficient to determine x and y. Moreover, the expressions (1-4; 13, 15, 17, for i = 1, 2) form a system of 10 equations for 10 unknowns: x, y, a ₁ , a ₂ , l ₁ , l ₂ , φ ₁ , φ ₂ , γ ₁ , γ ₂ . It is quite possible to simplify this system by analytical methods, but, nevertheless, it turns out to be necessary to numerically solve the system of transcendental nonlinear equations. To date, various iterative methods for solving such systems have been well developed, allowing to obtain a solution with a given accuracy. These are, for example, gradient methods (steepest descent method and descent method with calculation of gradient coordinates); Newton's method, etc. / G.Corn, T.Corn. Math reference. St. Petersburg, "Doe", 2003 /. Modern microprocessors (for example, type PIC18F4550) allow you to implement the solution of such systems of equations in real time.

If r ₀ is not known in advance, then at least one more measurement is necessary. In this case, the system of equations increases accordingly. To increase the accuracy of determining the center of gravity of the touch object, an approximating shape in the form of an ellipse can be selected. In this case, the system of equations and, accordingly, the number of necessary measurements will further increase proportionally.

That is, in other words, through phase measurements, three reflection points are determined, a circle is drawn through them and its center is determined. It is possible to determine 4 reflection points, draw an ellipse through them and determine its center of gravity. And so on. On the other hand, it is possible to divide the measurements into several groups, calculate from them a number of centers of gravity of the obtained figures and average the results. It should be noted that one measurement can take time on the order of units or fractions of microseconds. The manipulator at this time scale can be considered immobile.

Improving the accuracy of determining the coordinates and improving the reliability of the device that implements the inventive method is possible by increasing the number of emitters and receivers. For a number of applications, devices according to the claimed method may be optimal, containing at least two emitters and three receivers. In this case, due to the minimal technical complication of the device, a significant expansion of its functionality is achieved.

Let there are four emitters and four receivers (see Figure 1). Emitters can operate sequentially in a narrow spectral range to reduce the influence of external interference. Those. first the first emitter is turned on. In this case, the first and second receivers register reflected (indirect) radiation. The signals from the receivers and the signal from the emitter through a piece of cable of a given length are fed to the inputs of the phase detectors, which determine the values of the radiation path through the reflecting object to the receiver. Then (after a time of the order of a microsecond), the second emitter is turned on and the measurement process is repeated. And so on in a cyclical way.

As can be seen from Figure 1, on average, you can get N = 8 measurements of the path S _i from the emitter to the receiver through a reflecting object (finger). To determine 3 unknowns (x, y, r ₀ ), 3 measurements are required. The number of combinations of systems of equations is determined by the expression:

It is easy to see that the number of combinations of systems of equations with N = 8 is 56. By solving systems of equations and averaging the results, it is possible to increase the accuracy of determining the point of tangency.

IR radiation can be modulated by multiple frequencies. Silicon technology, well mastered by the industry, works well up to frequencies ν ~ 3 GHz. This wavelength λ = 10 cm. Accordingly, the size of the working area is _^1/4 of λ, ie 2.5 cm. It is enough to simply determine the phase with an accuracy of 1 degree. Thus, it is possible, using a fairly simple technique, to determine a coordinate with an error within 100 microns on sizes of the order of a few centimeters. If the size of the working area exceeds units of centimeters, and the requirement for submillimeter resolution is maintained, then it is possible to modulate the carrier infrared radiation with multiple frequencies, for example, ν ₁ = 1.5 GHz, ν ₂ = 750 MHz, etc. Then the phase analysis at the lower frequencies will indicate the part of the region where the source is located, and the measurement at the highest frequency will give the exact coordinate. Figure 3 presents the characteristic (periodic) dependence of the phase shift φ on the coordinate at multiple frequencies.

Let the manipulator be at the point X _i . Then, according to the phase shift at a frequency ν ₂ (less than 90 °), we determine that the stylus is in the interval (0-X ₂ ). According to the phase shift at a frequency of ν ₁ (more than 90 °), we determine that the stylus is in the range (X ₁ -X ₂ ). And finally, from the phase shift at the frequency ν, we determine the exact coordinate X _i . High precision is usually required for professional design applications.

Due to the fact that there are no methods for indicating (determining) coordinates on the touch panel in which one or two stationary emitters and infrared radiation receivers are sufficient, it meets the criterion of "novelty."

Due to the fact that the use of phase-sensitive electronics is not obvious for constructing infrared touch panels, the claimed invention meets the criterion of "inventive step".

The scope of devices based on the proposed method can be industry (CAD - design, 2D - modeling), the entertainment industry (computer games, game consoles, gaming machines), etc. The claimed invention is relatively simple to implement. The cost of electronic components for the implementation of this device is relatively low and can be further reduced by the production of specialized microcircuits in serial production, which will ensure competitiveness with existing analogues. Accordingly, the claimed invention meets the criterion of "industrial applicability".

Information confirming the possibility of carrying out the invention.

Functional diagram of a device that implements this method is presented in Figure 4.

The generator 13 creates a periodic signal, which is supplied to the modulator 14. The modulator changes the current through the first emitter 1 (laser LED) according to the law of the modulating signal.

Thus, the infrared radiation of the laser diode is modulated in amplitude. Infrared radiation reflected from the manipulator is fed to the first receiver 2 and the second receiver 3 (photodiodes), the load of which are pre-amplifiers 15, 16.

Since the laser LED radiation is modulated, the source modulating signal is allocated to the loads of the photodiodes, which is amplified by pre-amplifiers 15, 16 of the receiving devices and fed to the bandpass filters 17, 18. Bandpass filters emit a frequency band of 20 kHz ÷ 1 MHz with a center frequency equal to a frequency modulating signal. This eliminates the interference caused by other sources of infrared radiation. After filtering, the signals are amplified by amplifiers with automatic gain control 19, 20 and fed to the signal inputs of the phase detectors 21, 22. The signal inputs from the generator 13 are supplied to the reference inputs of the phase detectors, while a signal proportional to the phase difference of the emitted and received signals. These signals make it possible to determine the parameters S ₁ and S ₂ (see expression (12)). From the outputs of the phase detectors, the signals are sent to the microprocessor device 23 for subsequent processing - solving the above system of equations and determining the coordinates of the manipulator on the panel.

The following radio elements (microcircuits) can be used in the device circuit:

Generator 74AC00; AD831 modulator pre-amplifiers AD8099; amplifiers with AGC AD8367; phase detectors AD8302; microprocessor device PIC18F4550; laser diode HFE 4084-322; BPW 24R photodiodes.

All the elements necessary for the implementation of the proposed method, IR emitters, IR receivers, phase detectors, amplifiers, processors, etc., exist and are commercially available. There are no fundamental difficulties for the development and production of specialized microcircuits.

Thus, the present invention can be practiced.

Claims (3)

1. The method of determining the coordinates of the manipulator on the touch panel for entering data into computers, game consoles, POS-terminals, information boards, characterized in that above the surface of the touch panel using at least one emitter create a stream of modulated radiation of electromagnetic waves IR range covering the surface of the touch panel, receive electromagnetic waves reflected from the manipulator located in the modulated radiation stream using at least two spaces venno spaced receivers measure the phase difference of the modulated signal on the emitter (emitter) receivers and then the coordinates of the manipulator on the touch panel is calculated from the phase difference ratios. 2. The method according to claim 1, characterized in that the reception of electromagnetic waves reflected from the manipulator located in the modulated radiation stream is carried out using at least three spatially separated receivers, after which the radius of the manipulator is additionally calculated. 3. The method according to claim 1, characterized in that the flow of modulated radiation of electromagnetic waves of the infrared range is created using at least two emitters switched on in turn, and the coordinates of the manipulator on the touch panel are obtained by averaging the coordinates calculated from the results of measurements of the differences phases of modulated signals during operation of each emitter.

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