WO2012073173A1

WO2012073173A1 - Improved method for determining multiple touch inputs on a resistive touch screen

Info

Publication number: WO2012073173A1
Application number: PCT/IB2011/055321
Authority: WO
Inventors: Andrea Celani; Nicolò PASTORE
Original assignee: Haptyc Technology S.R.L.
Priority date: 2010-11-29
Filing date: 2011-11-28
Publication date: 2012-06-07
Also published as: ITMI20102210A1

Abstract

The present invention relates to a method for interpreting zoom or rotation gestures on a resistive touch screen. The method comprises the steps of touching the first layer (2A) at two points (PI, P2); powering said first layer (2A) with a predetermined voltage value (Vcc), while said first layer (2A) is being touched at said points (PI, P2); detecting, at a first time (t1), a first value of current (I_2x) and a third value of current (I_2y) circulating in said first layer (2A) and subtracting a first threshold value (I_thdx) from said first current value (I_2x) to generate a first processed current value (I_2x,t1) and subtracting a second threshold value (I_thdy) from said third current value (I_2y) to generate a third processed current value (I_2y,t1); detecting, at a second time (t2), a second value of current (Ι_2x') and a fourth value of current (I_2y') circulating in said first layer (2A) and subtracting said first threshold value (I_thdx) from said second current value (Ι_2x') to generate a second processed current value (I_2x,t2) at said second time (t2) and subtracting said second threshold value (I_thdy) from said fourth current value (I_2y') to generate a fourth processed current value (I_2y,t2); defining a first magnification factor (K_current,x) along a first axis (2C) using formula (I) defining a second magnification factor (K_current,y) along a second axis (2D) perpendicular to said first reference axis, using formula (II) defining an overall magnification factor (K_current), using formula (III). The method is characterized in that it comprises the step of defining a modulation factor of a object (K_object), which is proportional to the distance between said two touch points (PI, P2) using formula (IV) wherein μ designates a modulation parameter, K_current designates said overall magnification factor and K_object designates said modulation factor.

Description

DESCRIPTION

" Improved method for deterniining multiple touch inputs on a resistive touch screen"

Related art

The contents of patent application PCT/IT2009/000239 by the Applicants hereof is incorporated herein by reference.

Technical field

The present invention relates to an improved method for interpreting gestures on a resistive touch screen.

Background art

A number of input devices are available in the prior art, for performing a variety of operations in an IT system, such as i ATMs (Automated Teller Machines), kiosks, POS (Points of Service), but especially in electronic devices such as PDAs (Personal Digital Assistants), mobile phones, notebooks, laptops, MP3 readers, etc.

These operations generally consist in moving a cursor and/or selecting a portion of an image on a screen, but also in scrolling, panning and zooming an image on the screen.

For example, input devices may include push buttons, switches, keyboards, mice, trackballs, touchpadSj joysticks, touch screens and the like. Each of these devices has advantages and drawbacks, which are accounted in the design of the IT system.

In recent times, additional features have been provided to the user, by using gestures as screen input devices, i.e. using one or more fingers of one or both hands which touch the screen at different points and move within the screen area to create, when properly interpreted, features such as zooming or rotation of an object displayed on the screen as a portion or the entirety of: a text, an image, a vector figure, etc.

US 5,612,719 and US 5,590,219, issued to Apple Computer, Inc., disclose some uses of gestures. The processing for interpreting user gestures on the screen requires the use of complex algorithms which only ensure proper interpretation when using high or very high resolution screens and processors having an adequate processing power.

Interpretation of gestures on a resistive touch screen involves additional difficulties, because its control circuitry cannot determine multiple touch inputs on its surface.

For deterrnination of multiple touch inputs on a resistive touch screen, reference is made herein to the disclosure of patent application PCT/IT2009/000238. Particularly, the method as disclosed in patent application PCT/TT2009/000238 teaches to read the value of a current that flows in one of the two layers of the resistive screen when that layer is simultaneously touched at two distinct points PI and P2 and is powered with a voltage equal to the power-line voltage. For example, the coordinates X of the touch points PI and P2 are used to process the current value and obtain a modulus value Δχ, representative of the difference along the x axis of the first layer between the coordinates of the first touch point PI and the second touch point P2. Once the modulus value Δχ has been obtained, and knowing the coordinates xc,yc of the midpoint P0 with respect to the x,y coordinates of the two touch points, the x coordinates of the two points PI e P2 may be calculated by addition or subtraction of the modulus value Δχ to or from the coordinates xc of the midpoint P0.

The modulus value Ay, representative of the difference along an axis perpendicular to the first axis within the first layer, is obtained likewise; once the modulus value Ay has been obtained, the y coordinates for the two points PI and P2 may be calculated by addition or subtraction of the modulus value Ay to or from the coordinates yc of the midpoint P0.

In patent application PCT/IT2009/000238, also referring to Figure 1 , the coordinates of the midpoint P0 are estimated by detecting the read voltage from a reading terminal VI or V2 of one of the two links defined by the resistors Rl 1, R12 and 3 and the resistors R7, R8 and R3 respectively, when the screen is simultaneously touched at the two points PI and P2.

Technical problem

The above considerations clearly show that a need is highly felt of interpreting gestures on a resistive touch screen.

Hence, the present invention is based on the problem of providing a method that has such functional features as to fulfill the above need, while obviating the above prior art drawbacks.

Technical solution

This problem is solved by a method for interpreting gestures on a resistive touch screen as defined in claim 1.

Advantageous effects

With the present invention, a method is provided of interpreting gestures on a resistive touch screen without changing the construction of a common resistive touch screen, such as of the 4-wire, 5-wire or 8-wire screen.

The present invention may particularly find application in a variety of electronic apparatus such as ATMs (Automated Teller Machines), kiosks, POS (Points of Service) apparatus, but especially in electronic devices such as PDAs (Personal Digital Assistants), mobile phones, notebooks, laptops, MP3 readers, etc.

Brief description of the drawings

Further features and advantages of the method of the present invention will result from the following description of one preferred embodiment thereof, which is given by way of illustration and without limitation with reference to the accompanying figures, in which:

- Figure 1 shows a diagrammatic view of the panel when it is touched at two points with the coordinates of the points being determined along an axis, according to the present invention;

- Figure 2 shows a different diagrammatic view of the panel of Figure 1, in which the centering problem is identified;

- Figure 3 shows the same diagrammatic view as the panel of Figure 2, with the coordinates of the points being determined along an axis, according to the present invention;

- Figure 4 shows a diagrammatic view as the panel of Figure 2, with the coordinates of the points being determined along another axis, according to the present invention;

- Figures 5 and 6 show a different diagrammatic view of the panel of Figure 1, in which the ambiguous orientation problem is identified;

Detailed description

Centering issue

Referring to the description of PCT/IT2009/000238 and to Figure 1, which shows a circuit model of a resistive touch screen, if pressure is exerted, for instance by fingers, at two points PI and P2, the latter being shown for simplicity to have a x coordinate equal to that of the touch point PI and, if only one layer of the two layers that form the screen is powered, and the other is held floating, then the current 12 that flows in the powered layer increases with respect to the condition in which the touch screen is touched at a single touch point.

Particularly, in Figure 1 the layer that is powered with the voltage Vcc is, for instance, the layer representative of the y coordinates, whereas the layer that is held floating is, for instance, the one representative of the x coordinates. The current 12 that flows in the powered layer (i.e., in the particular case of Figure 1, the layer representative of the y coordinate) increases as compared to the one that would be obtained if the screen were touched at a single touch point. Such increase is caused by the fact that by touching the first screen layer at two points, a parallel path is introduced in the lower panel, (here representing the x coordinate).

Particularly, the current 12 also flows through the links defined by the resistors Rl 1 , Rl 2, R3 and the resistors R7, R8 and R3 respectively.

In PCT/IT2009/000238, the coordinate of the midpoint P0 is estimated by evaluating one of the two possible read voltages VI and V2 provided by common resistive touch screen control circuitry.

This estimate simplifies the method for determining multiple touch inputs on a resistive touch screen, but introduces an error caused by the influence of one of the two touch points PI or P2 with respect to the selected reading terminal VI or V2.

With the above in mind and referring to Figure 2, the present inventors found that the touch point PI, i.e. the one placed, for instance, at the top right, will "influence" more the reading terminal VI, whereas the touch point P2, placed for instance at the bottom left, will "influence" more the reading terminal V2.

This different influence on the reading terminals VI, V2 is caused by the fact that the average voltage evaluated in one of the two reading terminals VI or V2 is obtained by weighting the two touch voltages by their impedance to the reading terminal.

Considering the reason for the different influences on the reading terminals VI, V2, in the method for determining multiple touch inputs on a resistive touch screen with improved precision, also referring to Figure 3 (for the Y coordinates of the points PI and P2), and Figure 4 (for the X coordinates of the points PI and P2), the step of obtaining the coordinates P0xc,P0yc of the midpoint P0 is carried out by first detecting a first read voltage VI (reading terminal VI) and a second read voltage V2 (reading terminal V2) and then by processing a read voltage Vxc, Vyc that equals an average value between the first read voltage VI and the second read voltage V2 (by appropriately changing the power nodes and the read nodes) to obtain said coordinates POxc, POyc of the midpoint P0.

It shall be noted that reference can be made to PCT/IT2009/000238, incorporated herein, for calculation of modulus values Δχ and Ay of the two touch points PI and P2 relative to the coordinates of the midpoint P0 as well as the coordinates x,y of said two touch points PI and P2, as shown by the block diagrams of Figures 3 and 4.

For the purposes of the present invention it shall be noted that the modulus value Δχ (and likewise the modulus value Ay) is calculated by powering the first layer 2A (e.g. the flexible outer layer) with a voltage value Vcc, while such first layer 2A is touched in the first point PI and the second point P2 respectively; by detecting a first current value I2,x for the current flowing in the first layer 2A, i.e. the layer powered with the voltage value Vcc; by processing the first current value I2,x to determine a first modulus value Δχ representative of the coordinate difference along the axis 2C (e.g. the x axis) of the first layer 2A between the coordinates of the first touch point PI and those of the second touch point P2.

The method may include, also with reference to Figure 3, averaging of the read voltages VI and V2 to obtain an estimate of the average voltage Vyc, representative of the coordinate POyc of the midpoint P0, which is more accurate than the estimate that can be obtained by traditional methods.

For instance, the average voltage Vyc may be calculated using the following formula:

a * Vl + fi * V2

Vyc

2 in which a and β are two parameters that account for the impedance with which the two touch points PI and P2 control the related voltages VI and V2.

These two parameters a and β may be obtained iteratively, may be calculated by a complex model of the resistive panel, or may be also saved in a previously prepared lookup table.

Likewise, also referring to Figure 4, a more accurate estimate of the coordinate POxc of the midpoint P0 consists in averaging the read voltages VI and V2 using weights γ, δ, i.e. according to the following formula:

y * Vl + S * V2

Vxc = -

2

in which γ are δ are two weights or parameters that account for the impedance with which the two touch points PI and P2 control the related voltages VI and V2.

Also in this case, the two parameters γ and δ may be obtained iteratively, may be calculated by a complex model of the resistive panel, or may be also saved in a previously prepared look-up table.

A more precise estimate of the read voltages Vyc,Vxc will also provide a more precise estimate of the x, y coordinates of the two touch points PI, P2.

Thus, once the modulus value Δχ and the modulus value Ay have been obtained (as described in PCT7IT2009/000238), and knowing the coordinates POxc, POyc of the midpoint PO from the average read voltage Vxc, Vyc, the x and y coordinates of the two points PI e P2 may be calculated by addition or subtraction of the modulus value Δχ, Ay to or from the coordinates xc, yc of the midpoint PO.

Once an estimate of the voltage Vxc, Vyc of the midpoint PO has been obtained, the spatial coordinates POxc and POyx may be obtained by the method in a conversion step, for converting such voltage values Vxc, Vyc, in proportion to the size of the resistive panel, into the coordinates POxc and POyc.

Such conversion step requires knowledge of the size of the resistive panel (e.g. its pixel size according to the graphic display with which the touch screen panel is coupled, or the size in meters, etc.).

Preferably, the conversion step of the method is based on pixel conversion. This ensures direct use of the coordinates by the graphic processing system that actively controls the graphic display mounted with the resistive panel.

Characteristic parameters of the resistive panel are known by the skilled person to be, for instance, the y axis dimension Heightpj_xd_j or the x axis dimension Height_Pj_xei_>x of the pixel graphic display.

Once the Height_pj_xdj and Height_p^^ values are known, the coordinates POxc and POyc may be calculated, e.g. using the following formulas:

- for the coordinate POyc of the midpoint PO:

Heig t^ , VI + V2

P0yc =

Vcc 2

- for the coordinate POxc of the midpoint PO:

roxc ^{H ght}^* * ^{VI + V2}

Vcc 2

wherein:

- Vcc is the voltage supplied to the panel or more generally the potential difference between one terminal of the panel and the other terminal of the panel with which the voltage reference is connected (ground reference of the circuit). Ambiguity issue

Nevertheless, also with reference to Figures 5 and 6, the electronic circuitry of the resistive touch screen can identify two pairs of touch points ε and λ. using the acquired information (i.e. the coordinates P0xc,P0yc of the midpoint P0, Ay and Δχ, see Figure 5).

Particularly referring to Figure 6, i can be noted that both pairs of touch points ε and λ have the same coordinates POxcJPOyc, the same value Ay and the same value Δχ as the midpoint P0.

Each pair ε or λ, unless they have identical x or y coordinates, is oriented along a diagonal of a hypothetical Cartesian reference plane. Each pair is also in specular orientation with respect to the other.

In other words, the electronic circuitry of the resistive touch screen cannot determine, with the acquired information, whether the two touch points PI and P2 are oriented in the direction of extension of the pair of touch points ε or in the direction of extension of the pair of touch points λ, as both pairs ε and λ fulfill the reading conditions.

Therefore, the circuitry has to solve the problem of ambiguous orientation of the two touch points PI and P2, which may cause wrong interpretation of the x and/or y coordinates of the two touch points.

Particularly, as shown by way of example in Figure 6, the pair of touch points ε may extend along a top right to bottom left diagonal (i.e. the first and third quadrants of a Cartesian reference system centered in the midpoint P0xc,P0yc ) whereas the pair of touch points λ may extend along a top left to bottom right diagonal (i.e. the second and fourth quadrants of a Cartesian reference system centered in the midpoint P0xc,P0yc) or vice versa.

In order to obviate the problem of ambiguous orientation of the two pairs, referring to the situation as shown in Figure 6, the method may comprise the step of monitoring the difference between the potential at the reading terminal VI and the potential at the reading terminal V2, to determine the orientation of the axis that joins the two touch points PI and P2 with respect to the supply axis.

The present inventors found from experimental tests that the reading terminals VI and V2 are controlled with a different impedance, proportional to the distance from each of the two touch points PI and P2.

Particularly, still considering the diagram as shown by way of example in Figure 6, since the point PI is closer to the reading terminal VI, it has a lower impedance than the touch point P2. The touch point PI controls the temiinal VI with a lower impedance than the touch point P2, that controls it with a higher impedance. The touch point PI will force a voltage close to that of the point PI, which is higher (according to the voltage supply of the panel) than that of the touch point P2.

Once this has been determined concerning the pair of touch points ε, the method may advantageously comprise a step of checking whether the voltage of the reading terminal VI is higher than the voltage of the reading terminal V2 of the first layer 2A (see Figure 3), and if it is, determining the coordinates Ply of said first touch point PI along the axis 2D (i.e. the y axis) of the layer 2B by summing half the value Ay to the coordinate POyc of the midpoint PO for such axis 2D of the layer 2B of the panel 1.

In other words, the y coordinate of the touch point PI of the pair ε can be calculated using the following formula:

P\_v - P0yc +—

y 2

where POyc is the y coordinate of the midpoint PO.

Likewise, the y coordinates may be determined for the second touch point P2, by checking whether the read voltage VI is higher than the read voltage V2 of the layer 2A and, if it is, detenriining the coordinates P2y of the touch point (P2) along the axis 2D of the layer 2B by subtracting half of said second value Ay from the coordinate POyc of the midpoint PO for such axis 2D of the layer 2B of the panel 1.

In other words, the y coordinate of the touch point P2 of the pair ε can be calculated using the following formula:

Ay

P2 = P0yc—

2

The same method also applies to the x coordinate of the touch points PI and P2 and the x coordinate of the touch point PI of the pair ε may be calculated using the following formula:

Δχ

P\ = P0xc +—

2

where POxc is the x coordinate of the midpoint PO,

whereas the x coordinate of the touch point P2 of the pair ε can be calculated using the following formula: P2_X = POxc

2

In other words, if the read voltage VI is higher than the read voltage V2, then the pair of touch points PI, P2 is oriented along a diagonal that passes through the first and third quadrants of a Cartesian reference system centered in the midpoint P0xc,P0yc and hence with respect to the coordinates of the midpoint PO.

This is caused by the fact that, if the touch points are oriented as a pair ε, then the touch point at the top right (i.e. PI as shown in Figure 6) will be closer to the reading terminal VI whereas the touch point at the bottom left (i.e. P2 as shown in Figure 6) will be closer to the reading terminal V2.

In this context, the two touch points PI, P2 have different potentials along the supply axis and the top right touch point (i.e. PI as shown in Figure 6) will have a higher potential than the bottom left touch point (i.e. P2 as shown in Figure 6).

This potential difference, in the conditions of the pair ε causes the potential of the reading terminal VI to be higher than the potential of the reading terminal V2.

Concerning the pair of touch points λ, the method advantageously comprises checking whether the voltage of the reading terminal VI is lower than the voltage of the reading terminal V2 of the first layer 2 A and if it is, deterrnining the coordinates Ply of the first touch point PI along the axis 2D of the second layer 2B by summing half the value Ay to the y coordinate POyc of the midpoint PO for the axis 2D of the second layer 2B.

In other words, the y coordinate of the touch point PI of the pair λ can be calculated using the following formula:

Δν

Pl_v = P0yc +—

2

where POyc is the y coordinate of the midpoint PO.

Likewise, the y coordinates may be determined for the second touch point P2, by checking whether the read voltage VI is lower than the read voltage V2 of the layer 2 A and, if it is, determining the coordinates P2y of the touch point P2 along the axis 2D of the layer 2B by subtracting half of said second value Ay from the coordinate POyc of the midpoint PO for such axis 2D of the layer 2B of the panel 1.

In other words, the y coordinate of the touch point P2 of the pair λ can be calculated using the following formula: P2_y = P0yc -

2

The same applies to calculation of the x coordinate of the touch points PI and P2. Particularly, the x coordinate of the touch point PI of the pair λ can be calculated using the following formula: Pl_x = P0xc ^~ whereas the x coordinate of the touch point P2 of the pair λ can be calculated using the following formula:

Δχ

P2 = P0xc +—

2

It shall be noted that the method as described above may be used in any time discretization situation, both when the time distance between the first touch point PI and the second touch point P2 is lower than the time resolution of the electronic circuitry of the resistive touch screen panel 1 and when the time distance between the event of the first touch point PI and the second touch point P2 is higher than the time resolution of the resistive touch screen panel 1.

In other words, the method as described above is applicable either when the screen is touched at the two touch points PI and P2 substantially at the same time, or when the touch points PI and P2 are touched one after the other slow enough to allow detection by the control circuitry.

In the method, if the two touch inputs PI and P2 are made in such a manner as to allow time discrimination thereof by the acquisition electronics (i.e. within its time resolution), the coordinate of the first touch input made on the panel may be stored, until the second touch input occurs, Δχ, Ay (Δχ, Ay being calculated with the technique as described in PCT/IT2009/000238) and the coordinates POxc_^POyc of the midpoint P0 (the coordinates P0xc,P0yc of the midpoint P0 being calculated with the method as described in the present application or the technique as described in PCT IT2009/000238) are acquired, to calculate an absolute value of the distance between the stored coordinate of the first touch input made on the panel and all the assumed coordinates determined after the touch input P2, and to determine the x,y coordinate at zero distance from those that have been stored.

Particularly, in addition to storing the coordinate of the first touch point, e.g. the coordinate Plxm, Plym if the first touch point is PI, and waiting until the panel has not been touched at a second touch point, the method includes the steps of:

- calculating all possible coordinates for all the quadrants with the formulas y _ε ^■> 2 ^{j x}-^s 2 ' ^y- 2 ' y ~^£ 2 '

L ^ xc P2 . _= y ..c.

2 ^Ϊ -^-^¹ ^ — ^y _D2 XC + - 2 ³ 2

- calculating the distance between the stored coordinates Plx,Ply of the single touch point PI and all the calculated coordinates Ply_s, Ρΐχ ε, P2y_s, Ρ2χ_ε, Ρ1ν_λ, Ρ1χ_λ, P2y_ , Ρ2χ_λ

i.e.:

dl_l=Plxm-Plx_E

d2_l=Plxm-PlxJ.

d3J=Plxm-P2x_e

d4_l=Plxm-P2x_

or:

^'dl_2=Plym-Ply_s

d2_2=Plym-PlyJ,

d3_2=Plym-P2y_s

d4_2=Plym-P2y_

or as a geometric distance: dl_3=^(RxA77- Pl_{x s} +( ym- Pl_{y s}f

d2_3= - j(Plxm- Pl_x ) + (Piym- P2_{y e})²

The minimum distance value between the calculated coordinates Ρ^_ε, Ρ1χ_ε, Ρ2ν_ε, Ρ2χ_ε, Ρ1^_λ, Ρ1χ_λ, P2y_ , Ρ2χ_λ and the stored coordinates Plxm,Plym defines the point that is closest to the single touch point PI, in a single touch condition. Assuming that the first touch position is not considerably displaced between the single- touch input time and the multi-touch input time, then the determination of the multi- touch input coordinate that is closest to the single-touch input coordinate determines the quadrants of the axis of the two touch inputs.

Gestures issue

For improved usability of ATMs (Automated Teller Machines), kiosks, POS (Points of

Service) apparatus, but especially in electronic devices such as PDAs (Personal Digital Assistants), mobile phones, notebooks, laptops, MP3 readers, gestures are typically used whereby pressure at the two touch points PI and P2 quickly and easily triggers functions (such as zoom, rotation, etc.) that would be otherwise only available through pressure of one or more special keys or through exploration of menus of said electronic devices.

Magnification

Advantageously, the information concerning the current I_2x, I_2y (see Figures 3 and 4) circulating in the resistive touch screen 1 as a result of two touch inputs PI, P2 may be related to a modulation factor Kobj_ect of an object displayed on a screen, such as a text, an image, a vector figure, etc.

Particularly, measurement of currents in orthogonal panels at successive times provides the modulation factor Kobject of the object on the screen, using the following formula:

K ob .ject = " * K current

wherein μ designates a modulation parameter and Kcumnt designates said overall magnification factor.

It shall be noted that the overall magnification factor Kcmrent of the object is a function of the currents I_2x, I_2y (see Figures 3 and 4) circulating in the resistive touch screen 1 as a result of two touch inputs PI, P2.

The overall magnification factor cmrent can be defined for both the axis 2C (defined as Kcunen ) ^me axis 2D (defined as Kcunent_j), i.e. for x axes and y axes respectively.

Particularly, the method obtains the overall magnification factor Kcunent and hence the modulation factor Kobject by:

- detecting, at a first time tl, a first value of current I_¾ circulating in said first layer 2 A when the latter is powered with said preset voltage value Vcc while said first layer 2A is being touched at said first point P 1 or at two points P 1 and P2;

- subtracting a first threshold value Ithdx from said first current value I_2x to generate a first processed current value I_2x,ti at said first time tl ;

- detecting, at a first time £2 (with t2 > tl), a second value of current I_2x> circulating in said first layer 2A when the latter is powered with said preset voltage value Vcc while said first layer 2A is being touched at said first point PI or at two points PI and P2;

- subtracting said first threshold value Ithdx from said second current value I_2x' to generate a second processed current value I_2x?t2 at said second time t2;

- defining a first magnification factor Kcmrenu along a first reference axis x using the formula

_ (Jlxfl ~ ^2x,tl )

current, x τ

¹2x,t\

Similar results are reached by the method when it obtains the factor Kamenty along a second reference axis 2D (i.e. the y axis) perpendicular to the first reference axis 2C (i.e. the x axis), using the formula:

2yj2

K, current, y

^L 2yA

- where :

- I_2x>tl and I_2y,ti designate the currents as measured in the screen 2A and the layer 2B at the time tl respectively, with the threshold values Ithdx and Ithdy subtracted therefrom respectively (see Figures 3 and 4) and

- I_2Xjt2 and I_2y,t2 designate the currents as measured in the screen 2A and the layer 2B at the time t2 respectively, with the threshold values Ithdx and

subtracted therefrom respectively (see Figures 3 and 4).

It shall be noted that the current value I^dx is a predetermined value that is preferably equal to the value of the current that circulates in the first powered layer 2A, when such first layer 2A is touched at one point only.

Finally, the overall magnification factor Kcmrcnt of the displayed object can be calculated using the following formula:

K current

^Λ cc.u., rrent,

Once the overall magnification factor

has been found, the object, i.e. the text, image, vector figure on the screen may be magnified or reduced by modulating such magnification or reduction using the modulation factor μ. Particularly, the modulation parameter μ modulates the overall object magnification factor Kcun-ent in proportion (at least at first) to the distance between said two touch points P1,P2 to define the modulation factor Kobject-

Therefore, this modulation parameter [ευ μ allows, for instance, the magnification of the object displayed along the y and y axes to be changed according to the distance that has been covered when ^"dragging the two touch points PI and P2, which means that the farther the distance created between PI and P2 when dragging the zoom (i.e. opening the fingers apart while touching the touch screen) the greater the magnification of the object.

In other words, the user can change the object magnification factor as desired, by changing the distance covered during the gestures operation, i.e. by a short expansion of the initial distance between the two touch points PI and P2 (e.g._small magnification) or a long expansion of the initial distance between the two touch points PI and P2 (e.g. great magnification).

It shall be also noted that, in addition to modulating the overall magnification factor Kobject in proportion to the distance between said two touch points PI, P2, the modulation parameter μ can modulate such modulation factor Kobject as a function of the rate of change of current I2x and/or I2y possibly with the formula: = u((^l2*-^{,2 ~ l2x}-^{n 2y}'^{t2 ~ l2y}-ⁿ )

μ^μ n - ti ^M n - t\ ^}

or with the formula:

AK

μ t2-t\

Particularly, the modulation parameter ts2 ] μ changes the modulation factor Kobject also considering the speed at which the two touch points PI and P2 move on the screen.

For instance, if the two touch points PI and P2 move apart from each other at a high speed, then the modulation factor Kobject will be higher and the object will be magnified by a higher factor as compared with the proportional value. .

In other words the modulation parameter μ may be defined as the sum of a parameter Up indicative of the proportionality and a parameter u_v indicative of the change of speed between the two touch points, i.e.

μ = μρ + μ_ν

It shall be noted that a first modified view X_sc and a second modified view Y_sc of the object along the first axis 2C and the second axis 2D of the screen may be defined using the following formulas:

^ X sc = ^ Kobj ct * W " object

Y sc = K object * T-f object

where W₀bj_ect and Hobjea designate the native width and height (in pixels) respectively of said object displayed on the resistive touch screen.

US2009/0322700 cannot account for either the distance between the two touch points or the speed at which the two touch points PI and P2 move apart from each other, as it only teaches qualitative evaluation of the change of current that flows into the layer once the screen has been touched at two points.

In other words, this document only teaches how to detect current changes, and does not mention any quantitative use of such information. Therefore, such document US2009/0322700 only teaches how to magnify or reduce the displayed image, and not how to modulate such magnification or reduction in response to user gestures on the screen.

Rotation

Advantageously, the measure of the angle 6_current between the orthogonal current components I_2x, I_2y may be related to a rotation factor θ₀¾_ε« of an object as it appears on the screen (text, image, vector figure, etc.) in a relative or absolute manner.

Particularly, if the angle 9_current between the orthogonal current components I_2x, I_2y is defined as:

and its variation A9_cmTent is defined as:

then the rotation factor 9₀bj_ect can be defined in an absolute manner, using the following formula:

^ ? - 5¹ B ^object = Λ y * θ ^w current

and in a relative manner, using the following formula:

object % current

where X is a constant parameter or depends on the rate of increase of current, according to the following relation:

where M _y = l ₂ - I_2y and AI_2x = I_{7x l2} - I_{2x tl}

or on the rate of increase of the angle, according to the following relation:

y _ γί __corrente_

z^x a -ti ⁾

As clearly shown in the above description, the method of the present invention fulfills the above mentioned need and also obviates prior art drawbacks as set out in the introduction of this disclosure.

Those skilled in the art will obviously appreciate that a number of changes and variants may be made to the above method, still within the scope of the invention, as defined in the following claims.

Claims

1 . A method of interpreting gestures on a resistive touch screen, such screen being designed to display an object and having a first layer (2A) and a second layer (2B) with a first axis (2C) and a second axis (2D) orthogonal to each other, being definable thereat, and wherein said first layer (2A) is designed to be touched, the method including the steps of:

- touching the first layer (2A) at two points (PI, P2);

- powering said first layer (2A) with a predetermined voltage value (Vcc), while said first layer (2A) is being touched at said points (PI, P2);

- detecting, at a first time (tl), a first value of current (I_2x) and a third value of current (I_2y) circulating in said first layer (2 A) and subtracting a first threshold value (Ithdx) from said first current value (I_2x) to generate a first processed current value (I₂x,ti) and subtracting a second threshold value (Ithdy) from said third current value (I_2y) to generate a third processed current value (I_2y,ti);

- detecting, at a second time (t2), a second value of current (Ι_2χ·) and a fourth value of current (I₂ ) circulating in said first layer (2A) and subtracting said first threshold value (Ithdx) from said second current value (Ι_2χ·) to generate a second processed current value (I_2Xit2) and subtracting said second threshold value (Ithdy) from said fourth current value (I₂ ) to generate a fourth processed current value (I_2y>tl);

- defining a first magnification factor (Kcun-en ) °f ^sa^ object along said first axis (2C) using the following formula:

^2x,t2 ~ ^2x,tl )

K current,x j

2x,t\

- defining a second magnification factor (Kcun-enty) of said object along said second axis (2D) perpendicular to said first reference axis, using the following formula: current, y

- defining an overall magnification factor (IQunent) of said object using the following formula:

'2

current,

said method being characterized in that it comprises the step of defining a modulation factor (Xobject) of said object on said screen, which is proportional to the distance between said two touch points (PI, P2) using the following formula:

K object = r a* * K current wherein μ designates a modulation parameter indicative of said distance between said two touch points (PI, P2), Kc_urreilt designating said overall magnification factor and Kobject designating said modulation factor.

2. A method of interpreting gestures as claimed in claim 1, comprising the step of modulating said modulation factor (Kobject) to define a first modified view (X_sc) and a second modified view (Y_sc) of said object along said first axis (2C) and said second axis (2D) respectively, using the following formulas:

X sc - *w

" object

Y sc = K object * M object

where X_sc designates said first modified view of said object, Y_sc designates said second modified view of said object, W₀bject and H₀bject designate the native width and height respectively of said object displayed on the resistive touch screen.

3. A method of interpreting gestures as claimed in claim 2, wherein said step of modulating said modulation factor (Kobject) is a function of the rate of change of said first current value (I_2x) and/or said second current value (I_2y), according to the following formula: μ /A{ _t2 _ _fl M _t2 _ _tl )

where:

- I2x,ti is said first processed current value, hx,a s said processed current value, I_{2y t}i is said third processed current value and I_2yjt2 is said fourth processed current value

- tl designates said first time and t2 designates said second time.

4. A method of interpreting gestures as claimed in claim 1, wherein instead of or in combination with the. step of defining said first magnification factor (Kcurren ) along a first reference axis (2C), said method includes the step of defining a rotation factor (9₀bj_ect) using the following formula:

Θ = Y * f)

"object A ^wci

where

χ being a constant parameter or depending on the rate of increase of current, according to the following relation:

where:

- xfl is said first processed current value, I_2x>t2 is said second processed current value, l2_y,ti is said third processed current value and I_2y>t2 is said fourth processed current value

■ tl designates said first time and t2 designates said second time.

5. A method of interpreting gestures as claimed in claim 1, wherein instead of defining a first magnification factor (K_CUrrent,x) along a first reference axis (2C), it includes the step of defining a rotation factor ( Δ 0_Object) using the following formula:

ΑΘ. oggetto χ* Αθ_ί

where _L

Δ0„

χ being a parameter that depends on the rate of increase of the angle, according to the following relation: z = x⁽- -)

t2 - t\