Method and device for controlling a touch screen

Abstract

The present invention relates to a method for controlling a touch screen comprising a display configured to display at least one graphical-interface element with a first graphical resolution, and a touch surface comprising a plurality of detection zones forming a detection grid the touch resolution of which is lower than the first resolution, the method being such that it comprises steps of determining (401) a display position of a graphical-interface element on the display such that the number of detection zones covered by said graphical-interface element is minimal, displaying (403) the graphical-interface element at the determined position and triggering (405) a function associated with the graphical-interface element when contact is detected (404) in a detection zone covered by the graphical-interface element. Other aspects of the invention relate to a device for implementing such a method and to a touch screen comprising the device.

Description

[0001] Method and device for controlling a touch screen

[0002] Technical field

[0003] The invention belongs to the field of touch screens and relates in particular to a method for improving the ergonomics of large touch screens.

[0004] Prior art

[0005] Touch interfaces are among the most common means of interaction on electronic devices. They are found on mobile devices such as smartphones, game consoles, ATMs, car entertainment devices, and laptops. Such interfaces allow for highly intuitive interaction with these devices by combining display and pointing functions.

[0006] A touchscreen generally comprises a display, for example an OLED or LCD screen, above which is arranged a transparent detection surface making it possible to determine the position of one or more contact points on the screen. Thus, the position of a contact detected on the touchscreen surface can be linked to a particular graphic object displayed on the screen to trigger a functionality associated with this graphic object.

[0007] Today, there are two main touchscreen technologies: resistive screens and capacitive screens.

[0008] Resistive screens are configured to detect pressure at a specific location. A resistive touch surface typically consists of three layers: a first, flexible protective layer positioned above two layers of conductive materials. When pressure is applied to the screen, the conductive materials are compressed and an electrical contact is created between the two surfaces. This electrical contact is detected and interpreted by a device to determine the location of the pressure from a voltage measurement at the contact point. This technology allows for high accuracy in determining the coordinates of the contact point.

[0009] Capacitive screens operate by touching, not pressing. They consist of a glass panel with an electrically charged conductive grid running through it. When a conductive object, such as a finger or a suitable stylus, comes into contact with the glass panel, the electric field at the point of contact is altered. The device determines the position of one or more contact points by evaluating the changes in the electric field using a mesh of electrodes.

[0010] As can be seen in Figure 1 a, a capacitive touch surface is made up of sensors arranged in columns A, B, C on a first layer and in lines 1, 2, 3 on a second layer, so as to obtain a detection grid. The columns A, B, C shown in Figure 1 a are for example negatively charged so as to create an electric field at the intersection points. When contact is made with a conductive material, such as a finger, the electric field is locally modified as shown in Figure 1 b. It is possible to measure this modification of the electric field to determine the location of the contact. The measurements are carried out by regularly scanning the columns one by one. Although the columns are scanned at a high frequency, this mechanism induces a delay between the instant of contact and the instant of its detection.This delay increases with the resolution of the sensor grid and can become noticeable on very large touchscreens. In the remainder of this description, the term "touch resolution" will be used to refer to the smallest difference in position that a touch surface is likely to detect during contact.

[0011] For example, while a conventional touchscreen with 80 rows and 40 columns offers a good compromise in terms of delay and precision when used on a smartphone, such a resolution may prove insufficient on a large screen. The lack of precision can lead to pointing errors and deteriorate the user experience. A similar problem occurs if, for economic reasons, a very low-resolution touchscreen is chosen on a modest-sized screen.

[0012] Figure 2a shows a touch screen adapted to display a graphical interface element at a particular location. For example, a button BT 1 of dimensions (w,h) is displayed at coordinates (x,y). These coordinates are relative to the graphical resolution of the display. In Figure 2a, a grid 200a is also shown comprising 18 columns and 16 rows which correspond to the sensor mesh of the touch surface and form a plurality of cells and whose resolution is that of the touch panel of the screen, each cell corresponding in the figure to a detection zone. The touch screen of Figure 2a is thus adapted to detect 18x16 different contact locations.

[0013] The screen of Figure 2a is associated with a processor configured by program instructions to determine, when a contact is detected in a particular cell of the touchpad at a particular location, whether to activate the functionality associated with an action on the button BT1. In other words, the program is configured to detect a pointing action on the button BT1, this detection comprising a conversion of the coordinates of the contact point detected by the touchpad into graphical coordinates, and a comparison of the coordinates of the contact point with the position and dimensions of the button BT1. Reference 201a designates the set of locations detectable by the touchpad which are associated with the button BT1. As seen in Figure 2a, the difference in resolution between the touchpad and the display introduces inaccuracies in the definition of the detection zone associated with the button BT1.In this example, we chose to associate a cell with the BT1 button as soon as at least one pixel of the button is included in this cell, so that the effective detection zone is larger than the button itself.

[0014] This inaccuracy becomes particularly problematic when the resolution of the touchscreen becomes much lower than the graphic resolution of the display. Figure 2b shows for example a screen similar to that of Figure 2a, but in which the touchscreen has a resolution twice lower than the screen of Figure 2a. It can be seen that the touch area 201b formed by the cells comprising at least one pixel of the button BT2 is much larger than the area 201a referenced in Figure 2a, even though the button BT2 is displayed in the same location with the same dimensions as the button BT1 of Figure 2a. Consequently, the button BT2 can be selected by pointing at pixels that do not belong to the button BT2, for example by touching the screen at the location of cells D2 to D5.In addition to the problem of imprecision when selecting button BT2, having detection areas larger than the graphical objects poses a problem when several interactive objects are displayed at a short distance. For example, there is ambiguity regarding which button BT2 or BT3 should be activated when touching one of the cells D2 to D5 shown in Figure 2b because cells D2 to D5 include at least one pixel of each of these buttons. To avoid this kind of situation, one can arbitrarily decide to associate a touch area with a single graphical element in case of ambiguity, but this can also lead to confusion. For example, associating cells D2 to D5 exclusively with button BT2 limits the interaction area associated with button BT3, to the point that pointing at the bottom of button BT2 will be interpreted as pointing at button BT3.

[0015] Thus, ergonomic problems arise when the resolution of the touch surface is much lower than the graphic resolution of the display.

[0016] There is therefore a need for a solution to improve the user experience when using a touch screen comprising a touch panel whose touch resolution is particularly low compared to the graphic resolution of the display.

[0017] Summary of the invention

[0018] To this end, a method is proposed for controlling a touch screen comprising a display adapted to display at least one graphical interface element with a first graphical resolution, and a touch surface comprising a plurality of detection zones forming a detection grid whose touch resolution is lower than the first resolution, the method being such that it comprises steps of:

[0019] - Determining a display position of a graphical interface element on the display such that the number of detection zones covered by said graphical interface element is minimal,

[0020] - Displaying the GUI element at the determined position, and

[0021] - Triggering a function associated with the graphical interface element when a contact is detected in a detection zone covered by the graphical interface element. The method thus makes it possible to improve the precision of a touch screen during pointing operations, in particular when the resolution of the touch panel is significantly lower than the graphical resolution of the display. More precisely, by calculating the position of an interactive object displayed on the screen so that this object occupies a minimum of detection zones, the extent of the touch zone around the graphical object is limited. Consequently, selection errors are reduced. The method is particularly advantageous when applied to large touch screens where the aim is to control the cost at the expense of the precision of the touch panel, the difference between the touch resolution and the graphical resolution then being particularly significant.

[0022] According to a particular embodiment, the method is such that the step of determining a position of a graphical interface element comprises determining a display position of said interface element such that at least one border of the interface element is aligned with a border of a detection zone.

[0023] It is thus proposed to adjust the position of a graphic element so that at least one of its edges coincides with a boundary delimiting two adjacent detection zones. In this way, it is prevented that a pointing action carried out near the graphic element is interpreted as a pointing of this element. The user experience is thus improved.

[0024] According to a particular embodiment, the method is such that the step of determining the position of a graphical interface element comprises determining a display position of the graphical interface element such that at least two consecutive edges of the graphical interface element are respectively aligned with at least two borders of a detection zone.

[0025] Such an arrangement makes it possible to match the graphical interface element even better with the sensor mesh of the touch screen, so that ergonomics is improved. According to a particular embodiment, the method is such that it further comprises the following steps:

[0026] - determining at least one dimension of the graphical interface element such that the interface element covers an integer number of detection zones according to said dimension,

[0027] - resizing the GUI element according to the determined dimension.

[0028] It is thus proposed to adapt a dimension of the GUI element to fit the resolution of the touchscreen. For example, the length or width of a button is adjusted to cover an integer number of detection zones. In other words, the dimension is adjusted to match the granularity of the touch surface, i.e. at least two opposite edges of the GUI element are aligned with the detection grid.

[0029] According to another aspect, there is provided a device for controlling a touch screen comprising a display adapted to display at least one graphical interface element with a first graphical resolution, and a touch surface comprising a plurality of detection zones forming a detection grid whose resolution is lower than the first resolution, the device further comprising a processor coupled to a memory in which computer program instructions are recorded configured to implement the following steps:

[0030] - determining a display position of a graphical interface element on the display such that the number of detection zones covered by said graphical interface element is minimal,

[0031] - displaying the GUI element at the determined position, and

[0032] - Triggering a function associated with the graphical interface element when a contact is detected in a detection zone covered by the graphical interface element. According to a particular embodiment, the device is such that the program instructions stored in the memory are further configured to:

[0033] - determining at least one dimension of the graphical interface element such that the interface element covers an integer number of detection zones according to said dimension,

[0034] - resize the GUI element according to the determined dimension.

[0035] The invention also relates to a touch screen comprising a device as described above.

[0036] Finally, the invention relates to an information medium comprising computer program instructions configured to implement the steps of a method for controlling a touch screen as described previously, when the instructions are executed by a processor.

[0037] The information medium may be a non-transitory information medium such as a hard disk, flash memory, or an optical disk for example.

[0038] The information carrier can be any entity or device capable of storing instructions. For example, the carrier may include a storage medium, such as a ROM (Read Only Memory), RAM (Random Access Memory), PROM (Programmable Read Only Memory), EPROM (Eraseable Programmable Read Only Memory), a CD-ROM or a magnetic recording medium, for example a hard disk.

[0039] On the other hand, the information carrier may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means.

[0040] Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the methods in question. The various embodiments or features mentioned above may be added independently or in combination with each other, to the steps of the control method.

[0041] The methods, devices, touch screens and information media have at least advantages similar to those conferred by the method to which they relate.

[0042] Brief description of the figures

[0043] Other characteristics and advantages of the invention will become apparent from reading the description which follows. This description is purely illustrative and must be read in conjunction with the appended drawings in which:

[0044] - Figure 1a shows an example of a mesh of electrodes of a capacitive touch screen in the absence of tactile contact,

[0045] - Figure 1 b shows an example of a mesh of electrodes of a capacitive touch screen during a tactile contact,

[0046] - Figure 2a shows a button displayed on a touch screen adapted to detect contacts with a first resolution,

[0047] - Figure 2b shows two buttons displayed on a touch screen adapted to detect contacts with a second resolution,

[0048] - Figure 3a shows a touch screen on which a button is displayed in a first location,

[0049] - figure 3b shows a touch screen on which a button is displayed, repositioned according to a particular embodiment,

[0050] - figure 3c shows a touch screen on which a button is displayed, repositioned according to a particular embodiment,

[0051] - figure 3d shows a touch screen on which a resized button is displayed according to a particular embodiment,

[0052] - figure 4 is a flowchart showing the main steps of a control method according to a particular embodiment,

[0053] - Figure 5 schematically represents the architecture of a device suitable for implementing the control method according to a particular embodiment. Detailed description

[0054] Figure 3a shows a touch screen 300 on which a BT button is displayed. The screen 300 is for example integrated into a tablet, a computer, an ATM, a game console or even an automobile entertainment device.

[0055] The touch screen comprises a display, for example an LCD or OLED screen, or a cathode ray tube screen, and a transparent touch surface allowing a user to select a graphic object by touching the screen 300 at the location of the graphic object.

[0056] The display is suitable for displaying graphic objects with a particular graphic resolution. The screen 300 thus makes it possible, for example, to display a BT button at the coordinates (x1, y1). The BT button is a graphical interface element of width w1 pixels and height h1 pixels which is configured to trigger a particular action when it is pointed at by the user through the touch surface. Various technologies can be used to implement the touch surface. For example, it can be a capacitive or resistive surface. Whatever the technology chosen, the touch surface has a particular tactile resolution imposed by the mesh of detectors. Here, tactile resolution is understood to mean the smallest difference in position that a touch surface is capable of detecting during contact.The term "detection zone" will be used to designate a set of locations on the touch surface at which contacts are interpreted as having the same position due to the touch resolution. Generally, the touch resolution is lower than the graphic resolution. Figure 3a shows a grid to materialize the touch resolution of the screen 300. Thus, in this example, the resolution of the touch surface is much lower than the graphic resolution of the display. The cells defined by the grid represent detection zones within which it is not possible to distinguish different contact positions.

[0057] Because the resolution of the touch surface is different from the graphic resolution of the display, the touch screen 300 includes a processing unit configured to convert the coordinates of a contact detected on the touch surface into display coordinates. In practice, when a contact is detected on the touch surface at a particular location, the processing unit associated with the screen 300 determines the pixel or pixels of the display that have been pointed at by the user. For this, the processing unit obtains the resolution of the touch surface and the resolution of the display and calculates a ratio to determine a set of pixels corresponding to the detection area touched by the user. Thus, when for example a contact is detected on the screen 300 in the detection area D5, the processing unit determines that all the pixels of the display included in the area D5 are selected.

[0058] Conventionally, the BT button, like all interactive graphic objects that can be displayed on such a screen, is associated with an activation region configured in such a way that a user pointing in this region is interpreted as an action on the button and triggers an associated function. The activation region associated with the BT button is for example defined by the pixels that contribute to the graphical representation of this button. In other examples, such as in the case of hypertext links, the activation region can be defined independently of the pixels, for example by means of a rectangular area defined by coordinates.

[0059] As shown in Figure 3a, the detection area D5 includes a part of the BT button, so that a user pointing anywhere in the detection area D5 is interpreted as a selection of the BT button. There is therefore a risk that a user action in one of the detection areas 301 will be mistakenly interpreted as a selection of the BT button.

[0060] In order to improve pointing accuracy, the present invention proposes adjusting the position and dimensions of a graphical interface element so as to reduce the inaccuracy resulting from the difference in resolution between the touch surface and the display.

[0061] A particular embodiment of a method for controlling a touch screen will now be described with reference to Figure 4.

[0062] Figure 4 is a flowchart illustrating the main steps of a method for controlling a touch screen according to a particular embodiment.

[0063] The method is for example implemented by a control device comprising a processor coupled to a memory in which computer program instructions are recorded suitable for implementing the steps of the control method when they are executed by the processor.

[0064] In a first step 400, the device obtains the touch resolution of the touch surface and the graphic resolution of the display of a touch screen such as the screen 300 described above. The resolution values ​​are for example preconfigured in a ROM which the processor can access, in a configuration file of an operating system of a device in which the screen is integrated or even from a device driver software associated with the screen. From the resolutions thus obtained, the device calculates a ratio between the graphic resolution and the touch resolution, in order to determine the dimensions, in pixels, of a touch detection zone.

[0065] In step 401, the device determines a display position of a graphical interface element on the display such that the number of detection zones covered by said graphical interface element is minimal. For this, the device obtains the position of a graphical interface element such as the BT button shown in FIG. 3a. The position of the BT button corresponds for example to the coordinates of the upper left corner, but any other anchor point can be envisaged without modifying the invention. Thus, the BT button shown in FIG. 3a is positioned at the graphical coordinates (x1, y1). The device then determines a new position of the BT button such that at least one border of the interface element is aligned with a border of a detection zone. For this, the device can calculate a quotient from the abscissa x1 of the BT button and the width, in pixels, of a touch detection zone.In this way, the device can obtain a new abscissa of the BT button which is aligned with the mesh of the touch surface. Figure 3b shows the screen 300 of Figure 3a after modifying the position of the BT button along the abscissa axis. The left edge of the BT button is then aligned with a detection zone border of the touch surface. In this example, the horizontal displacement of the BT button makes it possible to limit the number of detection zones 301 of the touch surface likely to activate the BT button.

[0066] In a particular embodiment, the device calculates a quotient from the ordinate y1 of the BT button and the height, in pixels, of a touch detection zone determined in step 400. In this way, the device can obtain a new ordinate of the BT button which is aligned with the mesh of the touch surface. Figure 3c shows the screen 300 of Figure 3b after modification of the position of the BT button along the ordinate axis. The upper edge of the BT button is then aligned with a detection zone border of the touch surface. In this example, the vertical displacement of the BT button makes it possible to further limit the number of detection zones 301 of the touch surface capable of activating the BT button.

[0067] In an optional step 402, the device may adjust at least one dimension of the BT button, for example its width w1 and / or its height h1. More precisely, the device determines at least one dimension of the BT button such that an integer number of detection zones is covered by the interface element according to said at least one dimension. In other words, the height and / or the width of the BT button is adjusted so that two opposite edges are aligned on a detection zone boundary, preferably the closest boundaries. Figure 3d illustrates such a situation: the width w2 of the BT button of Figure 3c is adjusted to align the right edge of the BT button on the boundary between the detection zones C4 and C5.

[0068] The method comprises a step 403 during which the graphical interface element BT is displayed on the display of the touch screen 300 according to the position and dimensions determined during steps 401 and 402. Thanks to the method implemented, the number of detection zones covered by the BT button is optimal: while at the initial location, represented in FIG. 3a the BT button covers 8 detection zones of the touch surface, it occupies exactly 3 detection zones after repositioning and resizing. The pointing accuracy and the user experience are thus improved.

[0069] The method finally comprises a step 404, during which the device detects a pointing of the user on the BT button, i.e. a contact on the touch surface in a detection zone which is covered by the BT graphical interface element, and triggers a function associated with the graphical interface element.

[0070] Figure 5 represents the architecture of a control device 500 adapted to implement the method of controlling a touch screen according to a particular embodiment.

[0071] The device 500 comprises a storage space 502, for example a memory MEM, a processing unit 501 equipped for example with a processor PROC. The processing unit can be controlled by a program 503, for example a computer program PGR, implementing the control method described with reference to FIG. 4 and in particular the steps of determining a display position of a graphical interface element on the display such that the number of detection zones covered by said graphical interface element is minimal, of displaying the graphical interface element at the determined position and of triggering a function associated with the graphical interface element when a contact is detected in a detection zone covered by the graphical interface element.

[0072] Upon initialization, the instructions of the computer program 503 are for example loaded into a RAM (Random Access Memory) memory before being executed by the processor of the processing unit 501. The processor of the processing unit 501 implements the steps of the control method according to the instructions of the computer program 503.

[0073] The device 500 comprises a display 504, for example an LCD or OLED screen, adapted to display graphic objects with a particular graphic resolution, above which is arranged a touch surface 505 adapted to determine coordinates of one or more locations pointed by a user, using a finger or a stylus for example. The touch surface is for example a capacitive or resistive DSP panel comprising a mesh of sensors making it possible to determine the position of a contact with a particular touch resolution, lower than the graphic resolution of the display 504, the sensor mesh defining a plurality of contact detection zones. The touch surface 505 is superimposed on the screen 504 to form a touch screen from which a user can control the device 500.

[0074] The device 500 comprises a module 506 for repositioning a graphical interface element adapted to determine a display position of said graphical interface element on the display such that the number of contact detection zones covered by said graphical interface element is minimal. The module 506 can be implemented by POS computer program instructions configured to calculate a ratio between the resolution of the display 504 and the touch resolution of the touch surface 505 and to determine at least one position of the interface element such that the distance, in pixels, between an edge of the screen and an edge of the interface element is a multiple of the distance, in pixels, between the opposite edges of a detection zone.

[0075] In a particular embodiment, the device 500 may also comprise a module 507 for resizing a graphical interface element adapted to determine at least one dimension of said graphical interface element on the display such that said graphical interface element covers an integer number of detection zones according to said dimension. The module 507 is for example implemented by SZE program instructions configured to enlarge or reduce a dimension of the interface element so that this dimension, in pixels, is a multiple of the dimension, in pixels, of a touch detection zone.

[0076] The display 504 is further configured to display a graphical interface element at the position determined by the repositioning module 506, and according to the dimensions determined by the resizing module 507.

[0077] Finally, the computer program 503 includes instructions configured to trigger execution of a function associated with the graphical interface element when contact is detected in a detection area covered by the repositioned and resized graphical interface element.

[0078] According to a particular embodiment, the device 500 is integrated into a tablet, a smartphone, a laptop, a game console, a machine tool, an access controller, an ATM or even an automotive entertainment device.

Claims

CLAIMS 1. Method for controlling a touch screen comprising a display adapted to display at least one graphical interface element with a first graphical resolution, and a touch surface comprising a plurality of detection zones forming a detection grid whose touch resolution is lower than the first resolution, the method being such that it comprises steps of: - Determination (401) of a display position of a graphical interface element on the display such that the number of detection zones covered by said graphical interface element is minimal, - Display (403) of the graphical interface element at the determined position. - Triggering (405) a function associated with the graphical interface element when a contact is detected (404) in a detection zone covered by the graphical interface element.

2. Method according to claim 1 wherein the step of determining a position of a graphical interface element comprises determining a display position of said interface element such that at least one border of the interface element is aligned with a border of a detection zone.

3. The method of claim 1 wherein the step of determining the position of a graphical interface element comprises determining a display position of the graphical interface element such that at least two consecutive edges of the graphical interface element are respectively aligned with at least two borders of a detection zone.

4. Method according to any one of the preceding claims such that it further comprises the following steps: - Determining at least one dimension of the graphical interface element such that the interface element covers an integer number of detection zones according to said dimension, - Resizing the GUI element according to the determined dimension. Device for controlling a touch screen comprising a display (504) adapted to display at least one graphical interface element with a first graphical resolution, and a touch surface (505) comprising a plurality of detection zones forming a detection grid whose resolution is lower than the first resolution, the device further comprising a processor (501) coupled to a memory (502) in which computer program instructions (503) are recorded, configured to implement the following steps: - Determining a display position of a graphical interface element on the display such that the number of detection zones covered by said graphical interface element is minimal, - Displaying the GUI element at the determined position. - Triggering a function associated with the graphical interface element when a contact is detected in a detection zone covered by the graphical interface element. Touch screen comprising a control device according to claim 5. Information medium comprising computer program instructions configured to implement the steps of a method for controlling a touch screen according to any one of claims 1 to 4, when the instructions are executed by a processor.

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