Method and apparatus for controlling touch screen

Abstract

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

Description

Technical Field

[0001] The present invention relates to the field of touch screens, and in particular to a method for improving the ergonomics of large touch screens. Background Art

[0002] Touch interfaces are one of the most common ways of interacting with electronic devices. These touch interfaces can be used in mobile terminals such as smartphones, game consoles, ATMs, car entertainment devices or portable computers. Such interfaces are used to interact with these devices very intuitively by combining display and pointing functions.

[0003] A touch screen generally comprises a display, such as an OLED or LCD screen, above which a transparent detection surface is arranged for determining the position of one or more contact points on the screen. Thus, the contact position detected on the touch surface can be associated with a specific graphical object displayed on the screen in order to trigger a function associated with the graphical object.

[0004] Today, there are two main touchscreen technologies: resistive and capacitive.

[0005] Resistive screens are configured to detect pressure at specific locations. Resistive touch surfaces usually consist of 3 layers: a first flexible protective layer, which sits on top of two layers of conductive material. When pressure is applied to the screen, the conductive material is compressed and an electrical contact is created between the two surfaces. This electrical contact is detected and interpreted by the device to determine the point where the pressure was applied based on the voltage measurement at the point of contact. This technology enables the coordinates of the point of contact to be determined with high accuracy.

[0006] Capacitive screens operate by touch rather than pressure. A capacitive screen consists of a glass panel crossed by a grid of electrically charged electrodes. When a conductive object (such as a finger or a suitable stylus) comes into contact with the glass panel, the electric field changes at the location of the contact. The device determines the location of one or more contact points by evaluating the change in the electric field using the grid of electrodes.

[0007] As can be seen in FIG. 1a, a capacitive touch surface is made up of sensors arranged in columns A, B, C on a first layer and in rows 1, 2, 3 on a second layer, forming a detection grid. For example, columns A, B, C shown in FIG. 1a are negatively charged so that an electric field is generated at the intersection. When contact is made with a conductive material such as a finger, the electric field changes locally, as shown in FIG. 1b. This change in the electric field can be measured to determine the contact position. These measurements are made by scanning column by column at regular intervals. Despite the high frequency of crossing of these columns, this mechanism produces a delay between the moment of contact and the moment of detection of the contact. This delay increases with the resolution of the detection grid and can become noticeable on very large touch screens. In the remainder of this specification, the term "touch resolution" will be used to refer to the minimum position difference that a touch surface can detect during contact.

[0008] For example, a classic touch panel with 80 rows and 40 columns, when used on a smartphone, provides a good compromise between latency and accuracy, but this resolution may not be enough on a giant screen. Lack of accuracy may lead to pointing errors and reduce the user experience. The same problem occurs if, for economic reasons, you choose to use a touch panel with a very low resolution on a medium-sized screen.

[0009] Figure 2a shows a touch screen adapted to display a graphical interface element at a specific location. For example, a button BT1 of size (w, h) is displayed at coordinates (x, y). These coordinates are relative to the graphics resolution of the display.

[0010] FIG2a also shows a grid 200a including 18 columns and 16 rows, which corresponds to the sensor grid of the touch surface and forms a plurality of cells, and the resolution of the grid is the resolution of the touch panel of the screen, and each cell in the figure corresponds to a detection area. Therefore, the touch screen in FIG2a is adapted to detect 18×16 different contact positions.

[0011] The screen in Fig. 2a is associated with a processor, which is configured by program instructions to determine whether to activate a function associated with an action on button BT1 when contact of a specific cell on a specific position of the touch panel is detected. In other words, the program is configured to detect a pointing action associated with button BT1, and this detection includes converting the coordinates of the contact point detected by the touch panel into graphic coordinates, and comparing the coordinates of the contact point with the position and size of button BT1. Reference numeral 201a represents all positions associated with button BT1 that can be detected by the touch panel. As can be seen in Fig. 2a, the resolution difference between the touch panel and the display can cause inaccurate definition of the detection area associated with button BT1. In this example, when at least one pixel of the button is included in a cell, the cell is selected as being associated with button BT1, so the effective detection area is larger than the button itself.

[0012] This inaccuracy becomes particularly problematic when the resolution of the touch panel is much lower than the graphic resolution of the display. FIG. 2b shows, for example, a screen similar to that in FIG. 2a, but wherein the resolution of the touch panel is one-half of that in FIG. 2a. It can be seen that, although button BT2 is displayed in the same position and of the same size as button BT1 of FIG. 2a, the touch area 201b formed by the cell including at least one pixel of button BT2 is much larger than the area 201a referenced in FIG. 2a. Therefore, button BT2 may be selected by pointing to a pixel that does not belong to button BT2, for example, by touching the screen at the position of cells D2 to D5. In addition to the problem of inaccuracy when selecting button BT2, problems may arise when the detection area is larger than the graphic object when multiple interactive objects are displayed at a short distance. For example, in the case of contact with one of the cells D2 to D5 shown in FIG. 2b, it is unclear which of these buttons needs to be activated because cells D2 to D5 include at least one pixel of each of buttons BT2 or BT3. To avoid this, it can be arbitrarily decided to associate a touch area with a single graphic element in the case of ambiguity, but this may also cause confusion. For example, associating all of cells D2 to D5 with button BT2 would restrict the interactive area associated with button BT3 so that a point pointing to the bottom of button BT2 would be interpreted as pointing to button BT3.

[0013] Therefore, ergonomic issues arise when the resolution of the touch surface is much lower than the graphics resolution of the display.

[0014] Therefore, a solution is needed to improve the user experience when using a touch screen including a touch panel whose touch resolution is particularly low compared to the graphics resolution of the display. Summary of the invention

[0015] To this end, a method for controlling a touch screen is proposed, the touch screen comprising: a display adapted to display at least one graphical interface element at a first graphics resolution; and a touch surface comprising a plurality of detection areas forming a detection grid, the touch resolution of the detection grid being lower than the first resolution, the method comprising the following steps:

[0016] - determining a display position of a graphical interface element on the display so that the amount of the detection area covered by the graphical interface element is minimized,

[0017] - displaying the graphical interface element at the determined position, and

[0018] - When a contact is detected in a detection area covered by the graphical interface element, a function associated with the graphical interface element is triggered.

[0019] Thus, the method improves the accuracy of the touch screen during pointing operations, especially when the resolution of the touch panel is significantly lower than the graphic resolution of the display. More precisely, the position of the interactive object displayed on the screen is calculated so that the detection area occupied by the object is minimized, thereby limiting the extent of the touch area around the graphic object. As a result, selection errors are reduced. This method is particularly advantageous when applied to large touch screens, because the need to control the cost of these large touch screens affects the accuracy of the touch panel, so that the difference between the touch resolution and the graphic resolution is particularly large.

[0020] According to a specific embodiment, the method is such that the step of determining the position of the graphical interface element comprises determining the display position of said interface element such that at least one boundary of the interface element is aligned with a boundary of the detection area.

[0021] It is therefore proposed to adjust the position of the graphic element so that at least one of its edges coincides with the boundary defining two adjacent detection areas. In this way, a pointing action performed near the graphic element is prevented from being interpreted as pointing to the element. This improves the user experience.

[0022] According to a specific embodiment, the method makes the step of determining the position of the graphical interface element include determining the display position of the graphical interface element so that at least two continuous edges of the graphical interface element are respectively aligned with at least two boundaries of the detection area.

[0023] This arrangement even better matches the graphical interface elements with the grid of the touch panel's detectors, resulting in improved ergonomics.

[0024] According to a particular embodiment, the method is such that it further comprises the following steps:

[0025] - determining at least one size of the graphical interface element so that the interface element covers an integer number of detection areas according to the size,

[0026] -Adjusting the size of the graphical interface element according to the determined size.

[0027] It is therefore proposed that the size of the graphical interface element is adapted to adjust it to the resolution of the touch panel. For example, the length or width of a button is adjusted to cover an integer number of detection areas. In other words, the size is adjusted to match the granularity of the touch surface, that is, at least two opposite edges of the graphical interface element are aligned with the detection grid.

[0028] According to another aspect, a device for controlling a touch screen is provided, the touch screen comprising: a display adapted to display at least one graphical interface element at a first graphics resolution; and a touch surface comprising a plurality of detection areas forming a detection grid, the resolution of the detection grid being lower than the first resolution, the device further comprising a processor coupled to a memory storing computer program instructions configured to perform the following steps:

[0029] - determining a display position of a graphical interface element on the display so that the amount of the detection area covered by the graphical interface element is minimized,

[0030] - displaying the graphical interface element at the determined position, and

[0031] - When a contact is detected in a detection area covered by the graphical interface element, a function associated with the graphical interface element is triggered.

[0032] 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 size of the graphical interface element so that the interface element covers an integer number of detection areas according to the size,

[0034] -Adjusting the size of the graphical interface element according to the determined size.

[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 which are configured to perform the steps of the method for controlling a touch screen as described above when these instructions are executed by a processor.

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

[0038] The information medium may be any entity or device capable of storing instructions. For example, the medium may include a storage device such as a ROM (read-only memory), a RAM (random access memory), a PROM (programmable read-only memory), an EPROM (erasable programmable read-only memory), a CD ROM, or a magnetic recording device (e.g., a hard disk).

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

[0040] Alternatively, the information medium may be an integrated circuit containing the program, the circuit being adapted to carry out or to be used for carrying out the method in question.

[0041] The various embodiments or features mentioned above may be added to the steps of the control method independently or in combination with each other.

[0042] These methods, devices, touch screens and information media have at least similar advantages as those afforded by the methods to which they relate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other features and advantages of the present invention will become apparent from reading the following description. The present invention is purely illustrative and must be read in conjunction with the accompanying drawings, in which:

[0044] - FIG. 1 a shows an example of an electrode grid of a capacitive touch screen in the absence of a touch contact,

[0045] - Fig. 1b shows an example of an electrode grid of a capacitive touch screen during a touch contact,

[0046] - FIG. 2a shows a button displayed on a touch screen adapted to detect contacts at a first resolution,

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

[0048] - Fig. 3a shows a touch screen displaying a button in a first position,

[0049] - FIG. 3 b shows a touch screen displaying buttons repositioned according to certain embodiments,

[0050] - FIG. 3 c shows a touch screen displaying buttons repositioned according to certain embodiments,

[0051] - FIG. 3 d shows a touch screen displaying a button resized according to a particular embodiment,

[0052] - Figure 4is a flow chart showing the main steps of a control method according to a specific embodiment,

[0053] - Figure 5 The architecture of a device adapted to perform a control method according to a particular embodiment is schematically shown. DETAILED DESCRIPTION

[0054] Fig. 3a shows a touch screen 300 displaying a button BT. The screen 300 is for example integrated in a tablet, a computer, an ATM, a game console or an entertainment device for a car.

[0055] The touch screen includes a display (eg, an LCD or OLED screen), or a cathode ray screen, and a transparent touch surface, so that a user can select a graphic object by touching the position of the graphic object on the screen 300 .

[0056] The display is adapted to display graphic objects at a specific graphic resolution. Thus, the screen 300 allows, for example, the display of a button BT at coordinates (x1, y1). The button BT is a graphical interface element with a width of w1 pixels and a height of h1 pixels, which is configured to trigger a specific action when a user points to the button through a touch surface. The touch surface can be implemented using various technologies. For example, the touch surface can be a capacitive or resistive surface. Regardless of which technology is selected, the touch surface will have a specific touch resolution due to the grid of the detector. The touch resolution should be understood here to mean the minimum position difference that the touch surface can detect during contact. The term "detection area" will be used to represent a set of positions on the touch surface, and contacts at these positions are interpreted as having the same position due to the touch resolution. Typically, the touch resolution is lower than the graphic resolution. Figure 3a shows a grid that implements the touch resolution of the screen 300. Therefore, 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 areas, and different contact positions cannot be distinguished within these detection areas.

[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 the contact detected on the touch surface into display coordinates. In practice, when a contact is detected at a specific location on the touch surface, the processing unit associated with the screen 300 determines one or more pixels of the display pointed to by the user. To this end, 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, for example, when a contact is detected in the detection area D5 of the screen 300, the processing unit determines that all pixels of the display included in the area D5 are selected.

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

[0059] 3a, detection area D5 includes a portion of button BT, so a user pointing anywhere in detection area D5 is interpreted as selecting button BT. Therefore, there is a risk that a user's action in one of detection areas 301 is erroneously interpreted as selecting button BT.

[0060] In order to improve pointing accuracy, the present invention proposes to adjust the position and size of graphical interface elements in order to reduce the inaccuracy caused by the resolution difference between the touch surface and the display.

[0061] Now refer to Figure 4 Specific embodiments of a method for controlling a touch screen are described.

[0062] Figure 4 is a flow chart showing main steps of a method for controlling a touch screen according to a specific embodiment.

[0063] The method is for example performed by a control device comprising a processor coupled to a memory storing computer program instructions adapted to perform the steps of the control method when executed by the processor.

[0064] During a first step 400, the device obtains the touch resolution of the touch surface and the graphic resolution of the display of the touch screen (such as the screen 300 described above). For example, the resolution value is preconfigured in a ROM accessible to the processor, in a configuration file of the operating system of the device integrated with the screen, or in the device driver software associated with the screen. Based on the resolution thus obtained, the device calculates the ratio between the graphic resolution and the touch resolution in order to determine the size (in pixels) of the touch detection area.

[0065] In step 401, the device determines the display position of the graphical interface element on the display so that the number of detection areas covered by the graphical interface element is minimized. To this end, the device obtains the position of the graphical interface element (such as the button BT shown in Figure 3a). The position of the button BT corresponds to the coordinates of the upper left corner, for example, but any other anchor point can also be envisioned without modifying the present invention. Therefore, the button BT shown in Figure 3a is located at the graphic coordinates (x1, y1). Then, the device determines the new position of the button BT so that at least one boundary of the interface element is aligned with the boundary of the detection area. To this end, the device can calculate the quotient based on the x coordinate x1 of the button BT and the width (in pixels) of the touch detection area. In this way, the device can obtain the new x coordinate of the button BT aligned with the grid of the touch surface. Figure 3b shows the screen 300 of Figure 3a after the position of the button BT has been changed along the x-axis. Then the left edge of the button BT is aligned with the detection area boundary of the touch surface. In this example, the horizontal movement of the button BT allows the number of detection areas 301 on the touch surface that can activate the button BT to be limited.

[0066] In a particular embodiment, the device calculates a quotient based on the y coordinate y1 of the button BT and the height (in pixels) of the touch detection area determined in step 400. In this way, the device can obtain a new y coordinate of the button BT aligned with the grid of the touch surface. Figure 3c shows the screen 300 of Figure 3b after the position of the button BT has been changed along the y axis. The top edge of the button BT is then aligned with the detection area boundary of the touch surface. In this example, the vertical movement of the button BT allows to further limit the number of detection areas 301 on the touch surface that can activate the button BT.

[0067] During optional step 402, the device may adjust at least one dimension of the button BT, such as its width w1 and / or its height h1. More specifically, the device determines at least one dimension of the button BT so that the interface element covers an integer number of detection areas according to the at least one dimension. In other words, the height and / or width of the button BT is adjusted so that the two opposite edges are aligned with the detection area boundaries (preferably the nearest boundaries). Figure 3d shows this situation: the width w2 of the button BT of Figure 3c is adjusted so that the right edge of the button BT is aligned with the boundary between the detection areas C4 and C5.

[0068] The method comprises a step 403 during which a graphical interface element BT is displayed on the display of the touch screen 300 according to the position and size determined during steps 401 and 402. Due to the method performed, the number of detection areas covered by the button BT is optimal: in the initial position shown in FIG3 a , the button BT covers 8 detection areas of the touch surface, while after repositioning and resizing it occupies exactly 3 detection areas. This improves pointing accuracy and user experience.

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

[0070] Figure 5 The architecture of a control device 500 is shown, which is adapted to perform a method for controlling a touch screen according to certain embodiments.

[0071] The device 500 comprises a storage space 502, such as a memory MEM, a processing unit 501 equipped with, for example, a processor PROC. The processing unit may be driven by a program 503, such as a computer program PGR, which executes reference Figure 4 The control method described herein specifically performs the following steps: determining a display position of a graphical interface element on a display so that the amount of a detection area covered by the graphical interface element is minimized; displaying the graphical interface element at the determined position; and triggering a function associated with the graphical interface element when contact is detected in the detection area covered by the graphical interface element.

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

[0073] The device 500 includes a display 504, such as an LCD or OLED screen, which is adapted to display graphic objects at a specific graphic resolution, and a touch surface 505 is arranged above the display, which is adapted to determine the coordinates of one or more locations pointed to by a user using, for example, a finger or a stylus. The touch surface is, for example, a capacitive or resistive panel DSP, which includes a detector grid for determining the contact position at a specific touch resolution (lower than the graphic resolution of the display 504), and the sensor grid defines a plurality of contact detection areas. The touch surface 505 is superimposed on the screen 504 to form a touch screen through which the user can control the device 500.

[0074] Device 500 includes a module 506 for repositioning a graphical interface element, the graphical interface element being adapted to determine a display position of the graphical interface element on the display so that the amount of contact detection area covered by the graphical interface element is minimized. Module 506 may be implemented by computer program instructions POS configured to calculate a ratio between a resolution of display 504 and a touch resolution of touch surface 505, and to determine at least one position of the interface element so 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 opposite edges of the detection area.

[0075] In a particular embodiment, the device 500 may further include a module 507 for adjusting the size of a graphical interface element, the graphical interface element being adapted to determine at least one size of the graphical interface element on the display so that the graphical interface element covers an integer number of detection areas according to the size. The module 507 is implemented, for example, by program instructions SZE, which are configured to increase or decrease the size of the interface element so that the size (in pixels) is a multiple of the size (in pixels) of the touch detection area.

[0076] Display 504 is also configured to display the graphical interface element at the location determined by repositioning module 506 and according to the size determined by resizing module 507 .

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

[0078] According to one particular embodiment, the device 500 is integrated into a tablet computer, a smartphone, a portable computer, a game console, a machine tool, an access controller, an automated teller machine, or an entertainment device of a car.

Claims

1. A method for controlling a touch screen, the touch screen comprising: a display adapted to display at least one graphical interface element at a first graphics resolution; and a touch surface comprising a plurality of detection areas forming a detection grid, the touch resolution of the detection grid being lower than the first resolution, the method comprising the steps of: - determining (401) a display position of a graphical interface element on the display so that the amount of detection area covered by the graphical interface element is minimized, - displaying (403) the graphical interface element at the determined position, - When a contact is detected (404) in a detection area covered by the graphical interface element, a function associated with the graphical interface element is triggered (405).

2. The method of claim 1, wherein: The step of determining the position of the graphical interface element includes determining the display position of the interface element so that at least one boundary of the interface element is aligned with a boundary of the detection area.

3. The method of claim 1, wherein: The step of determining the position of the graphical interface element includes determining the display position of the graphical interface element so that at least two continuous edges of the graphical interface element are aligned with at least two boundaries of the detection area respectively.

4. The method according to any one of the preceding claims, wherein the method further comprises the following steps: - determining at least one size of the graphical interface element so that the interface element covers an integer number of detection areas according to the size, -Adjusting the size of the graphical interface element according to the determined size.

5. A device for controlling a touch screen, the touch screen comprising: a display (504) adapted to display at least one graphical interface element at a first graphics resolution; and a touch surface (505) comprising a plurality of detection areas forming a detection grid, the detection grid having a resolution lower than the first resolution, the device further comprising a processor (501) coupled to a memory (502), the memory storing computer program instructions (503) configured to perform the following steps: - determining a display position of a graphical interface element on the display so that the amount of the detection area covered by the graphical interface element is minimized, - displaying the graphical interface element at the determined position, - When a contact is detected in a detection area covered by the graphical interface element, a function associated with the graphical interface element is triggered.

6. A touch screen comprising the control device according to claim 5.

7. An information medium comprising computer program instructions, the computer program instructions being configured to perform the steps of the method for controlling a touch screen as claimed in any one of claims 1 to 4 when the instructions are executed by a processor.

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