Abstract:
An apparatus with a first and second touch screen, where the first touch screen has a plurality of first touch sensors formed as a first grid of rows and columns and the second touch screen has a plurality of second touch sensors formed as a second grid of rows and columns. A first processor detects touch areas by scanning through the first touch sensors in a predetermined order along the rows and columns. A second processor detects touch areas by scanning through the second touch sensors in a predetermined order along the rows and columns. A controller causes that the first and second processors scan the first and second grids synchronized such that when the first and second touch screens are arranged side by side, neighboring first and second touch sensors are scanned substantially simultaneously.

Description:
TECHNICAL FIELD 
     The present invention generally relates to touch detection. The invention relates particularly, though not exclusively, to detecting touch on a surface that comprises more than one touch detection screen. 
     BACKGROUND ART 
     Touch screens have become common in modern mobile phone user interfaces. A touch screen typically comprises a surface with a matrix of touch sensitive nodes and a processor connected to scan through the matrix to detect the state of each node. There are various types of touch screens, such as resistive, capacitive, optical and pressure sensitive touch screens. The physical operation of the nodes depends on the type of the touch screen, but in common the nodes electrically indicate touch of a finger or stylus to the processor at the node in question and the processor deduces from the states of the nodes the area or areas being touched in a particular detection frame. The detected areas of a detection frame are provided by the processor to a host device for processing as user input. 
     SUMMARY 
     According to a first example aspect of the invention there is provided an apparatus comprising:
         a first touch screen comprising a plurality of first touch sensors formed as a first grid of rows and columns;   a second touch screen comprising a plurality of second touch sensors formed as a second grid of rows and columns;   a first processor configured to detect touch areas by scanning through the first touch sensors in a predetermined order along the rows and columns;   a second processor configured to detect touch areas by scanning through the second touch sensors in a predetermined order along the rows and columns; and   a controller configured to cause the first and second processors to scan the first and second grids synchronized such that when the first and second touch screens are arranged side by side, neighboring first and second touch sensors are scanned substantially simultaneously.       

     The first processor may comprise the controller. 
     According to a second example aspect of the invention there is provided a method in an apparatus comprising a first touch screen comprising a plurality of first touch sensors formed as a first grid of rows and columns; and a second touch screen comprising a plurality of second touch sensors formed as a second grid of rows and columns; the method comprising:
         detecting touch areas by scanning through the first touch sensors in a predetermined order along the rows and columns;   detecting touch areas by scanning through the second touch sensors in a predetermined order along the rows and columns; and   causing that the first and second processors scan the first and second grids synchronized such that when the first and second touch screens are arranged side by side, neighboring first and second touch sensors are scanned substantially simultaneously.       

     According to a third example aspect of the invention there is provided a computer program comprising computer executable program code configured, when executed by the computer, to control an apparatus comprising a first touch screen comprising a plurality of first touch sensors formed as a first grid of rows and columns; and a second touch screen comprising a plurality of second touch sensors formed as a second grid of rows and columns; the controlling comprising causing the apparatus to:
         detect touch areas by scanning through the first touch sensors in a predetermined order along the rows and columns;   detect touch areas by scanning through the second touch sensors in a predetermined order along the rows and columns; and   cause the first and second processors to scan the first and second grids synchronized such that when the first and second touch screens are arranged side by side, neighboring first and second touch sensors are scanned substantially simultaneously.       

     According to a fourth example aspect of the invention there is provided a memory medium carrying the computer program of the third aspect. 
     The memory medium may comprise a digital data storage such as a data disc or diskette, optical storage, magnetic storage, holographic storage, opto-magnetic storage, phase-change memory, resistive random access memory, magnetic random access memory, solid-electrolyte memory, ferroelectric random access memory, organic memory or polymer memory. The memory medium may be formed into a device without other substantial functions than storing memory or it may be formed as part of a device with other functions, including but not limited to a memory of a computer, a chip set, and a sub assembly of an electronic device. 
     Different non-binding example aspects and embodiments of the present invention have been illustrated in the foregoing. The above embodiments are used merely to explain selected aspects or steps that may be utilized in implementations of the present invention. Some embodiments may be presented only with reference to certain example aspects of the invention. It should be appreciated that corresponding embodiments may apply to other example aspects as well. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1   a  shows a schematic drawing of an apparatus according to a first example aspect of the invention; 
         FIG. 1   b  shows a schematic drawing of the apparatus of  FIG. 1   a  with further details; 
         FIG. 2  shows a schematic drawing of an apparatus according to a second example aspect of the invention; 
         FIG. 3  shows a schematic drawing of a switch grid for illustrating a first example implementation of a touch screen for an apparatus of  FIGS. 1   a  and  1   b;    
         FIG. 4  shows a timing chart illustrative of gate timing for  FIG. 3 ; 
         FIG. 5  shows a schematic flow chart of a process according to a fourth example aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, like numbers denote like elements. 
       FIG. 1   a  shows a schematic drawing of an apparatus  100  according to a first example aspect of the invention. The apparatus  100  may be, for instance, a handheld device with a touch screen, such as a mobile phone, internet browser, electronic book, navigator, personal digital assistant, game device, or multifunction device with more than one of these functionalities. 
     The apparatus  100  comprises two major parts for explaining the operation of the apparatus  100 : a baseband part  110  and a display module  120 . 
       FIG. 1   b  shows a schematic drawing of the apparatus of  FIG. 1   a  with further details.  FIG. 1   b  shows that the baseband part comprises an engine  112  that is explained with further detail in conjunction with  FIG. 2 , and a backlight controller  114 . The display module  120  comprises a display driver  121  and a display panel  122  under control of the display driver. The display panel is, for example, a liquid crystal, plasma, or organic light emitting diode (OLED) based display panel. The display module  120  further comprises a touch screen  123  and a touch screen controller  124  for controlling the touch screen  123  and for obtaining touch information from the touch screen  123 . The touch screen  123  is, for example, a resistive, capacitive, optical or pressure sensitive touch screen, or any combination of these. 
     The touch screen controller  124  further comprises an interworking port  125 . Moreover, the display module comprises a backlight  126  for the display panel  122 . 
     The engine  112  is connected with the display driver  121  and touch screen controller  124  such that the engine can feed desired content for display and receive touch information from the touch screen  123 . Moreover, the engine is connected to the backlight controller so as to steer the backlight  126  with the backlight controller  114 . 
     The implementation of the various functional blocks shown in  FIG. 1   b  is known except that the touch screen controller  124  is provided with an interworking port  125  that is configured to output or input interworking information. This interworking is disclosed further in connection with  FIG. 5 . It helps understanding that description to describe some further structures and operation according to some embodiments of the invention. 
       FIG. 2  shows a schematic drawing of an apparatus  200  according to a second example aspect of the invention. The apparatus  200  comprises the engine  112  of  FIG. 1   b , here drawn as an assembly of a processor  210 , memory  220  comprising a work memory  222  and persistent memory  224  with software  226 . Thus, the engine  112  in this example embodiment is software or firmware based engine. The processor  210  is, for instance, a microprocessor with one or more cores, a digital signal processor, an application specific integrated circuit (ASIC), a field programmable gate array, a microcontroller or a combination of such elements. The processor  210  is configured to execute computer executable program code of the software  226  in the work memory  222  and according to the program code, the processor is configured to control different functionally connected devices. In  FIG. 2 , the processor  210  is functionally connected to a communication unit  230  that in this example embodiment is a radio communication unit, and to a pair of adjacent or adjacently configurable display modules. The display modules are denoted as a first display module  120 ′ and a second display module  120 ″. The first display module  120 ′ is configured to operate as a master and configured to control the second display module  120 ″ with interworking information provided via interworking ports  125  of the first and second display modules  120 ′ and  120 ″. 
     In  FIG. 2 , the two different display modules are denoted with reference signs  120 ′ and  120 ″ indicative of that their structure may be otherwise identical with the display module  120  of  FIG. 1   b , except that in one of the display modules, the touch screen controller  124 ′ is configured as a master and in another display module, the touch screen controller  124 ″ is configured as a slave. In some embodiments, though, the display modules differ by structure. For instance, the touch screens in the different display modules may be of different types. The two touch screen controllers are communicatively connected such that the master touch screen controller  124 ′ feeds interworking information to the slave touch screen controller  124 ″ via the interworking ports  125 . 
       FIG. 3  shows a schematic drawing of a switch grid for illustrating a first example implementation of the touch screen  123  for an apparatus of  FIG. 1   b . Generally, a touch screen comprises touch sensors which in this example are exemplified by switches that react to touching the touch screen  123 . It is appreciated, though, that in some example embodiments of the invention, the touch screen  123  is configured to form a virtual grid or logical grid i.e. the touch screen need not be physically divided into rows and columns as will be described in the following. Due to the grid form, the touch screen  123  can also be referred to as a matrix touch screen. In  FIG. 3 , there is a grid of switches  314 . By pressing the touch screen at given point or area, the effected switches will close and connect respective signal lines that are in row lines  311  and read-out lines  313  (as columns in  FIG. 3 ). While in  FIG. 3  the row lines and read-out lines are orderly laid in a matrix form, it is appreciated that there are other example embodiments in which the rows and columns are not in 90 degree angle and/or the rows and/or columns conform to non-linear form (e.g. zigzag or conform to a meandering line). Generally, it suffices that subsequent processing is aware of the location of each touch sensor with regard to associated display if the touch screen is to be used as a pointing device for the display. The read-out lines are each fed with a voltage V from voltage supply line  312 . The row lines  311  are grounded one by one with respective gate circuits  315  e.g. transistors TG n  to TG n+2  under control of a timing controller  316 . The timing controller  316  is configured to cause each of the gate circuits  315  in turn to ground  317  each of the row lines  311 . A read-out circuit  318  has respective inputs for each read-out line  313 . When a given part of the touch screen is touched, the respective switches  314  draw current to ground from the read-out line in question. Based on the alternating grounding of the row lines  311 , the read-out circuit determines the row on which a particular switch is being actuated to connect the read-out line to ground. Such grounding by a switch may further involve applying resistance such that the grounding does not cause excess current. However, even in that case, the voltage at a particular read-out line of the read-out circuit input decreases in a manner that enables the read-out circuit to detect contact at that particular read-out line. The crossing between the detected grounded read-out line and the grounded row-line thus matches with the switch that is being actuated. 
     In effect, the voltage at a read-out line is thus high when each switch on that read-out line is open. Correspondingly, the voltage is low when a switch at a grounded row line is closed. 
     Every row line  311  is grounded once during one touch scanning period. The touch scanning period is, for instance, 1 s per 20 to 100, e.g. 1/60 s. 
     The touch screen of  FIG. 1   b  resides aligned with (e.g. underneath or on top of) a display such that a user may touch on a given part of displayed image and the corresponding part of image can be determined. Each switch of the touch screen may correspond to one or more pixels (e.g. to areas of two times two pixels or four times four pixels of the display). However, it is appreciated that in another aspect, touch screens are used without a display aligned with the touch screen. 
     The timing controller  316  is, in turn, controlled by the touch screen controller  124 . In an alternative embodiment, the timing controller  316  is a part of the touch screen controller  124 . 
     In the example shown in  FIG. 2 , one touch screen controller was used to control another touch screen controller by means of interworking information that indicates timing for a slave touch screen controller. In an alternative embodiment, the timing controller  316  of the master touch screen is connected to the row lines of two touch screens  123  such that the neighboring row lines are connected to a first gate circuit  315  and each subsequent row line of each touch screen  123  is connected to a subsequent gate circuit  315 . In this embodiment, suitable connectors are provided between the two touch screens  123  either as analog circuitry in which there is a separate connection line for each gate circuit  315  or as digital circuitry in which one or more signal line is multiplexed to indicate plurality of different row lines. 
       FIG. 4  shows a timing chart illustrative of gate timing for  FIG. 3 . The timing chart visualizes how successive row lines are scanned (for each read-out line) at sub-sequent periods of time such that contacts at a further read-out line are detected at a later moment of time. 
     It is now explained how the touch screen is scanned line by line to detect touch. Let us next resume to consider operation in the apparatus of  FIG. 2  with reference to  FIG. 5  that shows a schematic flow chart of a process according to a fourth example aspect of the invention. 
     Two touch screens  123  reside side by side so that they each have grids (as illustrated in  FIG. 4 ) and at neighboring sides of the grids, there are neighboring row lines  311  of each touch screen  123  adjacent to each other. The engine  112  then instructs  510  the touch screens  123  to scan for touched area or areas on the touch screens  123 . The master touch screen controller  124 ′ provides  520  the slave touch screen controller  124 ″ with interworking information via the interworking ports  125  such that the slave touch screen  123 ″ and the master touch screen  123 ′ scan the neighboring row lines  311  in a synchronized manner. That is, the neighboring lines are scanned substantially simultaneously and with substantially common intervals. Moreover, in an example embodiment of the invention, the master touch screen  123 ′ and the slave touch screen  123 ″ scan the row lines in an order in which the scanning proceeds outwards of the neighboring row lines. The master touch screen controller  124 ′ may also control  530  the scanning direction of the slave touch screen  123 ″. This controlling by the master touch screen controller  124 ′ may take place by instructing the scanning direction in the interworking information. Each of the two touch screens  123  is repeatedly scanned  540 , row by row, and touch areas are recognized  550  by the engine  112 . 
     By scanning substantially simultaneously the neighboring row lines  311 , it is quicker and more robust to detect a simultaneous touch that spans onto two different matrix touch screens than if the two touch screens were scanned at the neighboring lines at different, random moments of time. The substantially simultaneous scanning may also avoid or mitigate detecting as two separate contacts a touch that bridges edges of two adjacent touch screens. 
     It is appreciated that in some embodiments of the invention, the two touch screens  123  have different number of rows in the grid. In such a case, there are various ways to maintain substantially simultaneous scanning of the neighboring row lines  311 . First, the number of row lines in one touch screen may be a multiple of the number of row lines in the other touch screen. Then, the touch screen with fewer row lines can be scanned a number of times per one scanning of the other touch screen. Second, both touch screens can be scanned so that all the row lines are scanned within common scanning period. The interval between subsequent row lines then varies between the two touch screens. Third, the touch screens can be scanned at their own rates such that the touch screen that is first entirely scanned waits until the other touch screen scanning resumes at the neighboring row line. 
     The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments of the invention a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented above, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention. 
     For example, in connection with  FIG. 2 , it was disclosed how one touch screen controller  124  may function as a master that controls the operation of another touch screen controller. In another example embodiment of the invention, a controlling component controls two different touch screens such that their operation takes place in a synchronized manner so that each touch screen scans the neighboring row lines substantially simultaneously. The controlling component is, for instance, a common component also used for some other purpose or a dedicated component. The engine  112  can be used as an example of suitable common component. In either case of using a common or dedicated component, the controlling component may provide controlled touch screens with timing information and optionally also with direction information that determines the order (direction) in which controlled. The controlling component may provide both touch screens with timing. Alternatively, the controlling component may comprise an input configured to receive a timing related signal from a first touch screen and a processor configured to control the timing of a neighboring second touch screen according to the timing of the first touch screen. 
     Furthermore, some of the features of the above-disclosed embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present invention, and not in limitation thereof. Hence, the scope of the invention is only restricted by the appended patent claims.