Abstract:
An multi-touch detection system ( 100 ) separately determines each of the coordinates of multiple touches and is able to correctly pair the coordinates, the touch panel includes multiple (e.g., two or four) separate sections ( 104, 106, 404, 406, 504, 506, 508, 510 ) to detect touches in different areas. The system ( 100 ) is able to operate at high refresh rates allowing speed sensitive applications to be supported.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to touch pads and touch screens. 
       BACKGROUND 
       [0002]    Touch screens have touch coordinate detection systems mounted at the front of displays (e.g., CRTs, LCDs). Many different types of touch detection systems based on different physical principles have been tried. Examples include touch screens based on optical, acoustical, and electronic technologies and there are numerous variations within each category. Some touch screen technologies use an analog/vector approach to locate touches and therefore do not localize touches on a predetermined grid. However, many types of touch screens localize touches using a fixed 2-D grid which can be based on optical or electrical impedance change sensing. 
         [0003]    The category of touch panels that use a predetermined grid can be further sub-divided into two categories. One category is referred to herein as “M×N” (where M and N stand for integers and M×N is the product of those integers). Touch screens in the M×N category effectively divide the sensing area into M×N independent sensors, so that when a touch is detected by an M×N system, both of the coordinates (e.g., the X and Y coordinates) of the touch are determined at once because each individual sensor has a particular X coordinate and a particular Y coordinate. A drawback of some electrical M×N systems is that there are many individual sensors to be interrogated. The number of sensors to be interrogated implies a requirement for a high bandwidth data bus or a slow frame rate for sensing. For certain applications of touch screens, such as hand writing recognition, it is desirable to achieve a high rate of touch coordinate updating, and for such applications M×N systems present limitations. 
         [0004]    Another category of touch panels that uses a predetermined grid is referred to herein as “M+N” (where M and N stand for integers and M+N is the sum of those integers). An M+N type touch panel separately detects the X coordinate of touches using one sub-system (e.g., including an array of vertically extending electrodes) and separately detects the Y coordinates using another sub-system (e.g., including an array of horizontally extending electrodes). Generally, for touch screens of practical interest, the integers M and N will have sufficiently high values such that M×N will greatly exceed M+N. Accordingly, an M+N system will require far lower data rates to achieve a certain touch coordinate update rate, and therefore applications that require high touch coordinate update rates such as hand writing recognition are more easily supported. 
         [0005]    The above-mentioned separation of the detection of the X and Y coordinates presents no problem if only a single touch is to be detected, because the X and Y coordinates of the single touch are assumed to be correlated. However, in order to support more complicated touch screen interactions (e.g., gestures) it is desirable to be able to detect two or more touches contemporaneously. For example a user can touch a touch screen using their thumb and index finger and move their thumb and index finger along arcuate paths in order to input a rotation command which could then be interpreted to call for rotation of a displayed graphic (e.g., map), for example. In the case of an M+N system that detects the X and Y coordinates separately, two contemporaneous touches (i.e., a multi-touch) can confound the system because the system will be unable to unambiguously associate the two detected X coordinates with the two detected Y coordinates. Consequently, software applications that rely on the M+N touch detection system will be unable to determine if the user called for a clockwise rotation or a counter clockwise rotation, for example. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0006]    The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention. 
           [0007]      FIG. 1  is a diagram of a multi-touch detection system according to an embodiment of the invention; 
           [0008]      FIG. 2  is a block diagram of an electronic apparatus using the multi-touch detection system shown in  FIG. 1 ; 
           [0009]      FIG. 3  is an illustration of a prior art M+N touch screen system highlighting the ambiguity in detecting the location of two contemporaneous touches; 
           [0010]      FIG. 4  is a schematic illustration of a touch screen system according to an embodiment of the invention; 
           [0011]      FIG. 5  is a schematic illustration of a touch screen system according to another embodiment of the invention; 
           [0012]      FIG. 6  is a schematic illustration showing how a resizing gesture is detected by a touch screen system according to an embodiment of the invention; and 
           [0013]      FIG. 7  is a flowchart of a method of detecting a two-touch touch screen gesture according to an embodiment of the invention. 
       
    
    
       [0014]    Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. 
       DETAILED DESCRIPTION 
       [0015]    Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to touch screens. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. 
         [0016]      FIG. 1  is a diagram of a multi-touch detection system  100  according to an embodiment of the invention. As used herein the term “multi-touch detection system” refers to a touch detection system capable of registering more than one contemporaneous touch events. The system  100  includes a multi-touch panel  102  that includes an upper rectangular section  104  and a lower rectangular section  106 . Alternatively, the multi-touch panel  102  and its sections could be non-rectangular in shape. The multi-touch panel  102  shown in  FIG. 1  is a tandem M+N type capacitive sensing type of multi-touch panel. Alternatively, a multi-touch panel based on a different physical principle could be used such as an optical or resistive sensing type of touch panel. As shown in  FIG. 1  the two sections  104 ,  106  are formed on a common transparent planar base  108 , however alternatively the two sections  104 ,  106  can be formed on separate planar bases that are joined together along edges. The planar base  108  and the electrodes  110 ,  112  are transparent allowing the touch panel  102  to be suitable for use in a touch screen system, however alternatively, if the system  100  is to be used in a touch pad application, the planar base  108  and the electrodes  110 ,  112  need not be transparent. In the case that the multi-touch panel is to be transparent the planar base  108  is suitably made of glass or transparent plastic, for example and the electrodes  110 ,  112  are suitably made of ITO, for example. Rather than using a planar base, alternatively a flexible or conformable base is used, e.g., in a wearable or foldable display application. 
         [0017]    A plurality of vertically extending sensing electrodes  110  (of which only three are numbered to avoid crowding the drawing) are positioned side-by-side (in a horizontal array) in the upper rectangular section  104 . Additionally a plurality of horizontally extending sensing electrodes  112  are positioned one above another (in a vertical array) in the upper rectangular section  104 . The vertically extending sensing electrodes  110  and the horizontally extending sensing electrodes  112  are suitably located on opposite faces of the planar base  108 , so that the planar base  108  provides electrical insulation between the two sets of electrodes  110 ,  112 . Alternatively, other provisions are made for insulating the two sets of electrodes  110 ,  112  from each other. As shown in  FIG. 1  both sets of electrodes  110 ,  112  include pad areas  114  that are connected by narrower width lines  116 . The pad areas  114  from the two sets of electrodes  110 ,  112  do not overlap, only the narrow width lines  116  have a small overlap where they cross. The latter arrangement limits the parasitic capacitive coupling between adjacent electrodes in one of the sets of electrodes  110  ( 112 ) by way of electrodes in the other of the sets of electrodes  112  ( 110 ). In this way the panel  102  is made more sensitive to capacitance changes induced by a user&#39;s touch. 
         [0018]    Both of the sets of electrodes  110 ,  112  are coupled through a first signal bus  118  to a first microcontroller  120 . According to one mode of operation, the first microcontroller  120  will interrogate each of the vertically extending sensing electrodes  110  and horizontally extending sensing electrodes  112  separately. The first microcontroller is one form of electrical circuit that may be used to interrogate the sensing electrodes  110 ,  112 ; however, alternatively other types of electrical circuits may be used for this purpose. The individual sensing electrodes  110 ,  112  can be interrogated by applying a signal to measure the capacitance. The capacitance of electrodes proximate a user&#39;s touch will change thereby revealing the location of the user&#39;s touch. The vertically extending sensing electrodes  110  can determine the X coordinate(s) of a user&#39;s touch or multiple contemporaneous touches and the horizontally extending electrodes  112  can determine the Y coordinate(s) of the user&#39;s touch or multiple contemporaneous touches. Note that for two contemporaneous touches (e.g., with a thumb and forefinger) there are two X coordinates and two Y coordinates and the system  100  can not necessarily properly pair the X and Y coordinates together-there are four possible pairings only two of which are valid. 
         [0019]    Note however that the system also includes the lower rectangular section  106  and that the sections  104 ,  106  are sized in view of the overall multi-touch panel  102  size and in view of the typical spacing between fingers for supported gestures (e.g., 5 cm for thumb to forefinger multi-touch spacing), such that it can be expected that one touch of a multi-touch (e.g., a forefinger touch) will be in the upper rectangular section  104  of the multi-touch panel  102  and another touch of a multi-touch (e.g., a thumb touch) will be in the lower rectangular section  106  of the multi-touch panel  102 . 
         [0020]    Similar to the upper rectangular section  104 , the lower rectangular section  106  includes a second set of vertically extending sensing electrodes  122  positioned side-by-side (in a horizontal array) and a second set of horizontally extending sensing electrodes  124  positioned one above another (in a vertically array). The second set of vertically extending electrodes  122  and the second set of horizontally extending electrodes  124  are coupled through a second signal bus  126  to a second microcontroller  128  that interrogates the lower rectangular section  106  of the multi-touch panel  102  in a like manner to the interrogation of the upper rectangular section  104  by the first microcontroller  120 . The first microcontroller  120  and the second microcontroller  128  are parts of a larger multi-touch panel controller  130 . Alternatively, the multi-touch panel controller  130  includes a single microcontroller that interrogates both the sections  104 ,  106  of the touch panel  102 . 
         [0021]      FIG. 2  is a block diagram of an electronic apparatus  200  using the multi-touch detection system  100  shown in  FIG. 1 . The apparatus  200  can comprise a smartphone, a Portable Digital Assistant (PDA), a tablet computer, an ultra portable computer, a Digital Video Disk (DVD) player, a remote controller, or an MP3 player, for example. In the electronic apparatus  200 , the multi-touch panel  102  is mounted over a display  202  forming a touch screen  204 . Alternatively, the multi-touch panel  102  can be functionally integrated with the display. A display controller  206  is drivingly coupled to the display  202  and the multi-touch panel controller  130  is coupled to the multi-touch panel  102 . A master controller (e.g., microprocessor)  208  is coupled to the display controller  206  and the multi-touch panel controller  130 . The master controller  208  runs an operating system  210  and software  212  that includes Graphical User Interface (GUI) software that supports multi-touch gestures, such as the rotation gesture described above and a non-proportional scaling gesture described below. 
         [0022]      FIG. 3  is an illustration of a prior art M+N touch screen system  300  highlighting the ambiguity in detecting the location of two contemporaneous touches. In this case when the user touches a touch panel  302  the system  300  will read out two X coordinates (e.g., Xa and Xb) and two Y coordinates (e.g., Ya and Yb) but will not be able to determine how to properly pair the X and Y coordinates to determine the true locations of the two touches of the multi-touch. For example, is the forefinger&#39;s touch (X 1 , Y 1 ) of the multi-touch represented by (Xa, Yb) or (Xb, Yb)? Also, is the thumb&#39;s touch (X 2 , Y 2 ) of the multi-touch represented by (Xa, Ya) or (Xb, Ya)? Thus, for example, there is an ambiguity as to whether the two touches of the multi-touch are at the upper right and lower left as marked by the solid line circles or at the upper left and lower right as marked by the dashed circles. 
         [0023]    In  FIGS. 3-6  the subscripts T 1  indicates a first touch panel scan period and T 2  a subsequent touch panel scan period. M+N touch panels will typically periodically scan the touch panel at a predetermined frame rate. 
         [0024]      FIG. 4  is a schematic illustration of a touch screen system  400  according to an embodiment of the invention. The touch screen system  400  includes a multi-touch panel  402  that includes an upper rectangular section  404  and a lower rectangular section  406 . Because the multi-touch panel  402  includes the two sections  404 ,  406 , there is no ambiguity in associating the X and Y coordinates of two touches of a single multi-touch if the two touches are not in the same section  404 ,  406  of the multi-touch panel  402 . Thus, the system  400  can correctly determine the X and Y coordinates of a first touch labeled (X 1 , Y 1 ) and a second touch (X 2 , Y 2 ) of a multi-touch gesture during two successive time periods, labeled T 1  and T 2 . For example, the first touch (X 1 , Y 1 ) could be using a forefinger and the second touch (X 2 , Y 2 ) could be using a thumb. 
         [0025]    An electronic apparatus e.g.,  200 , that incorporates the touch screen system  400  is suitably programmed based on ergonomic assumptions on the range of motion of fingers engaged in two contemporaneous touches and under these assumptions the sense of rotation, i.e., clockwise (CW) or counterclockwise (CCW), can be construed based on the detected touch coordinates during two or more successive frame scan periods. 
         [0026]      FIG. 5  is a schematic illustration of a touch screen system  500  according to another embodiment of the invention. The system  500  includes a touch panel  502  that is divided into four rectangular quadrants including an upper left quadrant  504 , an upper right quadrant  506 , a lower right quadrant  508 , and a lower left quadrant  510 . The four quadrants  504 ,  506 ,  508 ,  510  are served by a first microcontroller  512 , a second microcontroller  514 , a third microcontroller  516 , and a fourth microcontroller  518 , respectively. Each quadrant  504 ,  506 ,  508 ,  510  in conjunction with its associated microcontroller  512 ,  514 ,  516 ,  518  serves as a sensing sub-system. Alternatively a single microcontroller is used to interrogate all four quadrants. Providing the four quadrants  504 ,  506 ,  508 ,  510  allows touch panel  502  to be able to detect double touches even if both touches are in the lower half or both touches are in the upper half of the touch panel  502 . Thus, more variability in the way users execute touch screen gestures can be supported and a greater variety of touch screen gestures can be supported. Note that alternatively the touch panels according to embodiments of the invention can be further subdivided however there will be diminishing returns in terms of supported gestures at the expense of increased complexity and/or bandwidth requirements for the electronics (e.g., microcontrollers) used to read the touch panel. 
         [0027]    Initial multi-touches of two fingers are labeled (X 1 , Y 1 ) T1  and (X 2 , Y 2 ) T1  and final positions of the two touches of a subsequent multi-touch (for the illustrated gesture) are labeled (X 1 , Y 1 ) T2  and (X 2 , Y 2 ) T2 . Such a gesture can be used to enter a rotation command (clockwise, in this example). The rotation command can be used for various purposes, such as for example rotating a graphic displayed by the touch screen system  500 . 
         [0028]      FIG. 6  is a schematic illustration showing how a resizing gesture for a circle  602  is detected by a touch screen  600  system according to an embodiment of the invention. Initially a circle  602  is displayed on the touch screen  600 . In order to perform a non-proportional scaling of the circle  602  in a user-specified direction, the user touches two fingers on opposite sides of the circle  602 , which the system  600  interprets as an initial multi-touch with coordinates (X 1 , Y 1 ) T1  and (X 2 , Y 2 ) T1 . The direction of scaling is indicated by a combination of the virtual line connecting the positions of the two touches of the initial multi-touch and the virtual line connected the positions of the two touches of a subsequent multi-touch. One example of such a gesture occurs when the virtual line associated with the initial touch and the virtual line associated with the final touch are collinear. In this case, the user spreads the two fingers apart in order to enter a scaling command. A subsequent multi-touch is detected by the system and determined to be at coordinates (X 1 , Y 1 ) T2  and (X 2 , Y 2 ) T2 . Based on the differences between the coordinates of the initial multi-touch (e.g., (X 1 , Y 1 ) T1  and (X 2 , Y 2 ) T1 ) and the coordinates of the subsequent multi-touch (e.g., (X 1 , Y 1 ) T2  and (X 2 , Y 2 ) T2 ), the circle is then stretched into an ellipse  604  with its major axis inclined in a direction indicated by the user&#39;s two detected multi-touches. Alternatively, the user may draw the two fingers together whereby the said circle would be reformed into an ellipse having its minor axis inclined in a direction indicated by the user&#39;s two detected multi-touches. This is but one example of a two multi-touch gesture that can be supported. Other gestures comprised of combinations of rotation gestures and non-proportional scaling gestures, e.g., gestures in which the aforementioned virtual lines associated with an initial multi-touch and subsequent multi-touch are not collinear, can also be supported. 
         [0029]      FIG. 7  is a flowchart of a method  700  of detecting a two-touch touch screen gesture according to an embodiment of the invention. The method  700  can be implemented in software that is stored in a memory and executed by a processor that is coupled to a touch panel structured according to embodiments described above. In block  702 , during a first time period, a first sensing sub-system (e.g., upper rectangular section  104  and first microcontroller  120 ) is used to detect coordinates (e.g., X and Y coordinates) of a first touch of an initial multi-touch in a first part of a touch panel. In block  704 , also during the first time period, a second sensing sub-system (e.g., the lower rectangular section  106  and the second microcontroller  128 ) is used to detect coordinates of a second touch of the initial multi-touch in a second part of the touch panel. In block  706  during a second time period following the first time period, the first sensing sub-system is used to detect new coordinates of a first touch of a subsequent multi-touch in the first part of the touch panel. 
         [0030]    Note that some embodiments contemplated may be programmed to assume that touches by the same finger are always in the same half (e.g., upper or lower) of the touch panel, however this does not apply to all embodiments. This assumption is based in part on ergonomic considerations for the range of motion of the human hand while engaged in contemporaneous thumb and index finger touches and also on the assumption that the user will be instructed through a user manual to perform touch screen gestures in a certain manner. 
         [0031]    In block  708 , also during the second time period, the second sensing sub-system is used to detect new coordinates of a second touch of the subsequent multi-touch in the second part of the touch panel. In block  710  the detected touch coordinates are sent to a master controller (e.g.,  206 ) and in block  712  the coordinates are processed to infer a gesture such as a CW or CCW rotation or a scaling command, for example. 
         [0032]    Alternatively rather than providing a touch panel based on Cartesian coordinates, a touch panel based on polar coordinates or another coordinate system can be used. 
         [0033]    In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. 
         [0034]    It will be appreciated that embodiments of the invention described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of touch panels described herein. The non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method to perform touch panel functions. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. Thus, methods and means for these functions have been described herein. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation. 
         [0035]    In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.