PATENT DOCUMENT

Publication Number: US-8576193-B2
Application Number: US-11007508-A
Country: US
Kind Code: B2

Title: Brick layout and stackup for a touch screen

Abstract:
A touch sensor panel is disclosed having an array of co-planar single-layer touch sensors fabricated on a single side of a substrate. The sense (or drive) lines can be fabricated in a single strip as columnar or zig-zag patterns in a first orientation, and the drive (or sense) lines can be fabricated as rows of polygonal (e.g. brick-shaped or pentagonal) conductive areas in a second orientation. Each sense (or drive) line in the first orientation can be coupled to a separate metal trace in the border area of the touch sensor panel, and each polygonal area in the second orientation can also be coupled to a metal trace in the border area of the touch sensor panel. The metal traces can allow both the row and column lines to be routed to the same edge of the substrate for flex circuit attachment.

Claims:
What is claimed is: 
     
       1. A capacitive touch sensor panel, comprising:
 a plurality of sense lines formed on a single layer and supported on one side of a substrate; 
 a plurality of drive lines formed on the same side of the substrate as the plurality of sense lines, each of the plurality of drive lines formed along rows from a corresponding plurality of polygonal areas electrically coupled together by a plurality of traces routed to a plurality of bus lines including at least a first and second bus line, the plurality of sense lines formed of a plurality of columns, the plurality of sense lines and the plurality of drive lines forming an array of capacitive sensors; 
 the plurality of connecting traces routed adjacent to at least a first and second column of the polygonal areas, each column having at least a first and second polygonal area disposed in the same position in each column relative to the plurality of bus lines, the distance between the first polygonal area and the bus lines being different from the distance between the second polygonal area and the bus lines; 
 the plurality of connecting traces formed on the same side of the substrate as the plurality of sense lines; 
 a first connecting trace coupling the first bus line to the first polygonal area of the first column and a second connecting trace coupling the first bus line to the second polygonal area of the second column; and 
 a third connecting trace coupling the second bus line to the second polygonal area of the first column, and fourth connecting trace coupling the second bus line to the first polygonal area of the second column. 
 
     
     
       2. The touch sensor panel as recited in  claim 1  wherein the traces are connected to the polygonal areas and the bus lines so as to interleave the polygonal areas. 
     
     
       3. The touch sensor panel of  claim 1 , the touch sensor panel integrated within a computing system. 
     
     
       4. The touch sensor panel of  claim 3 , computing system integrated within a mobile telephone. 
     
     
       5. The touch sensor panel of  claim 3 , the computing system integrated within a media player. 
     
     
       6. A method for improving a touch detection capability of a capacitive touch sensor panel having a plurality of drive lines and a plurality of sense lines formed on a same side of a single substrate, comprising:
 forming the plurality of drive lines from a plurality of polygonal areas electrically coupled together by a plurality of traces routed to a plurality of bus lines including at least a first and second bus line; 
 forming the plurality of sense lines as a plurality of columns; 
 routing the plurality of connecting traces adjacent to the polygonal areas on the same side of the substrate as the plurality of sense lines; 
 routing the plurality of connecting traces adjacent to at least a first and second column of the polygonal areas, each column having at least a first and second polygonal area disposed in the same position in each column relative to the plurality of bus lines, the distance between the first polygonal area and the bus lines being different from the distance between the second polygonal area and the bus lines; 
 a first connecting trace coupling the first bus line to the first polygonal area of the first column and a second connecting trace coupling the first bus line to the second polygonal area of the second column; and 
 a third connecting trace coupling the second bus line to the second polygonal area of the first column, and fourth connecting trace coupling the second bus line to the first polygonal area of the second column. 
 
     
     
       7. The method of  claim 6 , further comprising configuring the one or more ground guards for shunting near-field electric field lines. 
     
     
       8. A mobile telephone including a touch sensor panel, the touch sensor panel comprising:
 a plurality of sense lines formed on a single layer and supported on one side of a substrate; 
 a plurality of drive lines formed on the same side of the substrate as the plurality of sense lines, each of the plurality of drive lines formed along rows from a corresponding plurality of polygonal areas electrically coupled together by a plurality of traces routed to a plurality of bus lines, including at least a first and second bus line, the plurality of sense lines formed of a plurality of columns, the plurality of sense lines and the plurality of drive lines forming an array of capacitive sensors; 
 the plurality of connecting traces routed adjacent to at least a first and second column of the polygonal areas, each column having at least a first and second polygonal area disposed in the same position in each column relative to the plurality of bus lines, the distance between the first polygonal area and the bus lines being different from the distance between the second polygonal area and the bus lines; 
 the plurality of connecting traces formed on the same side of the substrate as the plurality of sense lines; 
 a first connecting trace coupling the first bus line to the first polygonal area of the first column and a second connecting trace coupling the first bus line to the second polygonal area of the second column; and 
 a third connecting trace coupling the second bus line to the second polygonal area of the first column, and fourth connecting trace coupling the second bus line to the first polygonal area of the second column. 
 
     
     
       9. A media player including a touch sensor panel, the touch sensor panel comprising:
 a plurality of sense lines formed on a single layer and supported on one side of a substrate; 
 a plurality of drive lines formed on the same side of the substrate as the plurality of sense lines, each of the plurality of drive lines formed along rows from a corresponding plurality of polygonal areas electrically coupled together by a plurality of traces routed to a plurality of bus lines, including at least a first and second bus line, the plurality of sense lines formed of a plurality of columns, the plurality of sense lines and the plurality of drive lines forming an array of capacitive sensors; 
 the plurality of connecting traces routed adjacent to at least a first and second column of the polygonal areas, each column having at least a first and second polygonal area disposed in the same position in each column relative to the plurality of bus lines, the distance between the first polygonal area and the bus lines being different from the distance between the second polygonal area and the bus lines; 
 the plurality of connecting traces formed on the same side of the substrate as the plurality of sense lines; 
 a first connecting trace coupling the first bus line to the first polygonal area of the first column and a second connecting trace coupling the first bus line to the second polygonal area of the second column; and 
 a third connecting trace coupling the second bus line to the second polygonal area of the first column, and fourth connecting trace coupling the second bus line to the first polygonal area of the second column.

Description:
FIELD OF THE INVENTION 
     This relates generally to input devices for computing systems, and more particularly, to a touch sensor panel capable of being fabricated on a single side of a substrate. 
     BACKGROUND OF THE INVENTION 
     Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch sensor panels, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface. The touch sensor panel can be positioned in front of a display screen so that the touch-sensitive surface covers the viewable area of the display screen. Touch screens can allow a user to make selections and move a cursor by simply touching the display screen via a finger or stylus. In general, the touch screen can recognize the touch and position of the touch on the display screen, and the computing system can interpret the touch and thereafter perform an action based on the touch event. 
     Touch sensor panels can be implemented as an array of pixels formed by multiple drive lines (e.g. rows) crossing over multiple sense lines (e.g. columns), where the drive and sense lines are separated by a dielectric material. In some touch sensor panels, the row and column lines can be formed on different substrates. Such touch sensor panels can be expensive to manufacture, because processing must be performed on two different substrates. In addition, the use of two substrates can result in a thicker device. In other touch sensor panels, the drive and sense lines can be formed on the top and bottom sides of the same substrate. However, touch sensor panels having row and column lines formed on the bottom and top sides of a single substrate can also be expensive to manufacture, because thin-film processing steps must be performed on both sides of the glass substrate, which requires protective measures for the processed side while the other side is being processed. 
     SUMMARY OF THE INVENTION 
     This relates to a touch sensor panel having an array of co-planar single-layer touch sensors fabricated on a single side of a substrate for detecting single or multi-touch events (the touching of one or multiple fingers or other objects upon a touch-sensitive surface at distinct locations at about the same time). The sense (or drive) lines can be fabricated in a single strip as columnar or zig-zag patterns in a first orientation, and the drive (or sense) lines can be fabricated as rows of polygonal (e.g. brick-shaped or pentagonal) conductive areas in a second orientation. Because the drive and sense lines can be formed on the same layer, manufacturing costs can be reduced and the touch sensor panel can be made thinner. Each sense (or drive) line in the first orientation can be coupled to a separate metal trace in the border area of the touch sensor panel, and each polygonal area in the second orientation can also be coupled to a metal trace in the border area of the touch sensor panel. The metal traces in the border areas can be formed on the same side of the substrate as the drive and sense lines. The metal traces can allow both the row and column lines to be routed to the same edge of the substrate so that a small flex circuit can be bonded to a small area on only one side of the substrate. 
     In some embodiments, the connecting traces are routed along only one side of the bricks (a so-called “single escape” configuration). To couple the bricks in a particular row together, connecting traces, which are also formed from a conductive material, can be routed from the bricks along one side of the bricks in a single escape configuration to a particular bus line. Connections for each bus line and for the columns can be brought off the touch sensor panel through a flex circuit. 
     Because some bus lines can have much shorter connecting traces to the bricks as compared to other bus lines, the impedance and capacitance of certain bus lines can be much greater than that of other bus lines. Because of this imbalance, touch measurements for a given amount of touch may not be equalized across the touch sensor panel. Therefore, in some embodiments of the invention, the bricks coupled to a particular bus line can be interleaved so that each bus line sees a more uniform average impedance and capacitance, which can help equalize touch measurements across the touch sensor panel. 
     Interleaving can additionally provide increased power uniformity. Without interleaving, some drivers can have a small capacitive load, while others can have a large capacitive load. To ensure that the largest load can be properly driven, all drivers may be designed to drive the largest capacitive load, resulting in higher current requirements for all drivers, even those not driven with a large load. However, with interleaving, each driver can have a more moderate and roughly equivalent capacitive load, and the drivers need only be designed to drive the moderate capacitive load. 
     In some embodiments, the connecting traces are alternatingly routed along both sides of the bricks (a so-called “double escape” configuration). To couple the bricks in a particular row together, connecting traces, which are also formed from a conductive material, can be routed from the bricks along alternating sides of the bricks in a double escape configuration to a particular lower bus line or an upper bus line (although it should be understood that in other embodiments, only a single group of bus lines at either the top or bottom may be employed). The lower bus lines and upper bus lines, as well as connecting traces for columns, can be routed along the border areas and brought off the touch sensor panel through a flex circuit. 
     For the very longest routing traces, there can be on the order of about 6 pF of Csig transferred from the connecting traces to nearby sense lines, which can reduce the dynamic range budget and can make calibration difficult. Accordingly, a zig-zag double interpolated touch sensor panel can further reduce the stray capacitance between the connecting traces and the sense lines. Polygonal areas representing the drive (or sense) lines generally pentagonal in shape and staggered in orientation can be formed, with some of the polygonal areas near the end of the panel being cut-off pentagons. The sense (or drive) lines are zig-zag shaped. All connecting traces are routed in channels between pentagons. Because the connecting traces do not run alongside any sense (or drive) lines, but instead run between pentagons, the stray capacitance between the connecting traces and the sense (or drive) lines is minimized, and spatial cross-coupling is also minimized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a  illustrates an exemplary touch sensor panel including columns, rows of bricks, and connecting traces routed along only one side of the bricks according to embodiments of the invention. 
         FIG. 1   b  illustrates a close-up view of a portion of the exemplary touch sensor panel of  FIG. 1   a , showing bricks routed to bus lines using connecting traces in a single escape configuration according to embodiments of the invention. 
         FIG. 1   c  illustrates a portion of the exemplary touch sensor panel of  FIG. 1   a , including bricks associated with columns C 0  and C 1  and connecting traces coupling the bricks to the bus lines according to embodiments of the invention. 
         FIG. 2   a  illustrates a side view of a portion of an exemplary touch sensor panel showing the connections between connecting traces and bus lines according to embodiments of the invention. 
         FIG. 2   b  illustrates a top view of a portion of the exemplary bus lines of  FIG. 2   a  according to embodiments of the invention. 
         FIG. 3  illustrates a portion of an exemplary touch sensor panel including rows of bricks whose connecting traces are interleaved according to embodiments of the invention. 
         FIG. 4   a  illustrates an exemplary touch sensor panel including columns, rows of bricks, and connecting traces routed along both sides of the bricks according to embodiments of the invention. 
         FIG. 4   b  illustrates a close-up view of a portion of the exemplary touch sensor panel of  FIG. 4   a , showing bricks routed to lower bus lines using connecting traces in a double escape configuration according to embodiments of the invention. 
         FIGS. 5   a  and  5   b  illustrate top and side views of the effect of an exemplary ground guard on electric field lines emanating from a polygonal area of conductive material according to embodiments of the invention. 
         FIGS. 5   c  and  5   d  illustrate top and side views of the effect of an exemplary ground guard on electric field lines emanating from a connecting trace according to embodiments of the invention. 
         FIGS. 5   e  and  5   f  illustrate top and side views of the effect of an exemplary ground guard on electric field lines emanating from a polygonal conductive area and separated from a sense line by connecting traces according to embodiments of the invention. 
         FIG. 6  illustrates a portion of an exemplary zig-zag double interpolated touch sensor panel that can further reduce the stray capacitance between the connecting traces and the columns according to embodiments of the invention. 
         FIG. 7  illustrates an exemplary computing system operable with the touch sensor panel according to embodiments of this invention. 
         FIG. 8   a  illustrates an exemplary mobile telephone that can include the touch sensor panel according to embodiments of the invention. 
         FIG. 8   b  illustrates an exemplary media player that can include the touch sensor panel according to embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description of preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific embodiments in which the invention can be practiced. It is to be understood that other embodiments can be used and structural changes can be made without departing from the scope of the embodiments of this invention. 
     This relates to a touch sensor panel having an array of co-planar single-layer touch sensors fabricated on a single side of a substrate for detecting single or multi-touch events (the touching of one or multiple fingers or other objects upon a touch-sensitive surface at distinct locations at about the same time). In mutual capacitance embodiments, each sensor or pixel can be the result of interactions between drive and sense lines. The sense (or drive) lines can be fabricated in a single strip as columnar or zig-zag patterns in a first orientation, and the drive (or sense) lines can be fabricated as rows of polygonal (e.g. brick-shaped or pentagonal) conductive areas in a second orientation. Because the drive and sense lines can be formed on the same layer, manufacturing costs can be reduced and the touch sensor panel can be made thinner. Each sense (or drive) line in the first orientation can be coupled to a separate metal trace in the border area of the touch sensor panel, and each polygonal area in the second orientation can also be coupled to a metal trace in the border area of the touch sensor panel. The metal traces in the border areas can be formed on the same side of the substrate as the drive and sense lines. The metal traces can allow both the row and column lines to be routed to the same edge of the substrate so that a small flex circuit can be bonded to a small area on only one side of the substrate. 
     Although some embodiments of this invention may be described and illustrated herein primarily in terms of mutual capacitance multi-touch sensor panels, it should be understood that embodiments of this invention are not so limited, but can be additionally applicable to self-capacitance sensor panels and single-touch sensor panels. Furthermore, although the touch sensors in the sensor panel may be described and illustrated herein in terms of generally orthogonal arrangements of drive (or sense) lines formed as rows of rectangular bricks or pentagonal shapes, and sense (or drive) lines formed as columnar or zig-zag patterns, embodiments of this invention are not so limited, but can be additionally applicable to polygonal areas of other shapes and lines formed in other patterns. 
       FIG. 1   a  illustrates exemplary touch sensor panel  100  including sense (or drive) lines (C 0 -C 5 ) formed as columns  106  and rows of polygonal areas (bricks)  102 , where each row of bricks forms a separate drive (or sense) line (R 0 -R 7 ) according to embodiments of the invention. In the example of  FIG. 1   a , connecting traces  104  are routed along only one side of the bricks (a so-called “single escape” configuration). Although a touch sensor panel  100  having six columns and eight rows is shown, it should be understood that any number of columns and rows can be employed. Columns  106  and bricks  102  of  FIG. 1   a  can be formed in a co-planar single layer of conductive material. 
     To couple bricks  102  in a particular row together, connecting traces  104 , which are also formed from a conductive material, can be routed from the bricks along one side of the bricks in a single escape configuration to a particular bus line  110 . Ground isolation bars  108 , which are formed from conductive material, can be formed between connecting traces  104  and adjacent columns  106  to reduce the capacitive coupling between the connecting traces and the columns. Connections for each bus line  110  and for columns  106  can be brought off touch sensor panel  100  through flex circuit  112 . In touch screen embodiments, the sense lines, drive lines, connecting traces and ground isolation bars can be formed from a substantially transparent material such as Indium Tin Oxide (ITO), although other materials can also be used. The ITO layer can be formed on a single layer on either on the back of a coverglass or on a separate substrate. 
       FIG. 1   b  illustrates a close-up view of a portion of the exemplary touch sensor panel  100  of  FIG. 1   a , showing how bricks  102  can be routed to bus lines  110  using connecting traces  104  in a single escape configuration according to embodiments of the invention. In  FIG. 1   b , the longer connecting traces  104  (e.g. trace R 7 ) can be wider than the shorter connecting traces (e.g. trace R 2 ) to equalize the overall resistivity of the traces and to minimize the overall capacitive loads seen by the drive circuitry. 
       FIG. 1   c  illustrates a portion of exemplary touch sensor panel  100  of  FIG. 1   a  including bricks  102  associated with columns C 0  and C 1  and connecting traces  104  (illustrated symbolically as thin lines) coupling the bricks to bus lines  110  according to embodiments of the invention. In the example of  FIG. 1   b , which is drawn in a symbolic manner and not to scale for purposes of illustration only, bus line B 0  is coupled to brick R 0 C 0  (the closest brick to B 0  adjacent to column C 0 ) and R 0 C 1  (the closest brick to B 0  adjacent to column C 1 ). Bus line B 1  is coupled to brick R 1 C 0  (the next closest brick to B 0  adjacent to column C 0 ) and R 1 C 1  (the next closest brick to B 0  adjacent to column C 1 ). The pattern repeats for the other bus lines such that bus line B 7  is coupled to brick R 7 C 0  (the farthest brick from B 0  adjacent to column C 0 ) and R 7 C 1  (the farthest brick from B 0  adjacent to column C 1 ). 
       FIG. 2   a  illustrates a side view of a portion of exemplary touch sensor panel  200  showing the coupling between connecting traces  204  and bus lines  210  according to embodiments of the invention. In  FIG. 2   a , bus lines  210  and pads  218  (e.g. metal having a resistance of 1 ohm per square maximum) can be formed on substrate  220  (e.g. glass having a thickness of 500 microns+/−50 microns). Insulating layer  214  (e.g. organic polymer having a thickness of 3 microns minimum) can then be formed over bus lines  210  and pads  218  and patterned to create vias  216 . Connecting traces  204  can then be formed over insulating layer  214  and into vias  216  to make connections between the traces and bus lines  210 . In addition, the same conductive material used to form connecting traces  204  can also be partially formed over pads  218  at location  222  to protect the pads. On the back side of substrate  220 , conductive shield layer  224  (e.g. ITO having a thickness of 50 microns+/−10 microns) can be formed over substrate  220  to shield the sense lines (not shown in  FIG. 2   a ). Anti-reflective (AR) film  226  having a particular thickness (e.g. 75 microns+/−15 microns) can then be affixed to shield layer  224  using an adhesive such as a 25 micron layer of PSA. Flex circuit  212  can be attached to both the top and bottom of touch sensor panel  200  using an adhesive  228  (e.g. anisotropic conductive film (ACF)) capable of forming conductive bonds. Finally, touch sensor panel  200  can be bonded to cover material  230  (e.g. glass having a thickness of 800 to 1100 microns) using adhesive  232  (e.g. low-acid pressure sensitive adhesive (PSA) having a thickness of 150 microns+/−25 microns). 
       FIG. 2   b  illustrates a top view of a portion of the exemplary bus lines  210  of  FIG. 2   a  according to embodiments of the invention. Note that in the example of  FIG. 2   b , the top bus line is wider (e.g. 100 microns) at the point at which via 216 provides for a connection between bus line  210  and a connecting trace. 
     Referring again to the example of  FIG. 1   c , because bus line B 0  has much shorter connecting traces  104  to bricks R 0 C 0  and R 0 C 1  as compared to bus line B 7  (and its connecting traces to bricks R 7 C 0  and R 7 C 1 ), the impedance and capacitance of bus line B 7  can be much greater than that of bus line B 0 . Because of this imbalance, touch measurements for a given amount of touch may not be equalized across the touch sensor panel. Therefore, in some embodiments of the invention, the bricks coupled to a particular bus line can be interleaved so that each bus line sees a more uniform average impedance and capacitance, which can help equalize touch measurements across the touch sensor panel. 
       FIG. 3  illustrates a portion of exemplary touch sensor panel  300  including drive (or sense) lines formed as bricks  302  whose connecting traces  304  are interleaved according to embodiments of the invention. In the example of  FIG. 3 , which is drawn in a symbolic manner and not to scale for purposes of clarity, bus line B 0  is coupled to brick R 0 C 0  (the closest brick to B 0  adjacent to column C 0 ) and R 7 C 1  (the farthest brick from B 0  adjacent to column C 1 ). Bus line B 1  is coupled to brick R 1 C 0  (the next closest brick to B 0  adjacent to column C 0 ) and R 6 C 1  (the next farthest brick from B 0  adjacent to column C 1 ). This coupling pattern repeats for the other bus lines, as evidenced by bus line B 7  coupled to brick R 7 C 0  (the farthest brick from B 0  adjacent to column C 0 ) and R 0 C 1  (the closest brick to B 0  adjacent to column C 1 ). By interleaving the bricks coupled to any particular bus line as described above, each bus line sees a more uniform average impedance and capacitance, which can help equalize touch measurements across the touch sensor panel. However, it should be understood that with this arrangement, for a given bus line, the location of the bricks being stimulated can vary greatly. Nevertheless, post-processing of the resultant touch image can identify the actual touch locations. 
     Interleaving can additionally provide increased power uniformity. Without interleaving, some drivers can have a small capacitive load, while others can have a large capacitive load. To ensure that the largest load can be properly driven, all drivers may be designed to drive the largest capacitive load, resulting in higher current requirements for all drivers, even those not driven with a large load. However, with interleaving, each driver can have a more moderate and roughly equivalent capacitive load, and the drivers need only be designed to drive the moderate capacitive load. 
       FIG. 4   a  illustrates exemplary touch sensor panel  400  including sense (or drive) lines formed as columns  406 , drive (or sense) lines formed as rows of bricks  402 , and connecting traces  404  (illustrated symbolically as thin lines) routed along both sides of the bricks (a so-called “double escape” configuration) according to embodiments of the invention. In the example of  FIG. 4   a , sense (or drive) lines (C 0 -C 3 ) can be formed as columns  406  and drive (or sense) lines (R 0 -R 7 ) can be formed as rows of bricks  402 , where each row of bricks forms a separate drive (or sense) line. Although a touch sensor panel  400  having four columns and eight rows is shown, it should be understood that any number of columns and rows can be employed. Columns  406  and bricks  402  of  FIG. 4   a  can be formed in a co-planar single layer of conductive material. 
     To couple bricks  402  in a particular row together, connecting traces  404 , which are also formed from a conductive material, can be routed from the bricks along alternating sides of the bricks in a double escape configuration to a particular lower bus line  410  or upper bus line  414  (although it should be understood that in other embodiments, only a single group of bus lines at either the top or bottom may be employed). Ground guards  416 , which are formed from conductive material, can be formed between connecting traces  404  and adjacent columns  406 . Lower bus lines  410  and upper bus lines  414 , as well as connecting traces for columns  406 , can be routed along the border areas and brought off touch sensor panel  400  through a flex circuit. 
       FIG. 4   b  illustrates a close-up view of a portion of the exemplary touch sensor panel  400  of  FIG. 4   a , showing how bricks  402  can be routed to lower bus lines  410  using connecting traces  404  in a double escape configuration according to embodiments of the invention. In the example of  FIG. 4   b , connecting trace  404 -R 0 -E can be routed directly to lower bus lines  410 , connecting trace  404 -R 1 -E can be routed along the right side of brick R 0 -E, connecting trace  404 -R 2 -E can be routed along the left side of bricks R 0 -E and R 1 -E, and connecting trace  404 -R 3 -E can be routed along the right side of bricks R 0 -E, R 1 -E and R 2 -E (not shown) in the double escape configuration. 
     In the mutual capacitance double escape embodiment of  FIG. 4   b , each pixel can be characterized by the mutual capacitance between a column and two adjacent bricks. For example, the pixel or sensor for R 0 -C 3  can be formed by mutual capacitance  418  between brick R 0 -D and C 3 , and also mutual capacitance  420  between brick R 0 -E and C 3 . 
     As mentioned above, an optional ground guard can be formed around each column in  FIGS. 4   a  and  4   b , and can also be formed around each column in  FIGS. 1   a ,  1   b ,  1   c  and  3 . In one embodiment, the columns can be around 1000 microns wide, and the ground guard can be around 250 microns wide. One benefit of using a ground guard is improving the touch event detection capabilities of the touch sensor panel. 
       FIGS. 5   a  and  5   b  illustrate top and side views of the effect of exemplary ground guard  500  on polygonal area of conductive material  502  according to embodiments of the invention. 
       FIG. 5   a  illustrates an example without a ground guard. When either polygonal area of conductive material  502  or column  504  is driven by a stimulation signal, fringing electric field lines  506  appear between the polygonal area and column  504 . As the side view illustrates, some electric field lines can temporarily exit cover glass  508  in the process. Electric field lines  506  include near field lines  510 , which generally do not exit cover glass  508  and are therefore largely unaffected by a finger appearing on or in proximity to the cover glass. For example, near field lines  510  may generate a stray capacitance, Csig, of about 2.4 pF, but the change in the stray capacitance during a touch event, ΔCsig, may be only about 0.05 pf, which is a small change of about 2%. Electric field lines  506  also include far field lines  512 , some of which can temporarily exit cover glass  506  and can be blocked by a finger. In contrast to near field lines  510 , far field lines  512  may generate Csig of about 0.6 pF, but experience a change in the stray capacitance during a touch event, ΔCsig, of about 0.3 pF, which is a much larger change of about 50%. This large change represents a better signal-to-noise ratio (SNR) and improved touch event detection. 
     However, because both near and far field lines  510  and  512  are present when either polygonal conductive area  502  or column  504  is being stimulated, the total Csig being generated in the example above is about 3.0 pF and the total change in the stray capacitance ΔCsig during a touch event is about 0.35 pf, which represents only about a 10% change. To maximize the percentage change in stray capacitance during a touch event, it is desirable to minimize the amount of mutual capacitance that is unaffected by a touch event (i.e. near field lines  510 ), and instead rely as much as possible on the mutual capacitance that is changed by the touch event (i.e. far field lines  512 ). 
       FIG. 5   b  illustrates an example with ground guard  500 . As  FIG. 5   b  illustrates, ground guard  500  can reduce the undesirable mutual capacitance between the drive and sense lines by shunting most near field lines  510  directly to ground instead of allowing them to couple to sense line  504 , leaving mostly far field lines  512  affected by touch events. With mostly far field lines  512  affecting the mutual capacitance value, the change in capacitance during a touch event can approach 50% as discussed above, which represents an improved SNR. 
       FIGS. 5   c  and  5   d  illustrate top and side views of the effect of exemplary ground guard  500  on connecting trace  514  according to embodiments of the invention.  FIG. 5   c  illustrates an example without a ground guard. Because connecting trace  514  can be coupled to a polygonal conductive area, it too can be driven with a stimulation signal. Without a ground guard, as illustrated in  FIG. 5   c , near field lines  510  can couple onto adjacent sense line  504 , causing unintended changes in capacitance on the sense line. However, with a ground guard  500  in place as shown in  FIG. 5   d , near field lines  510  can be shunted to the ground guard instead of sense line  504 , decreasing the unintended change in capacitance on the sense line. 
       FIGS. 5   e  and  5   f  illustrate top and side views of the effect of exemplary ground guard  500  on polygonal conductive area  502  separated from sense line  504  by connecting traces  514  according to embodiments of the invention. Without a ground guard, as illustrated in  FIG. 5   e , near field lines  510  can couple onto sense line  504 , reducing the percentage change in capacitance on the sense line when a touch event occurs. However, with a ground guard  500  in place as shown in  FIG. 5   f , near field lines  510  can be shunted to the ground guard instead of sense line  504 , leaving mostly far field lines  512  affected by touch events, increasing the percentage change in capacitance on the sense line when a touch event occurs. 
     Referring again to  FIG. 1   a , the previously mentioned ground isolation bars can minimize the amount of stray capacitance, Csig, between the connecting traces and the sense lines. Nevertheless, for the very longest routing traces, there can still be on the order of about 6 pF of Csig transferred from the connecting traces to the sense lines, which can reduce the dynamic range budget and can make calibration difficult. Because the stray capacitance from the connecting traces to sense lines is somewhat affected by a touch event, it can causes spatial cross-coupling in which a touch event in one region of the touch sensor panel additionally causes a decrease in the stray capacitance and an apparent (but false) touch event in remote areas of the panel. 
       FIG. 6  illustrates a portion of exemplary zig-zag double interpolated touch sensor panel  600  that can further reduce the stray capacitance between the connecting traces and the sense lines according to embodiments of the invention. In the example of  FIG. 6 , polygonal areas  602  representing the drive (or sense) lines are generally pentagonal in shape and staggered in orientation, with some of the polygonal areas near the end of the panel being cut-off pentagons. Sense (or drive) lines  604  are zig-zag shaped, with ground guards  606  between the sense (or drive) lines and pentagons  602 . All connecting traces  608  are routed in channels  610  between pentagons  602 . In mutual capacitance embodiments, each pixel or sensor is characterized by electric field lines  616  formed between a pentagon and an adjacent sense (or drive) line  604 . Because connecting traces  608  do not run alongside any sense (or drive) lines  604 , but instead run between pentagons  602 , the stray capacitance between connecting traces  608  and sense (or drive) lines  604  is minimized, and spatial cross-coupling is also minimized. Previously, the distance between connecting traces  608  and sense (or drive) lines  604  was only the width of ground guard  606 , but in the embodiment of  FIG. 6 , the distance is the width of the ground guard plus the width of pentagon  602  (which varies along the length of its shape). 
     As the example of  FIG. 6  indicates, the pentagons for row R 14  at an end of the touch sensor panel can be truncated. Accordingly, the calculated centroids of touch  612  for R 14  can be offset in the y-direction from their true position. In addition, the calculated centroids of touch for any two adjacent rows will be staggered (offset from each other) in the x-direction by an offset distance. However, this misalignment can be de-warped in a software algorithm to re-map the pixels and remove the distortion. 
     Although embodiments of the invention have been primarily described herein in terms of mutual capacitance touch sensor panels, it should be understood that embodiments of the invention are also applicable to self-capacitance touch sensor panels. In such an embodiment, a reference ground plane can be formed either on the back side of the substrate, or on the same side of the substrate as the polygonal areas and sense lines but separated from the polygonal areas and sense lines by a dielectric, or on a separate substrate. In a self-capacitance touch sensor panel, each pixel or sensor has a self-capacitance to the reference ground that can be changed due to the presence of a finger. 
       FIG. 7  illustrates exemplary computing system  700  that can include one or more of the embodiments of the invention described above. Computing system  700  can include one or more panel processors  702  and peripherals  704 , and panel subsystem  706 . Peripherals  704  can include, but are not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers and the like. Panel subsystem  706  can include, but is not limited to, one or more sense channels  708 , channel scan logic  710  and driver logic  714 . Channel scan logic  710  can access RAM  712 , autonomously read data from the sense channels and provide control for the sense channels. In addition, channel scan logic  710  can control driver logic  714  to generate stimulation signals  716  at various frequencies and phases that can be selectively applied to drive lines of touch sensor panel  724 . In some embodiments, panel subsystem  706 , panel processor  702  and peripherals  704  can be integrated into a single application specific integrated circuit (ASIC). 
     Touch sensor panel  724  can include a capacitive sensing medium having a plurality of drive lines and a plurality of sense lines, although other sensing media can also be used. In mutual capacitance embodiments, each intersection of drive and sense lines can represent a capacitive sensing node and can be viewed as picture element (pixel)  726 , which can be particularly useful when touch sensor panel  724  is viewed as capturing an “image” of touch. (In other words, after panel subsystem  706  has determined whether a touch event has been detected at each touch sensor in the touch sensor panel, the pattern of touch sensors in the multi-touch panel at which a touch event occurred can be viewed as an “image” of touch (e.g. a pattern of fingers touching the panel).) Each sense line of touch sensor panel  724  can be coupled to a sense channel  708  (also referred to herein as an event detection and demodulation circuit) in panel subsystem  706 . 
     Computing system  700  can also include host processor  728  for receiving outputs from panel processor  702  and performing actions based on the outputs that can include, but are not limited to, moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device coupled to the host device, answering a telephone call, placing a telephone call, terminating a telephone call, changing the volume or audio settings, storing information related to telephone communications such as addresses, frequently dialed numbers, received calls, missed calls, logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user&#39;s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, and/or the like. Host processor  728  can also perform additional functions that may not be related to panel processing, and can be coupled to program storage  732  and display device  730  such as an LCD display for providing a UI to a user of the device. Display device  730  together with touch sensor panel  724 , when located partially or entirely under the touch sensor panel, can form touch screen  718 . 
     Note that one or more of the functions described above can be performed by firmware stored in memory (e.g. one of the peripherals  704  in  FIG. 7 ) and executed by panel processor  702 , or stored in program storage  732  and executed by host processor  728 . The firmware can also be stored and/or transported within any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “computer-readable medium” can be any medium that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, a portable computer diskette (magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), an erasable programmable read-only memory (EPROM) (magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory such as compact flash cards, secured digital cards, USB memory devices, memory sticks, and the like. 
     The firmware can also be propagated within any transport medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “transport medium” can be any medium that can communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The transport readable medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
       FIG. 8   a  illustrates exemplary mobile telephone  836  that can include touch sensor panel  824  and display device  830 , the touch sensor panel having rows and columns formed as described above according to embodiments of the invention. 
       FIG. 8   b  illustrates exemplary digital media player  840  that can include touch sensor panel  824  and display device  830 , the touch sensor panel having rows and columns formed as described above according to embodiments of the invention. 
     The mobile telephone and media player of  FIGS. 8   a  and  8   b  can advantageously benefit from the touch sensor panel described above because the touch sensor panel can enable these devices to be more touch sensitive, thinner and less expensive, which are important consumer factors that can have a significant effect on consumer desirability and commercial success. 
     Although embodiments of this invention have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of embodiments of this invention as defined by the appended claims.

Metadata:
Filing Date: 20080425
Publication Date: 20131105
Grant Date: 20131105
Priority Date: 20080425
Inventors: HOTELLING STEVE PORTER
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0416", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0416", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 40793202