Touch screen and method of compensating for differences in routing trace path lengths

Touch sensitive input devices and routing trace configurations designed to reduce border dimensions of such devices are provided herein. The touch sensitive input devices include a touch panel having a plurality of transmit lines and a plurality of receive lines, which are arranged with the plurality of transmit lines in a grid pattern, such that a sense node is disposed on the touch panel at each intersection of the transmit and receive lines. More specifically, the touch panel includes a first subset of the transmit lines coupled to routing traces on only a first side of the touch panel, a second subset of the transmit lines coupled to routing traces on only a second side of the touch panel, and a third subset of the transmit lines coupled to routing traces on both the first side and the second side of the touch panel. Methods are provided herein for compensating for differences in routing trace path lengths, so as to provide accurate detection of touch event locations on the touch panel.

FIELD

This application relates to display devices, and more particularly to touch screen display devices (i.e., touch screens).

BACKGROUND

Information handling systems typically utilize a display device to provide visual output related to operations occurring within and/or being performed by the information handling system. Depending on the type of information handling system, the display device can be physically connected or affixed to the system, or may be communicatively connected to the system via one or more cables and/or intermediary components (e.g., a docking station). Some display devices include a touch sensitive input device that enables a user to provide input to the information handling system through direct interaction with the display device.

A display device including a touch sensitive display device is otherwise referred to as a touch screen display device, or simply a touch screen. As known in the art, a touch screen enables a user to provide input to, or interact with, the display device or the information handling system via touch events, which are detected by components of the touch sensitive input device at precise locations on the display screen. There are many different types of touch screen technology that use different methods of sensing touch events. Examples of touch screen technology include resistive touch screens, capacitive touch screens, surface acoustic wave (SAW) touch screens, infrared touch screens and optical touch screens.

FIG. 1is a graphical representation of a conventional touch screen display device (or simply “touch screen”)10comprising a display screen active area (AA)20for display images, video content and/or user interface components, and a bezel30surrounding the display screen active area. The bezel30provides structural support for the touch screen components and/or attaches to a support structure housing the touch screen components. In conventional touch screen display device10, bezel30comprises a relatively large width (BWLand BWR) on the left and right sides of the display screen active area (AA)20. In some cases, the width of the bezel30bordering the top and bottom sides of the display screen active area (AA)20may be similar to, or different than, the left and right sides of the device. In some cases, the width of the bezel30on one or more sides of the device may range between about 3 mm and about 15 mm.

In order to sense touch events, touch screen10may include a touch sensitive input device comprising a touch sensor panel (or simply “touch panel”)40, which is arranged beneath the display screen active area20. The touch panel40is shown with dotted lines inFIG. 1to show that it resides behind the display screen of the display device10. In some cases, touch panel40may extend beyond the display screen active area (AA)20, so as to avoid dead spots on or near borders of the touch screen display device10.

FIG. 2is a graphical representation of an exemplary touch panel40that may be used within the conventional touch screen display device10ofFIG. 1. As shown inFIG. 2, touch panel40includes a plurality of transmit lines (or drive lines)50and a plurality of receive lines (or sense lines)60. The plurality of receive60lines are arranged at an angle (e.g., 90°) to, and intersect with, the plurality of transmit lines50to form a plurality of sense nodes70. In order to detect the presence of a finger or other object on or near one or more of the sense nodes70, a drive signal may be supplied to one or more of the transmit lines50via routing traces80/85on the left and right sides of the touch panel40. When a user touches a particular location on the display screen, a touch signal may be induced across one or more of the sense nodes70and forwarded to the touch sensitive input device via routing traces90.

InFIG. 2, the plurality of transmit lines50are coupled to routing traces80and85on both the left and right sides of the touch panel40. This type of routing configuration is referred to as a double routing trace configuration, and is commonly used in touch screen display devices, such as the touch screen10shown inFIG. 1. Because this type of routing configuration requires N routing traces on the left and right sides of the touch panel for N transmit lines50, the double routing trace configuration shown inFIG. 2consumes a significant amount of board space on either side of touch panel40. The amount of board space consumed by the left routing traces80, right routing traces85and ground ring87generally depends on the number (N) of transmit lines50, and is illustrated inFIG. 2as a left trace width (TWL) and a right trace width (TWR). In other cases (not shown), the plurality of transmit lines50may be coupled to routing traces (e.g., routing traces80) on only one side of the touch panel40in a single routing trace configuration. However, this routing configuration still consumes a significant amount of board space by requiring N routing traces on the left (or right) side of the touch panel40.

A current design trend in touch screen display devices is to reduce the border dimensions of such devices, and extend the active area of the display screen further out toward one or more edges of the display device. However, reducing border dimensions of touch screen display devices limits the available board space for routing traces from the touch panel of the display device.

SUMMARY

The following description of various embodiments of touch sensitive input devices, information handling systems and related methods is not to be construed in any way as limiting the subject matter of the appended claims.

Generally speaking, the present disclosure provides touch sensitive input devices (e.g., touch screen display devices, or touch screens), touch panels with routing trace configurations designed to reduce border dimensions of touch screen display devices, and related methods for compensating for differences in routing trace path lengths.

More specifically, the present disclosure provides an improved routing trace configuration that may be used to reduce the routing trace width on opposing sides (e.g., left and right sides, or top and bottom sides) of a touch panel of the touch sensitive input device. In addition, the present disclosure provides improved touch sensitive input devices, information handling systems and related methods, which provide accurate detection of touch event locations on the touch panel by compensating for differences in routing trace path lengths.

According to one embodiment, a touch sensitive input device according to the present disclosure may include a touch panel comprising a plurality of transmit lines and a plurality of receive lines, which are arranged with the plurality of transmit lines in a grid pattern, such that a sense node is disposed on the touch panel at each intersection of the transmit and receive lines. As described in more detail below, the touch sensitive input device may also generally include transmit circuitry, receive circuitry, a storage medium and a processing device. Although other components not specifically mentioned herein may be included within the touch sensitive input device, they are omitted from the present disclosure for purposes of brevity.

In one embodiment of the touch panel disclosed herein, a first subset of the transmit lines may be coupled to routing traces on only a first side (e.g., a left side) of the touch panel, a second subset of the transmit lines may be coupled to routing traces on only a second side (e.g., a right side) of the touch panel, and a third subset of the transmit lines may be coupled to routing traces on both the first side and the second side of the touch panel. The third subset of the transmit lines may be disposed on the touch panel between the first and second subsets of the plurality of transmit lines. In some embodiments, the plurality of receive lines may be coupled to routing traces on a third side (e.g., a bottom side or a top side) of the touch panel.

As noted above, the touch sensitive input device may include transmit circuitry and receive circuitry and a storage medium. In one embodiment, the transmit circuitry may be coupled to supply drive signals to the plurality of transmit lines via the routing traces on the first side and the second side of the touch panel, and the receive circuitry may be coupled to receive analog sense signals corresponding to each sense node on the touch panel from the routing traces on the third side of the touch panel. The receive circuitry may be generally configured to convert the analog sense signals into digital sense signals.

As noted above, the touch sensitive input device may include a storage medium and a processing device. In one embodiment, the storage medium may be coupled to the receive circuitry, and may be configured to store the digital sense signals generated by the receive circuitry in a memory table having rows and columns. In one embodiment, the memory table may include a first subset of rows containing digital sense signals corresponding to the first subset of transmit lines, a second subset of rows containing digital sense signals corresponding to the second subset of transmit lines, and a third subset of rows containing digital sense signals corresponding to the third subset of transmit lines. The processing device may be coupled to the storage medium, and may be generally configured to execute program instructions to compensate for offsets in the digital sense signals stored within the first and second subsets of the rows in the memory table.

In one embodiment, the program instructions may include at least a first set of program instructions, a second set of program instructions and a third set of program instructions. The first set of program instructions may be executable by the processing device to determine a first offset value by determining a difference between an average value of the digital sense signals stored within the first subset of rows and an average value of the digital sense signals stored within the third subset of rows. The second set of program instructions may be executable by the processing device to determine a second offset value by determining a difference between an average value of the digital sense signals stored within the second subset of rows and the average value of the digital sense signals stored within the third subset of rows. The third set of program instructions may be executable by the processing device to compensate for offsets in the digital sense signals stored within the first and second subsets of rows in the memory table by: (a) applying the first offset value to each of the digital sense signals stored within the first subset of rows, and (b) applying the second offset value to each of the digital sense signals stored within the second subset of rows.

According to another embodiment, a method is provided herein for determining a location of a touch event on a touch panel of a touch sensitive input device. In some embodiments, the method may begin by supplying drive signals to a plurality of transmit lines disposed on a touch panel, and receiving sense signals from a plurality of receive lines disposed on the touch panel in response thereto. After digitizing the received sense signals, the method may store the digital sense signals (at least temporarily) in a memory table having rows and columns. In some embodiments, the step of storing the digital sense signals may include: (a) storing digital sense signals corresponding to a first subset of the transmit lines, which are coupled to routing traces on only a first side of the touch panel, within a first subset of the N rows in the memory table; (b) storing digital sense signals corresponding to a second subset of the transmit lines, which are coupled to routing traces on only a second side of the touch panel, within a second subset of the N rows in the memory table; and (c) storing digital sense signals corresponding to a third subset of transmit lines, which are coupled to routing traces on both the first side and the second side of the touch panel, within a third subset of the N rows in the memory table.

Next, the method may adjust the digital sense signal values stored within the memory table by determining a first offset value, determining a second offset value, and respectively applying the first and second offset values to the each of the digital signal values stored within the first and second subsets of rows in the memory table.

In some embodiments, the first offset value may be determined by determining a difference between an average value of the digital signals stored within the first subset of rows and an average value of the digital signals stored within the third subset of rows. In some embodiments, the second offset value may be determined by determining a difference between an average value of the digital signals stored within the second subset of rows and an average value of the digital signals stored within the third subset of rows.

In some embodiments, the digital sense signal values stored within the memory table may be adjusted by applying the first offset value to each of the digital signals stored within the first subset of the rows in the memory table, and by applying the second offset value to each of the digital signals stored within a second subset of the rows in the memory table. The second offset value may generally by different from the first offset value, due to the path length differences for the sense nodes associated with the second subset of transmit lines compared to the sense nodes associated with the first subset of transmit line.

In some embodiments, the method may use the adjusted digital sense signals to detect a location of a touch event on the touch panel. By respectively applying the first and second offset values to the digital sense signal values stored within the first and second subsets of the rows, the adjusted digital sense signal values become much more uniform, thereby enabling the location of the touch event on the touch panel to be detected with significantly greater accuracy.

According to another embodiment, an information handling system including a touch panel and a touch controller is provided herein. The touch panel may be configured, as generally described above. The touch controller may be coupled to the touch panel for supplying drive signals to the plurality of transmit lines, receiving sense signals corresponding to the sense nodes from the plurality of receive lines, digitizing the received sense signals and storing the digital sense signals. In addition, the touch controller may be configured to compensate for offsets in the digital sense signals corresponding to sense nodes associated with a first subset of the plurality of transmit lines and the digital sense signals corresponding to sense nodes associated with a second subset of the plurality of transmit lines. The touch controller may include transmit circuitry, receive circuitry, a storage medium and a processing device, as generally described above.

While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form disclosed, but on the contrary, the present disclosure is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As noted above, this disclosure generally relates to touch sensitive input devices, routing trace configurations designed to reduce border dimensions of such devices, and related methods for compensating for offsets in touch signals due to differences in routing trace path lengths. In some embodiments, the touch sensitive input devices described herein may be part of, or configured for use with, a variety of different information handling systems.

With reference now toFIG. 3, there is depicted a block diagram representing a generalized embodiment of an information handling system100comprising and/or communicatively coupled to a display device200. As depicted inFIG. 3, information handling system100may generally include one or more information handling resources. The information handling resources may include any component, system, device or apparatus of information handling system100, including without limitation processors, busses, computer-readable media, input-output devices and/or interfaces, storage resources, network interfaces, motherboards, electro-mechanical devices (e.g., fans), and/or power supplies.

In the generalized embodiment shown inFIG. 3, information handling system100includes at least one central processing unit (CPU)110, which is coupled to system memory120via system interconnect130(otherwise referred to as a system bus). Also coupled to CPU110, via system interconnect130, is a graphics card with a graphics processing unit (GPU)140located thereon, nonvolatile storage (NVRAM)150, and one or more input/output devices160. Input/output devices160may include, but are certainly not limited to, keyboards, mice, touch pads, speakers, and cameras.

Information handling system100requires a power source to operate the various electronic components disposed therein. The power source can be provided via an external power source (e.g., mains power) and an internal power supply regulator, and/or by an internal power source, such as a battery. As shown inFIG. 3, power management system170may be included within information handling system100for moderating the available power from the power source. The power management system170may be coupled to one or more components of the information handling system100via a power bus135to provide the required power, as well as to perform other power-related administrative tasks of the information handling system.

System memory120and/or NVRAM150may be generally configured to store software and/or firmware modules and one or more sets of data that can be utilized during operation of information handling system100. In some embodiments, one or more of these software and/or firmware modules can be loaded into system memory120from NVRAM150during operation of system100. In one embodiment, system memory120may include, or may be loaded with, a plurality of such modules, including one or more firmware (FW) modules, a basic input/output system (BIOS), an operating system (OS), and one or more user application(s). These software and/or firmware modules have varying functionality when their corresponding program code is executed by a main processing device (e.g., CPU110) or a secondary processing device (e.g., GPU140) of information handling system100.

As noted above, information handling system100also includes a display device200, which may be a part of, or communicatively coupled to, the information handling system100. For example, display device200may be permanently or detachably affixed to the information handling system100, when system100is a laptop computer, tablet computer, e-reader, “2 in 1” system or a mobile device (e.g., PDA or smart phone). Alternatively, display device200may be a stand-alone display device, which is communicatively coupled to information handling system100via one or more cables and/or other interfaces (e.g., a docking station), when system100is a desktop computer. Regardless of whether the display device is a stand-alone device, or integrated with the information handling system100, display device200may be coupled to receive and/or transmit data signals from/to a processing device (e.g., CPU110or GPU140) of system110, and may be further coupled to receive power from the power management system170within system100.

Generally speaking, display device200may be any type dynamic display capable of displaying images, video content and/or graphical user interfaces on a display screen of the display device, and may include any type of light emitting diode (LED), organic LED (OLED), liquid crystal display (LCD), electroluminescence (EL) or other display technology. Of the various types of display devices that can be provided with different information handling systems, perhaps the most common type of display device in use today is a liquid crystal display (LCD) device.

An LCD device generally includes an LCD panel comprising a layer of liquid crystals sandwiched between an upper and lower glass substrate, a color filter formed upon the upper glass substrate of the LCD panel to provide a pattern of red, green and blue (RGB) pixels, a vertically polarizing film overlaying the color filter to polarize light entering the display device, and a horizontally polarizing film formed upon the lower glass substrate to block/pass light. Since the LCD panel produces no light of its own, a backlight panel is used to illuminate the RGB pixels and create an image on a display screen of the LCD device. In some embodiments, the backlight panel may comprise an array of light sources (e.g., an array of cold cathode fluorescent lamps, CCFLs, LEDs or OLEDs) and a diffuser panel, which are positioned behind the LCD panel for providing evenly diffused illumination to the LCD panel. In other embodiments, the backlight panel may include light sources (e.g., CCFLs, LEDs or OLEDs) along two or more side edges of the display device that are positioned for emitting light into a light guide plate (LGP) or diffuser panel. The LGP and edge-mounted light sources may be arranged behind the LCD panel for providing evenly diffused illumination thereto.

Regardless of the type of display technology used (e.g., LCD, LED, OLED, EL, etc.), display device200preferably includes a touch sensitive input device that enables a user to provide input to the information handling system100through direct interaction with the display device. As noted above, a display device comprising a touch sensitive input device (i.e., a touch screen display device, or simply “touch screen”) enables a user to provide input to, or interact with, display device200or information handling system100via touch events, which are detected by components of the touch sensitive input device at precise locations on the touch screen.

FIG. 4is a graphical representation of a touch screen display device210comprising a display screen active area (AA)220for display images, video content and/or user interface components, a bezel230surrounding the display screen active area220, and a touch sensitive input device comprising a touch sensor panel (or simply “touch panel”)240that overlaps at least part of the display screen active area220. Similar to bezel30, bezel230may provide structural support to the display device components and/or may attach to a support structure housing the display device components. Touch panel240is depicted with dotted lines inFIG. 4to show that it resides behind the display screen of the touch screen display device200. As described in more detail below with reference toFIG. 5, the presence of a finger (or other object) near touch panel240may enable the touch sensitive input device to detect a touch event at a precise location on the display screen. In some embodiments, touch panel240may encompass as much of the display screen active area220as possible, so as to avoid dead spots (i.e., locations where touch events cannot be detected) on or near borders of the display screen active area220.

As noted above, a current design trend in touch screen display devices is to reduce the border dimensions of such devices, and extend the active area of the display screen further out toward one or more edges of the display device. As shown by a comparison ofFIGS. 1 and 4, bezel230is depicted with a comparatively smaller width (BWLand BWR) on the left and right sides of display screen active area (AA)220than bezel30of touch screen display device10ofFIG. 1. In some embodiments, the width of the bezel230on the top and bottom of display device200may be similar to, or different than, the left and right sides of the device. In some embodiments, the width of the bezel230on one or more sides of the device may be about 3 mm or less.

Reducing the border dimensions of a touch screen display device, such as touch screen200, allows the display screen active area (AA)220to be extended further out toward edges of the display device, thereby resulting in a comparatively larger display screen without increasing the overall dimensions of the display device. In other words, although touch screen display devices100and200may be confined to the same width (W) and the same height (H), bezel230provides a substantially smaller border width (BWLand BWR) than bezel30, thus resulting in a comparatively larger display screen active area220. Unfortunately, reducing the border dimension(s) of a touch screen display device limits the board space available for routing traces from touch panel240to other components of the touch sensitive input device.

FIG. 5is a graphical representation of an exemplary touch panel240that may be used within the touch screen display device210ofFIG. 4. As shown inFIG. 5, touch panel240includes a plurality of transmit lines (or drive lines)250and a plurality of receive lines (or sense lines)260. According to one embodiment, transmit lines250and receive lines260may comprise a transparent conductive medium, such as Indium Tin Oxide (ITO) or Antimony Tin Oxide (ATO), formed on opposing sides of an insulating layer. Other transparent conductive mediums may be used in other embodiments.

As shown inFIG. 5, the plurality of receive lines260are arranged at an angle (e.g., 90°) to the plurality of transmit lines250, such that a sense node270is formed at the “intersection” of each transmit line250and receive line260. Although the transmit lines250and receive lines260are illustrated as straight lines inFIG. 5, it is understood that transmit lines250and/or receive lines260may be implemented with alternative geometries. It is further understood that although transmit lines250and receive lines260are depicted as being substantially perpendicular to each other, they may be arranged at angles other than 90°, as long as they “intersect” (i.e., cross over each other in vertically spaced planes) to form sense nodes270.

In order to detect the presence of a finger (or other object) near one or more of the sense nodes270, a drive signal is supplied to one or more of the transmit lines250via routing traces280/285on the left and right sides of the touch panel240, which causes a signal charge to be injected into the receive lines260and a capacitance (Csig) to be generated at each sense node270. The capacitance can appear as a stray capacitance when the transmit lines are held at direct current (DC) levels, and as a mutual signal capacitance when the transmit lines are stimulated with an alternating current (AC) signal. When a user touches a particular location on the display screen, a touch event may be detected at one or more of the sense nodes270by detecting a change in the signal charge caused by a change in the capacitance (Csig) induced across the sense nodes270. As described in more detail below, the signal charges injected into receive lines260may be forwarded to the touch sensitive input device via routing traces290as analog “sense signals.”

As noted above, the conventional double routing trace configuration shown inFIG. 2requires N number of routing traces on both the left and right sides of touch panel40for driving the same number (N) of transmit lines50. Because the relatively large trace width on the left and right sides (TWLand TWR) of touch panel40consumes a significant amount of board space, the conventional double trace routing configuration shown inFIG. 2cannot be used within touch screen display devices with reduced border dimensions, such as the display device210shown inFIG. 4. As such, an alternative routing trace configuration is needed for such devices.

FIG. 5illustrates one embodiment of an alternative routing trace configuration that may be used within a touch screen display device having reduced border dimensions. Unlike conventional routing methods, the routing trace configuration shown inFIG. 5combines both single routing and double routing methods on the same touch panel240to reduce the left and right trace widths (TWLand TWR) on the touch panel, thereby enabling smaller border dimensions (BWLand BWR) for the touch screen display device200. As described in more detail below, the routing trace configuration shown inFIG. 5significantly reduces the trace width on both the left and right sides (TWLand TWR) of touch panel240, compared to the conventional double routing trace configuration shown inFIG. 2.

In the exemplary embodiment shown inFIG. 5, a first subset252of the transmit lines250are coupled to routing traces280on only a first side of the touch panel240(e.g., to provide single routing to the first subset on the left side only), a second subset254of the transmit lines250are coupled to routing traces285on only a second side of the touch panel (e.g., to provide single routing to the second subset on the right side only), and a third subset256of the transmit lines250are coupled to routing traces280/285on both the first side and the second side of the touch panel240(e.g., to provide double routing to the third subset on both the left and right sides). The third subset256of the transmit lines250are preferably disposed on touch panel240between the first and second subsets252and254of the transmit lines for reasons discussed below. In some embodiments, receive lines260may be coupled to routing traces290on a third side (e.g., a bottom side or a top side) of the touch panel240. It is noted, however, that alternative routing configurations may be used for receive lines260. A ground ring287encircles a periphery of touch panel240and routing traces20/285, as shown inFIG. 5.

Although a particular number (e.g., 9) of transmit lines250and a particular number (e.g., 11) of receive lines260are illustrated inFIG. 5, it is noted that the figures are not drawn to scale; a reduced number of transmit and receive lines are shown merely for drawing clarity. Generally speaking, the number of transmit lines250and receive lines60included on touch panel240may depend on a variety of factors including, but not limited to, one or more dimensions (e.g., height and/or width) of the display screen active area (AA)220, desired touch screen sensitivity (e.g., a desired number of sense nodes270within AA220), trace width (e.g., the width of the transmit and receive lines) and trace pitch (e.g., the trace width plus the gap between the transmit and receive line traces). According to one particular embodiment, touch panel240may include 46 transmit lines and 72 receive lines for an exemplary display screen active area (AA)220height of about 15.6 inches, a trace width of about 20 μm and a trace pitch of about 45 μm. However, touch panel240is not restricted to such values, and may include a different number of transmit and receive lines in other embodiments.

To reduce the trace widths (TWLand TWR) on both the left and right sides of the touch panel240, one-half of the total number of transmit lines (e.g., first subset252) are coupled to routing traces on the left side of the touch panel240, while the other half (e.g., second subset254) is coupled to routing traces on the right side of the touch panel. In the example embodiment provided above, the first and second subsets252/254of transmit lines may each include 23 transmit lines to provide a total number of 46 transmit lines. As noted above, a third subset256of transmit lines disposed between the first and second subsets252and254is coupled to routing traces on both the right and left sides of the touch panel240. The third subset256of transmit lines may generally include one or more transmit lines. In one particular embodiment, the third subset256of transmit lines includes 3 transmit lines, although an alternative number of transmit lines may be used in other embodiments.

According to one embodiment, the routing method shown inFIG. 5may reduce the left and right side trace widths (TWLand TWR) each by approximately 0.9 mm for an exemplary display screen active area (AA)220height of about 15.6 inches, a total of 46 transmit lines, a trace width of about 20 μm and a trace pitch of about 45 μm. It should be understood that alternative left and right trace widths (TWLand TWR) can be achieved for other screen dimensions, number of transmit lines, trace widths and trace pitches using the routing method shown inFIG. 5. In some embodiments, a similar routing method may be used on the top and/or bottom sides of touch panel240to reduce the trace widths on the top and/or bottom sides.

As described in more detail below, the third subset256of transmit lines may be added to touch panel240to compensate for offsets in the sense signals detected from the touch panel due to differences in path lengths attributed to the routing traces280/285coupled to the first and second subsets252/254of transmit lines. As used herein, the path length is defined as the distance between a particular transmit channel and a particular receive channel of the touch sensitive input device.

Each sense node270on touch panel240has an inherently different path length, and thus, a different sense signal level associated therewith. However, due to the particular routing configuration shown inFIG. 5, sense nodes associated with the first subset252of transmit lines may have a significantly shorter path length than sense nodes associated with the second subset254of transmit lines. This path length difference may cause the receive circuitry of the touch sensitive input device to detect significantly smaller sense signals from sense nodes associated with the first subset252, compared to sense nodes associated with the second subset254of transmit lines. The opposite would be true, if the first subset252of transmit lines were coupled to routing traces on the right side, and the second subset254of transmit lines were coupled to routing traces on the left side of the touch panel240. As described in more detail below, the average sense signal level detected from the sense nodes associated with the third subset256of transmit lines may fall somewhere in between the average sense signal levels detected from the sense nodes associated with the first and second subsets252/254of transmit lines. The touch sensitive input device may use this information to adjust the sense signals detected from the sense nodes associated with the first and second subsets252/254of transmit lines to improve sense signal uniformity across all sense nodes270.

FIG. 6illustrates a block diagram of a display device200including exemplary components of a touch sensitive input device, such as touch panel240and touch controller300. Touch panel240utilizes a routing trace configuration, which combines both single routing and double routing methods on the same touch panel. Although a particular routing configuration is shown inFIG. 5, it is noted that other routing trace configurations, which combine single and double routing methods on the same touch panel may be used without departing from the scope of the present disclosure.

As shown inFIG. 6, touch controller300may generally include transmit (Tx) driver310, transmit circuitry320, receive (Rx) circuitry330, storage medium340and processing device350. The touch controller components shown inFIG. 6may be implemented in hardware, software, firmware or any combination thereof. According to one embodiment, touch controller300may be implemented as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a central processing unit (CPU) or another processing device. In some embodiments, touch controller300may comprise, or be configured to execute, software and/or firmware to perform one or more of the operations noted herein.

Transmit circuitry320may be coupled to the routing traces on the left and right sides of touch panel240for supplying the drive signals to the plurality of transmit lines. In some embodiments, transmit driver310may be included to generate the supply voltage for transmit circuitry320, and may be a charge pump, in one example. Although the transmit driver310is illustrated as a separate component inFIG. 6, the transmit driver310may be included within the transmit circuitry320in other embodiments. In general, the drive signals supplied to the plurality of transmit lines250by transmit circuitry320may comprise substantially any amplitude, frequency, phase, waveform or level. In some embodiments, substantially uniform drive signals may be supplied to all transmit lines. In other embodiments, the drive signals supplied to one or more of the transmit lines may differ in amplitude, frequency, phase, waveform and/or level. In some embodiments, processing device350may control the generation and/or application of the drive signals to the transmit lines.

FIG. 7illustrates a block diagram of transmit circuitry320, according to one embodiment. As shown inFIG. 7, transmit circuitry320may include transmit line scan circuitry322and digital to analog converter (DAC)324. Transmit line scan circuitry322is configured to generate the drive signals and to selectively apply the drive signals to one or more of the transmit lines. DAC324converts the digital drive signals generated by transmit line scan circuitry322into analog drive signals before they are selectively applied to the one or more of the transmit lines.

Receive circuitry330may be coupled to the routing traces on the bottom (and/or the top) of touch panel240for receiving the analog sense signals (e.g., charge signals) from the plurality of receive lines.FIG. 8illustrates a block diagram of receive circuitry330, according to one embodiment. As shown inFIG. 8, receive circuitry330may include a plurality of analog to digital converters (ADC)332, a digital signal processor (DSP)334, and a look up table (LUT)336, in one embodiment. The ADCs332may be generally configured for receiving the analog sense signals from routing traces290(see,FIG. 5) and for converting the analog sense signals into digital sense signals. The digital signal processor (DSP)334receives the digital sense signals from the ADCs332and determines average values for the digit sense signals corresponding to the sense nodes in the first, second and third subsets252/254/256of transmit lines. More specifically, DSP334may determine a first average value for the digit sense signals corresponding to the sense nodes in the first subset252of transmit lines, a second average value for the digit sense signals corresponding to the sense nodes in the second subset254of transmit lines, and a third average value for the digit sense signals corresponding to the sense nodes in the third subset256of transmit lines. The first, second and third average values may be stored in look up table (LUT)336and may be used to compensate for offsets in the digital sense signals corresponding to the sense nodes in the first subset252and second subset254of transmit lines, as discussed in more detail below. In some embodiments, processing device350may control the receipt of the analog sense signals and/or the generation of the digital sense signals.

In some embodiments, the digital sense signals generated by ADC332may be stored (at least temporarily) within storage medium340, which is coupled to receive circuitry330and processing device350. Although illustrated as a separate component of touch controller300inFIG. 6, storage medium340may alternatively be included within receive circuitry330or within processing device350. In general, storage medium340may be configured to store the digital sense signals in a memory table having rows and columns.FIG. 9illustrates one exemplary embodiment of such a memory table.

In one embodiment, storage medium340may include a memory table of N rows and M columns for storing N×M digital sense signals associated with the sense nodes of the touch panel. However, storage of the digital sense signals is not limited to a memory table. In other embodiments, the digital sense signals may be stored sequentially or randomly. InFIG. 9, memory table400is illustrated as having N=9 rows and M=11 columns for storing the N×M=99 digitals sense signals associated with sense nodes270of the touch panel240shown inFIG. 5. It is noted, however, that the number N of rows and the number M of columns depicted in memory table400has been reduced for purposes of drawing clarity. In general, the memory table will include the same number rows and columns as the number of transmit and receive lines included within the touch panel. In the example provided above, touch panel240may include 46 transmit lines and 72 receive lines, resulting in 3312 sense nodes. In such an example, the memory table may include 46 rows and 72 columns for storing 3312 digital sense signals corresponding to the 3312 sense nodes of the touch panel.

As shown inFIG. 9, the N rows of the memory table400may be divided into a first subset410, a second subset420and a third subset430of rows. The first subset410of rows includes digital sense signals corresponding to sense nodes associated with the first subset252of transmit lines250(see,FIG. 5). The second subset420of rows includes digital sense signals corresponding to sense nodes associated with the second subset254of transmit lines250. The third subset430of rows includes digital sense signals corresponding to sense nodes associated with the third subset256of transmit lines.

As shown inFIG. 9, the digital sense signals stored within the first subset410of rows include substantially smaller values (e.g., values ranging between about 4300 and about 4600, in one embodiment) than the values of the digital sense signals stored within the second subset420of rows (e.g., values ranging between about 4900 and about 5200, in one embodiment). This is due, at least in part, to the routing configuration shown inFIG. 5, which causes the sense nodes associated with the first subset252of transmit lines to have a significantly shorter path length than the sense nodes associated with the second subset254of transmit lines. On the other hand, the digital sense signals stored within the third subset430of rows include substantially larger values (e.g., values ranging between about 5300 and about 5600, in one embodiment) than the digital signals stored within the first subset410and the second subset420of rows. This is because the double routing method used for the third subset256of transmit lines increases the path length of the sense nodes associated with the third subset256of transmit lines.

According to one exemplary embodiment, a first average value of the digital sense signals stored within the first subset410of rows may be approximately 4400, a second average value of the digital sense signals stored within the second subset420of rows may be approximately 5000, and a third average value of the digital sense signals stored within the third subset430of rows may be approximately 5200. According to one embodiment, the first, second and third average values may be stored within LUT336, as shown inFIG. 8and described above. It is noted, however, that the first, second and third average values may not be stored within a LUT336of the receive circuitry350in all embodiments, and may be stored elsewhere or generated on the fly, in other embodiments. It is further noted the values of the digital sense signals shown inFIG. 9, and the average values thereof, are merely exemplary and used for illustrative purposes only. In some cases, the differences or offsets between the digital sense signal values stored within the first subset410and the second subset420of rows (e.g., an average offset value of approximately 600, in one embodiment) may cause the touch sensitive input device to incorrectly determine the location of a touch event on the touch panel240. As such, a method is needed to compensate for such offsets, so that the location of a touch event can be precisely determined.

As shown inFIG. 6, processing device350is coupled to storage medium340. According to one embodiment, processing device350may comprise, or be configured to execute, program instructions to implement a method to compensate for the offsets in the digital sense signal values stored within the first subset410and the second subset420of the rows in memory table400(or another memory table comprising N rows and M columns, as discussed above with respect toFIG. 5). One embodiment of such a method is depicted in steps640-670of the flow chart diagram shown inFIG. 11and described in more detail below.

According to one embodiment, processing device350may comprise, or be configured to execute, a first set of program instructions to determine a first offset value by determining a difference between an average value of the digital sense signals stored within the first subset410of rows (e.g., a first average value of about 4400) and an average value of the digital sense signals stored within the third subset430of rows (e.g., a third average value of about 5200). In the example provided above, the first offset value may be 5200−4400=800. Processing device350may further comprise, or be configured to execute, a second set of program instructions to determine a second offset value by determining a difference between an average value of the digital sense signals stored within the second subset420of rows (e.g., a second average value of about 5000) and the average value of the digital sense signals stored within the third subset430of rows (e.g., the third average value of about 5200). In the example provided above, the second offset value may be 5200−5000=200.

Once the first and second offset values are determined, processing device350may comprise, or be configured to execute, a third set of program instructions to adjust the values of the digital sense signals stored within the first and second subsets410/420of rows in the memory table by applying (e.g., adding) the first offset value (e.g., 800) to each of the digital sense signal values stored within the first subset410of rows, and applying the second offset value (e.g., 200) to each of the digital sense signal values stored within the second subset420of rows. In some embodiments, the adjusted digital sense signal values may be updated within memory table400, or may be stored (at least temporarily) within another memory table within storage medium340.FIG. 10illustrates one exemplary embodiment of such a memory table.

Like memory table400ofFIG. 9, memory table500ofFIG. 10may generally include N rows and M columns for storing the N×M digital sense signals associated with the sense nodes of the touch panel. Although illustrated inFIG. 10as having N=9 rows and M=11 columns for storing N×M=99 digitals sense signals associated with the sense nodes270of the touch panel240shown inFIG. 5, memory table500is not restricted to such an implementation, and will generally include the same number rows and columns as the number of transmit and receive lines included within the touch panel.

As shown inFIG. 10, the adjusted digital sense signal values stored within memory table500are significantly more uniform than the digital sense signal values stored within memory table400. According to one embodiment, the average value of the digital sense signals stored within the first subset410, the second subset420and the third subset430of rows may be approximately 5200. In some embodiments, processing device350may be further configured to execute program instructions to detect a location of a touch event on the touch panel based on the adjusted digital sense signal values stored within memory table500. Because the adjusted digital sense signal values stored within memory table500are relatively uniform across all sense nodes, the location of the touch event can be more accurately determined.

According to one embodiment, the compensation method performed by processing device350may be embodied, at least in part, in a computer readable storage medium containing computer readable code, such that a series of steps are performed when the computer readable code is executed on the processing device. The computer readable storage medium may be storage medium340, or another storage medium included within touch controller300, display device200or information handling system100. The computer readable storage medium may be implemented as substantially any non-transitory computer readable storage medium, including but not limited to, a direct access storage device (e.g., a hard disk drive), random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), and/or flash memory. The computer readable code, or program instructions, used to implement the compensation method described herein may be written in any combination of one or more programming languages, including an object oriented programming language, without limitation.

In some embodiments, the computer program instructions may be provided to processing device350of touch controller300for execution, as set forth above. In other embodiments, the computer program instructions may instead be provided to a processing device of display device200(such as a display controller or other host processor), a processing device of information handling system100(such as a display controller, a central processing unit, CPU, or a graphics processing unit, GPU), or another programmable data processing apparatus to produce a machine, such that the program instructions, which execute via the processing device of the display device or information handling system, performs the methods described herein.

FIG. 11illustrates one embodiment of a method600that may be performed by the touch sensitive input device shown inFIG. 6to determine a location of a touch event on a touch panel of the touch sensitive input device. Although all method steps shown inFIG. 11are performed in at least one embodiment, the touch sensitive input device shown inFIG. 6may not perform all method steps in all embodiments; moreover, fewer, additional and/or alternative steps may be performed in other embodiments. In some embodiments, one or more of the method steps shown inFIG. 11may be performed by, or under the control of, other components of display device200or information handling system100.

According to one embodiment, method600may begin in step610by supplying drive signals to a plurality of transmit lines disposed on a touch panel, such as transmit lines250of the touch panel240shown inFIG. 5. In one embodiment, transmit circuitry320of touch controller300may be configured to supply the drive signals to the plurality of transmit lines in step610via routing traces280/285. As noted above, the drive signals may comprise substantially any amplitude, frequency, phase, waveform or level.

In step620, method600may receive sense signals from a plurality of receive lines disposed on the touch panel, such as receive lines260of the touch panel240shown inFIG. 5. As noted above, a signal charge may be injected into the receive lines260and a capacitance (Csig) may be generated at each sense node270when drive signals are supplied to the transmit lines250. The signal charges injected into the receive lines260may be forwarded to the touch sensitive input device via routing traces290as analog “sense signals.”

In step630, method600may digitize the received sense signals and store the digital sense signals (at least temporarily) in a memory table having rows and columns, such as memory table400ofFIG. 9. As noted above, the memory table may generally include N rows and M columns for storing N×M digital sense signals associated with the sense nodes of a touch panel. In some embodiments, step630may include: (a) storing digital sense signals corresponding to a first subset of the transmit lines (e.g., first subset252of transmit lines,FIG. 5), which are coupled to routing traces on only a first side of the touch panel, within a first subset of the N rows in the memory table (e.g., first subset410of rows,FIG. 9); (b) storing digital sense signals corresponding to a second subset of the transmit lines (e.g., second subset254of transmit lines,FIG. 5), which are coupled to routing traces on only a second side of the touch panel, within a second subset of the N rows in the memory table (e.g., second subset420of rows,FIG. 9); and (c) storing digital sense signals corresponding to a third subset of transmit lines (e.g., third subset256of transmit lines,FIG. 5), which are coupled to routing traces on both the first side and the second side of the touch panel, within a third subset of the N rows in the memory table (e.g., third subset430of rows,FIG. 9).

In steps640-660, method600may adjust the digital sense signal values stored in the memory table by determining a first offset value in step640, determining a second offset value in step650, and respectively applying the first and second offset values to the each of the digital signal values stored within the first and second subsets of rows in the memory table in step660.

In some embodiments, the first offset value may be determined in step640by determining a difference between a first average value of the digital signals stored within the first subset of rows and a third average value of the digital signals stored within the third subset of rows. In the example provided above, the first offset value was determined to be 5200−4400=800.

In some embodiments, the second offset value may be determined in step650by determining a difference between a second average value of the digital signals stored within the second subset of rows and the third average value of the digital signals stored within the third subset of rows. In the example provided above, the second offset value was determined to be 5200−5000=200.

In some embodiments, the digital sense signal values stored within the memory table may be adjusted in step660by applying the first offset value (e.g., 800) to each of the digital signals stored within the first subset of the rows in the memory table (e.g., first subset410of rows,FIG. 9), and by applying the second offset value (e.g., 200) to each of the digital signals stored within a second subset of the rows in the memory table (e.g., second subset420of rows,FIG. 9). The second offset value will generally be different from the first offset value, due to the path length differences for the sense nodes associated with the second subset of transmit lines compared to the sense nodes associated with the first subset of transmit lines.

In step670, method600may use the adjusted digital sense signals to detect a location of a touch event on the touch panel. By respectively applying the first and second offset values to the digital sense signal values stored within the first and second subsets of the rows in step660, the adjusted digital sense signal values become much more uniform, thereby enabling the location of the touch event on the touch panel to be detected with significantly greater accuracy.

While the present disclosure may be adaptable to various modifications and alternative forms, specific embodiments have been shown by way of example and described herein. However, it should be understood that the present disclosure is not intended to be limited to the particular touch sensitive input device, display device, information handling system and/or methods disclosed and illustrated herein. Rather, the present disclosure is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

In some implementations, certain steps of the methods described herein may be combined, performed simultaneously or in a different order, or perhaps omitted, without deviating from the scope of the disclosure. Thus, while the method steps are described and illustrated in a particular sequence, use of a specific sequence of steps is not meant to imply any limitations on the disclosure. Changes may be made with regards to the sequence of steps without departing from the spirit or scope of the present disclosure. Use of a particular sequence of steps is therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined only by the appended claims. Furthermore, certain changes may be made with regard to the touch sensitive input device, display device and/or the information handling system without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not limited to only those embodiments shown and described herein, and may include other embodiments and/or combinations of embodiments.