Patent Publication Number: US-10331255-B2

Title: Integrated pixel display and touch sensor

Description:
RELATED APPLICATION 
     This application claims the benefit, under 35 U.S.C. § 120, as a divisional of U.S. patent application Ser. No. 14/983,064, filed Dec. 29, 2015, entitled Integrated Pixel Display and Touch Sensor, incorporated herein by reference, which is a divisional under 35 U.S.C. § 120 of U.S. patent application Ser. No. 13/715,677, filed Dec. 14, 2012 and entitled Integrated Pixel Display and Touch Sensor, incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure generally relates to integrated pixel displays and touch sensors. 
     BACKGROUND 
     A touch sensor may detect the presence and location of a touch or the proximity of an object (such as a user&#39;s finger or a stylus) within a touch-sensitive area of the touch sensor overlaid on a display screen, for example. In a touch-sensitive-display application, the touch sensor may enable a user to interact directly with what is displayed on the screen, rather than indirectly with a mouse or touch pad. A touch sensor may be attached to or provided as part of a desktop computer, laptop computer, tablet computer, personal digital assistant (PDA), smartphone, satellite navigation device, portable media player, portable game console, kiosk computer, point-of-sale device, or other suitable device. A control panel on a household or other appliance may include a touch sensor. 
     There are a number of different types of touch sensors, such as (for example) resistive touch screens, surface acoustic wave touch screens, and capacitive touch screens. Herein, reference to a touch sensor may encompass a touch screen, and vice versa, where appropriate. When an object touches or comes within proximity of the surface of the capacitive touch screen, a change in capacitance may occur within the touch screen at the location of the touch or proximity. A touch-sensor controller may process the change in capacitance to determine its position on the touch screen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example touch sensor with an example controller. 
         FIG. 2  illustrates a profile view of a portion of an example touch screen in which a pixel layer provides a pixel-drive signal to a display layer of a LCD, and a reference voltage layer provides the display layer of the LCD with a reference voltage and provides an integrated touch sensor with a drive signal. 
         FIG. 3  illustrates a profile view of a portion of an example touch screen in which a pixel-drive layer provides a pixel-drive signal to a display layer of a LCD and a drive signal to an integrated touch sensor, and a reference voltage layer provides a reference voltage for the display layer of the LCD and provides a sense signal to a touch screen controller. 
         FIG. 4  illustrates an overhead view of an example touch screen in which pixel-drive electrodes provide a display portion of a touch screen with a pixel-drive signal and provide an integrated touch sensor of the touch screen with a drive signal. 
         FIG. 5  illustrates an overhead view of an example touch screen in which a reference voltage layer provides a display portion of a touch screen with a reference voltage and provides an integrated touch sensor of the touch screen with a drive signal. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
       FIG. 1  illustrates an example touch sensor  10  with an example touch-sensor controller  12 . Touch sensor  10  and touch-sensor controller  12  may detect the presence and location of a touch or the proximity of an object within a touch-sensitive area of touch sensor  10 . Herein, reference to a touch sensor may encompass both the touch sensor and its touch-sensor controller, where appropriate. Similarly, reference, to a touch-sensor controller may encompass both the touch-sensor controller and its touch sensor, where appropriate. Touch sensor  10  may include one or more touch-sensitive areas, where appropriate. Touch sensor  10  may include an array of drive and sense electrodes (or an array of electrodes of a single type) disposed on one or more substrates, which may be made of a dielectric material and/or may be included in a display stack. Herein, reference to a touch sensor may encompass both the electrodes of the touch sensor and the substrate(s) that they are disposed on, where appropriate. Alternatively, where appropriate, reference to a touch sensor may encompass the electrodes of the touch sensor, but not the substrate(s) that they are disposed on. 
     An electrode (whether a drive electrode or a sense electrode) may be an area of conductive material forming a shape, such as for example a disc, square, rectangle, thin line, other suitable shape, or suitable combination of these. One or more cuts in one or more layers of conductive material may (at least in part) create the shape of an electrode, and the area of the shape may (at least in part) be bounded by those cuts. In particular embodiments, the conductive material of an electrode may occupy approximately 100% of the area of its shape. As an example and not by way of limitation, an electrode may be made of indium tin oxide (ITO) and the ITO of the electrode may occupy approximately 100% of the area of its shape (sometimes referred to as 100% fill), where appropriate. In particular embodiments, the conductive material of an electrode may occupy substantially less than 100% of the area of its shape. As an example and not by way of limitation, an electrode may be made of fine lines of metal or other conductive material (FLM) such as for example copper, silver, or a copper- or silver-based material and the fine lines of conductive material may occupy approximately 5% of the area of its shape in a hatched, mesh, or other suitable pattern. Herein, reference to FLM encompasses such material, where appropriate. Although this disclosure describes or illustrates particular electrodes made of particular conductive material forming particular shapes with particular fills having particular patterns, this disclosure. contemplates any suitable electrodes made of any suitable conductive material forming any suitable shapes with any suitable fill percentages having any suitable patterns. 
     Where appropriate, the shapes of the electrodes (or other elements) of a touch sensor may constitute in whole or in part one or more macro-features of the touch sensor. One or more characteristics of the implementation of those shapes (such as, for example, the conductive materials, fills, or patterns within the shapes) may constitute in whole or in part one or more micro-features of the touch sensor. One or more macro-features of a touch sensor may determine one or more characteristics of its functionality, and one or more micro-features of the touch sensor may determine one or more optical features of the touch sensor, such as transmittance, refraction, or reflection. 
     A mechanical stack may contain the substrate (or multiple substrates) and the conductive material forming the drive or sense electrodes of touch sensor  10 . In certain embodiments, the conductive material used for the drive or sense electrodes may also be used for a portion of the display screen (e.g., the same conductive material may be used for the sense electrodes of a touch sensor and for the reference voltage layer of a display screen). In some embodiments, the mechanical stack may be within or comprise a portion of a display stack configured to generate images. As an example and not by way of limitation, the mechanical stack may include a first layer of optically clear adhesive (OCA) beneath a cover panel of a display stack. The cover panel may be clear and made of a resilient material suitable for repeated touching, such as for example glass, polycarbonate, or poly(methyl methacrylate) (PMMA). This disclosure contemplates any suitable cover panel made of any suitable material. The first layer of OCA may be disposed between a layer or substrate of the display stack and the substrate with the conductive material forming the drive or sense electrodes. The substrate with the conductive material may provide a benefit or feature in producing an image (e.g., it may be a layer or substrate found in a typical, non-touch, display stack) or it may be a layer added specifically to provide a substrate on which the electrodes are formed. In some embodiments, the mechanical stack may also include a second layer of OCA. In some embodiments, the mechanical stack may also include a dielectric layer (which may be made of polyethylene terephthalate (PET) or another suitable material, similar to the substrate with the conductive material forming the drive or sense electrodes). As an alternative, where appropriate, a thin coating of a dielectric material may be applied instead of the second layer of OCA and/or the dielectric layer. The second layer of OCA may be disposed between the substrate with the conductive material making up the drive or sense electrodes and the dielectric layer, and the dielectric layer may be disposed between the second layer of OCA and another layer of the display stack. As an example only and not by way of limitation, the cover panel may have a thickness of approximately 1 mm; the first layer of OCA may have a thickness of approximately 0.05 mm; the substrate with the conductive material forming the drive or sense electrodes may have a thickness of approximately 0.05 mm; the second layer of OCA may have a thickness of approximately 0.05 mm; and the dielectric layer may have a thickness of approximately 0.05 mm. Although this disclosure describes a particular mechanical stack with a particular number of particular layers made of particular materials and having particular thicknesses, this disclosure contemplates any suitable mechanical stack with any suitable number of any suitable layers made of any writable materials and having any suitable thicknesses. 
     In particular embodiments, the drive or sense electrodes in touch sensor  10  may be made of ITO in whole or in part. In particular embodiments, the drive or sense electrodes in touch sensor  10  may be made of fine lines of metal or other conductive material. As an example and not by way of limitation, one or more portions of the conductive material may be copper or copper-based and have a thickness of approximately 5 μm or less and a width of approximately 10 μm or less. As another example, one or more portions of the conductive material may be silver or silver-based and similarly have a thickness of approximately 5 μm or less and a width of approximately 10 μm or less. This disclosure contemplates any suitable electrodes made of any suitable material. 
     Touch sensor  10  may implement a capacitive form of touch sensing. In a trautual-capacitance implementation, touch sensor  10  may include an array of drive and sense electrodes forming an array of capacitive nodes. A drive electrode and a sense electrode may form a capacitive node. The drive and sense electrodes forming the capacitive node may come near each other, but not make electrical contact with each other. Instead, the drive and sense electrodes may be capacitively coupled to each other across a space between them. A pulsed or alternating voltage applied to the drive electrode (by touch-sensor controller  12 ) may induce a charge on the sense electrode, and the amount of charge induced may be susceptible to external influence (such as a touch or the proximity of an object). When an object touches or comes within proximity of the capacitive node, a change in capacitance may occur at the capacitive node and touch-sensor controller  12  may measure the change in capacitance. By measuring changes in capacitance throughout the array, touch-sensor controller  12  may determine the position of the touch or proximity within the touch-sensitive area(s) of touch sensor  10 . 
     In a self-capacitance implementation, touch sensor  10  may include an array of electrodes of a single type that may each form a capacitive node. When an object touches or comes within proximity of the capacitive node, a change in self-capacitance may occur at the capacitive node and touch-sensor controller  12  may measure the change in capacitance, for example, as a change in the amount of charge needed to raise the voltage at the capacitive node by a pre-determined amount. As with a mutual-capacitance implementation, by measuring changes in capacitance throughout the array, touch-sensor controller  12  may determine the position of the touch or proximity within the touch-sensitive area(s) of touch sensor  10 . This disclosure contemplates any suitable form of capacitive touch sensing, where appropriate. 
     In particular embodiments, one or more drive electrodes may together form a drive line running horizontally or vertically or in any suitable orientation. Similarly, one or more sense electrodes may together form a sense line running horizontally or vertically or in any suitable orientation. In particular embodiments, drive lines may run substantially perpendicular to sense lines. Herein, reference to a drive line may encompass one or more drive electrodes making up the drive line, and vice versa, where appropriate. Similarly, reference to a sense line may encompass one or more sense electrodes making up the sense line, and vice versa, where appropriate. 
     Touch sensor  10  may have drive and sense electrodes disposed in a pattern on one side of a single substrate. In such a configuration, a pair of drive and sense electrodes capacitively coupled to each other across a space between them may form a capacitive node. For a self capacitance implementation, electrodes of only a single type may be disposed in a pattern on a single substrate, in addition or as an alternative to having drive and sense electrodes disposed in a pattern on one side of a single substrate, touch sensor  10  may have drive electrodes disposed in a pattern on one side of a substrate and sense electrodes disposed in a pattern on another side of the substrate. Moreover, touch sensor  10  may have drive electrodes disposed in a pattern on one side of one substrate and sense electrodes disposed in a pattern on one side of another substrate. In such configurations, an intersection of a drive electrode and a sense electrode may form a capacitive node. Such an intersection may be a location where the drive electrode and the sense electrode “cross” or come nearest each other in their respective planes. The drive and sense electrodes do not make electrical contact with each other—instead they are capacitively coupled to each other across a dielectric at the intersection. Although this disclosure describes particular configurations of particular electrodes forming particular nodes, this disclosure contemplates any suitable configuration of any suitable electrodes forming any suitable nodes. Moreover, this disclosure contemplates any suitable electrodes disposed on any suitable number of any suitable substrates in any suitable patterns. 
     As described above, a change in capacitance at a capacitive node of touch sensor  10  may indicate a touch or proximity input at the position of the capacitive node. Touch-sensor controller  12  may detect and process the change in capacitance to determine the presence and location of the touch or proximity input. Touch-sensor controller  12  may then communicate information about the touch or proximity input to one or more other components (such one or more central processing units (CPUs)) of a device that includes touch sensor  10  and touch-sensor controller  12 , which may respond to the touch or proximity input by initiating a function of the device (or an application running on the device) associated with it. Although this disclosure describes a particular touch-sensor controller having particular functionality with respect to a particular device and a particular touch sensor, this disclosure contemplates any suitable touch-sensor controller having any suitable functionality with respect to any suitable device and any suitable touch sensor. 
     Touch-sensor controller  12  may be one or more integrated circuits (ICs), such as for example general-purpose microprocessors, microcontrollers, programmable logic devices or arrays, or application-specific ICs (ASICs). In particular embodiments, touch-sensor controller  12  comprises analog circuitry, digital logic, and digital non-volatile memory. In particular embodiments, touch-sensor controller  12  is disposed on a flexible printed circuit (FPC) bonded to the substrate of touch sensor  10 . The FPC may be active or passive, where appropriate. In particular embodiments, multiple touch-sensor controllers  12  are disposed on the FPC. Touch-sensor controller  12  may include a processor unit, a drive unit, a sense unit, a display unit, and a storage unit. The drive unit may supply drive signals to the drive electrodes of touch sensor  10 . The sense unit may sense charge at the capacitive nodes of touch sensor  10  and provide measurement signals to the processor unit representing capacitances at the capacitive nodes, The processor unit may control the supply of drive signals to the drive electrodes by the drive unit and process measurement signals from the sense unit to detect and process the presence and location of a touch or proximity input within the touch-sensitive area(s) of touch sensor  10 . The processor unit may also track changes in the position of a touch or proximity input within the touch-sensitive area(s) of touch sensor  10 . The storage unit may store programming for execution by the processor unit, including programming for controlling the drive unit to supply drive signals to the drive electrodes, programming for processing measurement signals from the sense unit, and other suitable programming, where appropriate. Although this disclosure describes a particular touch-sensor controller having a particular implementation with particular components, this disclosure contemplates any suitable touch-sensor controller having any suitable implementation with any suitable components. 
     Tracks  14  of conductive material disposed on the substrate of touch sensor  10  may couple the drive or sense electrodes of touch sensor  10  to connection pads  16 , also disposed on the substrate of touch sensor  10 . As described below, connection pads  16  facilitate coupling of tracks  14  to touch-sensor controller  12 . Tracks  14  may extend into or around (e.g. at the edges of) the touch-sensitive area(s) of touch sensor  10 . Particular tracks  14  may provide drive connections for coupling touch-sensor controller  12  to drive electrodes of touch sensor  10 , through which the drive unit of touch-sensor controller  12  may supply drive signals to the drive electrodes. Other tracks  14  may provide sense connections for coupling touch-sensor controller  12  to sense electrodes of touch sensor  10 , through which the sense unit of touch-sensor controller  12  may sense charge at the capacitive nodes of touch sensor  10 . Tracks  14  may be made of fine lines of metal or other conductive material. As an example and not by way of limitation, the conductive material of tracks  14  may be copper or copper-based and have a width of approximately 100 μm or less. As another example, the conductive material of tracks  14  may be silver or silver-based and have a width of approximately 100 μm or less. In particular embodiments, tracks  14  may be made of ITO in whole or in part in addition or as an alternative to fine lines of metal or other conductive material. Although this disclosure describes particular tracks made of particular materials with particular widths, this disclosure contemplates any suitable tracks made of any suitable materials with any suitable widths. In addition to tracks  14 , touch sensor  10  may include one or more ground lines terminating at a ground connector (which may be a connection pad  16 ) at an edge of the substrate of touch sensor  10  (similar to tracks  14 ). 
     Connection pads  16  may be located along one or more edges of the substrate, outside the touch-sensitive area(s) of touch sensor  10 . As described above, touch-sensor controller  12  may be on an FPC. Connection pads  16  may be made of the same material as tracks  14  and may be bonded to the FPC using an anisotropic conductive film (ACF). Connection  18  may include conductive lines on the FPC coupling touch-sensor controller  12  to connection pads  16 , in turn coupling touch-sensor controller  12  to tracks  14  and to the drive or sense electrodes of touch sensor  10 . This disclosure contemplates any suitable connection  18  between touch-sensor controller  12  and touch sensor  10 . 
       FIG. 2  illustrates a profile view of a portion of an example touch screen in which a pixel layer provides a pixel-drive signal to a display layer of a LCD, and a reference voltage layer provides the display layer of the LCD with a reference voltage and provides an integrated touch sensor with a drive signal. Touch screen  200  includes a stack of layers that provide both an image, via a display portion, and touch sensing, via an integrated touch sensor. The display portion of touch screen  200  is configured to provide images through a two-dimensional array of pixels. The touch sensor is configured to determine a relative location of a touch input within touch screen  200 . The depicted layers of touch screen  200  are display layer(s)  210 , reference voltage layer  220 , sensor substrate  230 , sense electrodes  240 , and pixel layer  250 . Additional layers of touch screen  200  are not depicted. For example, touch screen  300  may include one or more layers, materials, and/or components above sense electrodes  240 , below pixel layer  250 , and/or in-between any of the other depicted layers of touch screen  200 . 
     Display layer(s)  210  may include pixels which provide images for touch screen  200 . Display layer(s)  210  may include any suitable number of layers of touch screen  200 . For example, display layer(s)  210  may include a single display layer or more than one display layer. In some embodiments, display layer(s)  210  may be a liquid crystal layer that adjusts a polarization of light passing through the layer. In some embodiments, display layer(s)  210  may be the liquid crystal layer and any combination of one or more glass substrate layers with electrodes and or one or more polarizing filter layers. In some embodiments, display layer(s)  210  may include VCOM layer(s) and/or pixel layer(s). 
     The color of the pixels of display layer(s)  210  may be determined, in part, based on an electrical potential between a pixel layer  250  and reference voltage layer  220  The reference voltage may be referred to as a common voltage or VCOM. In addition to providing a reference voltage for display layer(s)  210 , reference voltage layer  220  may also provide the drive signal for a touch sensor. For example, in the embodiment depicted in  FIG. 2 , the touch sensor portion of touch screen  200  may include sense electrodes  240 , sensor substrate  230 , and reference voltage layer  220 . In such an embodiment, reference voltage layer  220  may act as the drive electrodes of a touch sensor. This may allow the same layer, reference voltage layer  220 , to provide both a reference voltage for display layer(s)  210  and a drive signal for a touch sensor. 
     Reference voltage layer  220  may he electrically conductive so as to provide both the reference voltage and the drive signal. In certain embodiments, the reference voltage layer  220  may comprise ITO. In some embodiments, reference voltage layer  220  may include fine lines of metal. The fine lines of metal may be used to provide both the reference voltage for display layer(s)  210  as well as the drive signals for the touch sensor. In some embodiments, the fine lines of metal may be arranged in a mesh configuration. In some embodiments, the fine lines of metal, may be electrically isolated drive lines that are all pulsed simultaneously to provide the reference voltage for display layer(s)  210 . In some embodiments, the fine lines of metal may be electrically isolated drive lines that are each pulsed one at a time to provide drive signals to sense electrodes  240 . In some embodiments, instead of pulsing each of the electrically isolated drive lines one at a time to provide drive signals to sense electrodes  240 , two or more of the electrically isolated drive lines (such as, for example, two of the electrically isolated drive lines, three of the electrically isolated drive lines, or any other number of the electrically isolated drive lines) may be pulsed simultaneously to provide drive signals to sense electrodes  240 . 
     In the depicted embodiment, sensor substrate  230  is located between sense electrodes  240  and reference voltage layer  220 . In some embodiments, sensor substrate  230  may comprise an additional layer that would not be fund in a traditional non-touch sensitive LCD display stack. In some such embodiments, sensor substrate  230  may comprise non-birefringent material. The use of a non-birefringent material may avoid undesirable twisting of the light passing through the material. In some embodiments, sensor substrate  230  may comprise an existing layer that would be found in a traditional non-touch sensitive LCD display stack. For example, sensor substrate  230  may be a color filter layer of an LCD display stack. In some embodiments, sensor substrate  230  may comprise multiple layers, 
     Pixel layer  250  may be configured to change the characteristics of the crystals within display layer(s)  210  (e.g., to change the image to be displayed by touch screen  200 ), In particular embodiments, pixel layer  250  may comprise a two-dimensional array of pixel electrodes. The size of the two-dimensional array of pixel electrodes may correspond to the number of display pixels of touch screen  200  (e.g., each pixel to be displayed may have its own respective pixel electrode(s)). In some embodiments, each pixel electrode may he individually controlled to generate an image. 
     Although the depicted embodiment includes an LCD display stack, other embodiments may comprise other types of display stacks (e.g., any display stack that includes a reference voltage layer). For example, in some embodiments, an organic light emitting diode (OLED) display stack may be used for touch screen  200 . 
       FIG. 3  illustrates a profile view of a portion of an example touch screen in which a pixel-drive layer provides a pixel-drive signal to a display layer of a LCD and a drive signal to an integrated touch sensor, and a reference voltage layer provides a reference voltage for the display layer of the LCD and provides a sense signal to a touch screen controller. Similar to touch screen  200 , touch screen  300  provides both an image and touch sensitivity. In  FIG. 3 , touch screen  300  may include several layers. The depicted layers of touch screen  300  include voltage layer  340 , display layer(s)  310 , and pixel-drive layer  330 . Additional layers of touch screen  300  are not depicted. For example, touch screen  300  may include one or more layers, materials, and/or components above voltage layer  340 , below pixel-drive layer  330 , and/or in-between any of the other depicted layers of touch screen  300 . 
     In the embodiment depicted in  FIG. 3 , the drive and sense electrodes of a touch sensor are implemented through pixel-drive layer  330  and reference voltage layer  340 , respectively. These layers also provide their traditional functionality for display layer(s)  310 . 
     For example, pixel-drive layer  330  may be configured to change the characteristics of the crystals within display layer(s)  310  (e.g., to change the image to be displayed by touch screen  300 ) and may be configured to provide a drive signal for a touch sensor; and reference voltage layer  340  may be configured to provide a reference voltage for display layer(s)  310  and may be configured to provide sense signals to a touch screen controller (i.e., where the sense signals are provided by the reference voltage layer  340  as a result of the drive signals provided to the reference voltage layer  340  by pixel-drive layer  330 ). In addition, in the depicted embodiment, display layer(s)  310  may also act as the sensor substrate for the touch sensor. 
     In particular embodiments, pixel-drive layer  330  may comprise a two-dimensional array of pixel-drive electrodes, The size of the two-dimensional array of pixel-drive electrodes may correspond to the number of display pixels of touch screen  300  (e.g., each pixel to be displayed may have its own respective pixel-drive electrode). While the pixel-drive electrodes may be individually controlled to generate an image, in some embodiments they may be grouped together to provide drive signals for the touch sensor. For example, one or more rows of pixel-drive electrodes may be used collectively as a single drive electrode (e.g., the same drive signal may be sent to all the pixel-drive electrodes within one or more rows pixel drive electrodes). 
     In some embodiments, one or both of pixel-drive layer  330  and reference voltage layer  340  may comprise fine lines of metal, in particular embodiments, the fine lines of metal for pixel-drive layer  330  and/or reference voltage layer  340  may be arranged in a mesh fashion. In some embodiments, fine lines of metal may be connected between the pixel-drive electrodes and a touch screen controller. Although the depicted embodiment includes an LCD display stack, other embodiments may comprise other types of display stacks (e.g., any display stack that includes a reference voltage layer). For example, in some embodiments, an organic light emitting diode (OLED) display stack may be used for touch screen  300 . 
       FIG. 4  illustrates an overhead view of an example touch screen in which pixel-drive electrodes provide a display portion of a touch screen with a pixel-drive signal and provide an integrated touch sensor of the touch screen with a drive signal. In the depicted embodiment, touch screen  400  comprises a four-by-four display with an integrated two-by-two touch sensor, The four-by-four display comprises the individual pixels of display layer(s) (not depicted). Each pixel of the display has its own associated pixel-drive electrode  430 . These pixel-drive electrodes  430  are grouped into subsets of pixel-drive electrodes  430  to form drive electrodes  480 . The two-by-two touch sensor comprises sense electrodes  440  and the two subsets of pixel-drive electrodes  430  that form drive electrodes  480 . In order to form drive electrodes  480 , pixel-drive electrodes  430  are arranged into two subsets (drive electrode  480   a  and drive electrode  480   b ), each subset comprises a two-by-four array of pixel-drive electrodes  430 . Controller  450  is separately connected to each pixel-drive electrode  430  and thus may treat pixel-drive electrodes  430  as separate entities when generating an image and collectively (as subsets) when generating a drive signal to determine a location of a touch input. In this embodiment, the sensor substrate (not shown), is located between sense electrodes  440  and drive electrodes  480 . 
     In the depicted embodiment, touch screen controller  450  is connected to sense electrodes  440  as well as the individual pixel drive electrodes  430  that form drive electrodes  480 . This may allow touch screen controller  450  to both adjust the pixel-drive signal to control the image generated by touch screen  400  and to manage the drive signal for the touch sensor used to determine the relative location of a touch input. Because pixel-drive electrodes  430  are used for both the touch sensor functionality and for creating the displayed image, touch screen controller  450  may need to synchronize how and when it sends pixel-drive signals and drive signals. 
     While the pixel-drive electrodes have been grouped together in rows in the depicted embodiment, some embodiments may group the pixel-drive electrodes into clusters (e.g., two-by-two clusters) or may not group them together at all. For example, sense electrodes  440  may separately detect a touch input based on a change in the charge, capacitance, or electrical potential from each of the individual pixel-drive electrodes. 
       FIG. 5  illustrates an overhead view of an example touch screen in which a reference voltage layer provides a display portion of a touch screen with a reference voltage and provides an integrated touch sensor of the touch screen with a drive signal. In  FIG. 5 , touch screen  500  includes touch screen controller  550  coupled to drive electrodes  530  and sense electrodes  540 . Drive electrodes  530  may he spaced so as to provide a reference voltage for a display layer(s) (not depicted). Drive electrodes  530  may also be configured to provide drive signals to a touch sensor, In some embodiments, drive electrodes  530  may be oriented perpendicularly to the orientation of sense electrodes  540 . In some embodiments, drive electrodes  530  may be made of fine lines of metal. Touch screen controller  550  may use drive electrodes  530  to provide drive signals for a touch sensor and to provide a reference voltage for a display layer(s) (e.g., display layer(s)  210  of an LCD display stack). As discussed above with respect to  FIG. 4 , touch screen controller  550  may synchronize the reference voltage and the drive signals being sent over drive electrodes  530 . Touch screen controller  550  may then use the sense signal provided by sense electrodes  540  to determine a relative location of a touch input. 
     Although  FIGS. 1-5  have been described above as including particular components, the systems of  FIGS. 1-5  may include any combination of any of the described components and any of the options or features described herein, as would be understood by one of ordinary skill in the art based upon the teachings of the disclosure. For example and not by way of limitation, any of the options or features described herein may be utilized in combination with the illustrated embodiments of  FIGS. 1-5  and/or any number of the other options or features also described herein as would be understood by one of ordinary skill in the art based upon the teachings of the disclosure. 
     Herein, reference to a computer-readable non-transitory storage medium may include a semiconductor-based or other integrated circuit (IC), such as for example a field-programmable gate array (FPGA) or an application-specific IC (ASIC), a hard disk, an HUD, a hybrid hard drive (HHD), an optical disc, an optical disc drive (ODD), a magneto-optical disc, a magneto-optical drive, a floppy disk, a floppy disk drive (FDD), magnetic tape, a holographic storage medium, a solid-state drive (SSD), a RAM-drive, a SECURE DIGITAL card, a SECURE DIGITAL drive, another suitable medium, or a suitable combination of these, where appropriate, A computer-readable non-transitory storage medium may be volatile, non-volatile, or a combination of volatile and non-volatile, where appropriate. 
     Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context. 
     This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person haying ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative.