Patent Publication Number: US-8976133-B2

Title: Devices and methods for improving image quality in a display having multiple VCOMs

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Non-Provisional patent application of U.S. Provisional Patent Application No. 61/657,667, entitled “Devices and Methods for Improving Image Quality in a Display Having Multiple VCOMs”, filed Jun. 8, 2012, which are herein incorporated by reference. 
    
    
     BACKGROUND 
     The present disclosure relates generally to electronic displays and, more particularly, to improving the image quality in a display having multiple common voltage layers (VCOMs). 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Electronic displays, such as liquid crystal displays (LCDs), are commonly used in electronic devices such as televisions, computers, and phones. The electronic displays may portray images by modulating the amount of light that passes through a liquid crystal layer within pixels of varying color. For example, by varying a voltage difference between a pixel electrode and a common electrode in a pixel, an electric field may result. The electric field may cause the liquid crystal layer to vary its alignment, which may ultimately result in more or less light being emitted through the pixel where it may be seen. By changing the voltage difference (often referred to as a data signal) supplied to each pixel, images may be produced on the display. To store data representing a particular amount of light that is to be passed through pixels, gates of thin-film transistors (TFTs) in the pixels may be activated while the data signal is supplied to the pixels. 
     Electronic displays may include a touch screen for receiving inputs from an operator of the electronic device in which the electronic display is incorporated. In certain configurations, the display may include segmented VCOMs such that a portion of the pixels of the display use a first VCOM and a portion of the pixels of the display use a second VCOM. While operating a touch screen of a display that includes segmented VCOMs, the image quality of the display may be adversely affected because of the segmented VCOMs. For example, pixels using the first VCOM may display an image differently than pixels using the second VCOM. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     Embodiments of the present disclosure relate to devices and methods for improving image quality in a display having multiple common voltage layers (VCOMs). By way of example, a method for improving image quality in a display having multiple VCOMs may include maintaining a deactivation signal on pixels of the display after programming a frame of data onto the pixels of the display, but before a touch sequence. The method may also include supplying a first data signal to each pixel of a first set of pixels coupled to a first VCOM while maintaining the deactivation signal. The method may include supplying a second data signal to each pixel of a second set of pixels coupled to a second VCOM while supplying the first data signal. The first data signal is supplied to each pixel of the first set of pixels and the second data signal is supplied to each pixel of the second set of pixels to inhibit image distortion during the touch sequence. 
     Various refinements of the features noted above may be made in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a schematic block diagram of an electronic device with a display that may have multiple common voltage layers (VCOMs), in accordance with an embodiment; 
         FIG. 2  is a perspective view of a notebook computer representing an embodiment of the electronic device of  FIG. 1 ; 
         FIG. 3  is a front view of a handheld device representing another embodiment of the electronic device of  FIG. 1 ; 
         FIG. 4  is a circuit diagram illustrating display circuitry used to improve image quality of a display having multiple VCOMs, in accordance with an embodiment; 
         FIG. 5  is a circuit diagram illustrating circuitry of an electronic device for applying different signals to different VCOMs of a display having multiple VCOMs to improve image quality of the display, in accordance with an embodiment; 
         FIG. 6  is a diagram illustrating a relationship between a gate-to-source voltage of a TFT and a drain-to-source current of the TFT, in accordance with an embodiment; and 
         FIG. 7  is a flowchart describing a method for improving image quality in a display having multiple VCOMs, in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     As mentioned above, embodiments of the present disclosure relate to displays and electronic devices incorporating displays that employ a device, method, or combination thereof for improving image quality in a display having multiple common voltage layers (VCOMs). Specifically, rather than supplying a uniform data signal (e.g., the same voltage, an open circuit, ground) to all pixels of a display while the display is being operated in a touch mode (e.g., a time when the pixels are not activated for storing data on the pixels), which could result in undesirable image quality (e.g., color variations between different portions of the display), embodiments of the present disclosure may incorporate hardware, software, or a combination thereof for supplying different data signals (e.g., different voltages) to pixels located on different VCOMs while the display is being operated in the touch mode to improve image quality. 
     Specifically, to improve image quality of the display during a touch mode, the display may generally operate in a standard manner during a display mode. At the end of the display mode or the beginning of a touch mode, a first data signal may be supplied to a first set of pixels coupled to a first VCOM and a second data signal may be supplied to a second set of pixels coupled to a second VCOM. The first and second data signals are supplied to the source lines of the pixels while the gate lines of the pixels remain deactivated. Accordingly, separate voltages are applied to the source lines of separate VCOMs. These first and second data signals may be applied before the touch mode, through a portion of the touch mode, and/or throughout the touch mode. As a result, it is believed that the leakage current of the TFTs (e.g., of pixels) may be reduced and, accordingly, image quality between portions of the display using different VCOMs may be improved. 
     With the foregoing in mind, a general description of suitable electronic devices that may employ electronic displays having capabilities to control supplying different data signals to pixels on different VCOMs is described below. In particular,  FIG. 1  is a block diagram depicting various components that may be present in an electronic device suitable for use with such a display.  FIGS. 2 and 3  respectively illustrate perspective and front views of a suitable electronic device, which may be, as illustrated, a notebook computer or a handheld electronic device. 
     Turning first to  FIG. 1 , an electronic device  10  according to an embodiment of the present disclosure may include, among other things, one or more processor(s)  12 , memory  14 , nonvolatile storage  16 , a display  18 , input structures  22 , an input/output (I/O) interface  24 , network interfaces  26 , and a power source  28 . The various functional blocks shown in  FIG. 1  may include hardware elements (including circuitry), software elements (including computer code stored on a computer-readable medium) or a combination of both hardware and software elements. It should be noted that  FIG. 1  is merely one example of a particular implementation and is intended to illustrate the types of components that may be present in the electronic device  10 . As may be appreciated, when the leakage current of TFTs varies between different VCOMs of the display  18 , image quality of the display  18  may be distorted if the source of each TFTs are held the same way. For example, portions of the display  18  using one VCOM may produce different colors than portions of the display  18  using a different VCOM. As such, embodiments of the present disclosure may be employed to increase image quality. 
     By way of example, the electronic device  10  may represent a block diagram of the notebook computer depicted in  FIG. 2 , the handheld device depicted in  FIG. 3 , or similar devices. It should be noted that the processor(s)  12  and/or other data processing circuitry may be generally referred to herein as “data processing circuitry.” This data processing circuitry may be embodied wholly or in part as software, firmware, hardware, or any combination thereof. Furthermore, the data processing circuitry may be a single contained processing module or may be incorporated wholly or partially within any of the other elements within the electronic device  10 . As presented herein, the data processing circuitry may control the source lines of the TFTs of the electronic display  18  to alter the voltage applied to the sources of the TFTs and thereby alter the leakage current of TFTs among the different VCOMs of the display  18 . 
     In the electronic device  10  of  FIG. 1 , the processor(s)  12  and/or other data processing circuitry may be operably coupled with the memory  14  and the nonvolatile memory  16  to execute instructions. Such programs or instructions executed by the processor(s)  12  may be stored in any suitable article of manufacture that includes one or more tangible, computer-readable media at least collectively storing the instructions or routines, such as the memory  14  and the nonvolatile storage  16 . The memory  14  and the nonvolatile storage  16  may include any suitable articles of manufacture for storing data and executable instructions, such as random-access memory, read-only memory, rewritable flash memory, hard drives, and optical discs. Also, programs (e.g., an operating system) encoded on such a computer program product may also include instructions that may be executed by the processor(s)  12 . 
     The display  18  may be a touch-screen liquid crystal display (LCD), for example, which may enable users to interact with a user interface of the electronic device  10 . In some embodiments, the electronic display  18  may be a MultiTouch™ display that can detect multiple touches at once. As may be described further below, the electronic device  10  may include circuitry to control the source lines of the TFTs of the display  18 . 
     The input structures  22  of the electronic device  10  may enable a user to interact with the electronic device  10  (e.g., pressing a button to increase or decrease a volume level). The I/O interface  24  may enable electronic device  10  to interface with various other electronic devices, as may the network interfaces  26 . The network interfaces  26  may include, for example, interfaces for a personal area network (PAN), such as a Bluetooth network, for a local area network (LAN), such as an 802.11x Wi-Fi network, and/or for a wide area network (WAN), such as a 3G or 4G cellular network. The power source  28  of the electronic device  10  may be any suitable source of power, such as a rechargeable lithium polymer (Li-poly) battery and/or an alternating current (AC) power converter. 
     The electronic device  10  may take the form of a computer or other type of electronic device. Such computers may include computers that are generally portable (such as laptop, notebook, and tablet computers) as well as computers that are generally used in one place (such as conventional desktop computers, workstations and/or servers). In certain embodiments, the electronic device  10  in the form of a computer may be a model of a MacBook®, MacBook® Pro, MacBook Air®, iMac®, Mac® mini, or Mac Pro® available from Apple Inc. By way of example, the electronic device  10 , taking the form of a notebook computer  30 , is illustrated in  FIG. 2  in accordance with one embodiment of the present disclosure. The depicted computer  30  may include a housing  32 , a display  18 , input structures  22 , and ports of an I/O interface  24 . In one embodiment, the input structures  22  (such as a keyboard and/or touchpad) may be used to interact with the computer  30 , such as to start, control, or operate a GUI or applications running on computer  30 . For example, a keyboard and/or touchpad may allow a user to navigate a user interface or application interface displayed on the display  18 . Further, the display  18  may include TFTs that are controlled to improve image quality of the display  18 . 
       FIG. 3  depicts a front view of a handheld device  34 , which represents one embodiment of the electronic device  10 . The handheld device  34  may represent, for example, a portable phone, a media player, a personal data organizer, a handheld game platform, or any combination of such devices. By way of example, the handheld device  34  may be a model of an iPod® or iPhone® available from Apple Inc. of Cupertino, Calif. In other embodiments, the handheld device  34  may be a tablet-sized embodiment of the electronic device  10 , which may be, for example, a model of an iPad® available from Apple Inc. 
     The handheld device  34  may include an enclosure  36  to protect interior components from physical damage and to shield them from electromagnetic interference. The enclosure  36  may surround the display  18 , which may display indicator icons  38 . The indicator icons  38  may indicate, among other things, a cellular signal strength, Bluetooth connection, and/or battery life. The I/O interfaces  24  may open through the enclosure  36  and may include, for example, a proprietary I/O port from Apple Inc. to connect to external devices. 
     User input structures  40 ,  42 ,  44 , and  46 , in combination with the display  18 , may allow a user to control the handheld device  34 . For example, the input structure  40  may activate or deactivate the handheld device  34 , the input structure  42  may navigate a user interface to a home screen, a user-configurable application screen, and/or activate a voice-recognition feature of the handheld device  34 , the input structures  44  may provide volume control, and the input structure  46  may toggle between vibrate and ring modes. A microphone  48  may obtain a user&#39;s voice for various voice-related features, and a speaker  50  may enable audio playback and/or certain phone capabilities. A headphone input  52  may provide a connection to external speakers and/or headphones. As mentioned above, the display  18  may include TFTs that are controlled to vary leakage current among the different VCOMs of the display  18 . 
     Among the various components of an electronic display  18  may be a pixel array  100 , as shown in  FIG. 4 . As illustrated,  FIG. 4  generally represents a circuit diagram of certain components of the display  18  in accordance with an embodiment. In particular, the pixel array  100  of the display  18  may include a number of unit pixels  102  disposed in a pixel array or matrix. In such an array, each unit pixel  102  may be defined by the intersection of rows and columns, represented by gate lines  104  (also referred to as scanning lines), and source lines  106  (also referred to as data lines), respectively. Although only six unit pixels  102 , referred to individually by the reference numbers  102 A- 102 F, respectively, are shown for purposes of simplicity, it should be understood that in an actual implementation, each source line  106  and gate line  104  may include hundreds or thousands of such unit pixels  102 . Each of the unit pixels  102  may represent one of three subpixels that respectively filters only one color (e.g., red, blue, or green) of light. For purposes of the present disclosure, the terms “pixel,” “subpixel,” and “unit pixel” may be used largely interchangeably. 
     In the presently illustrated embodiment, each unit pixel  102  includes a thin film transistor (TFT)  108  for switching a data signal supplied to a respective pixel electrode  110 . The potential stored on the pixel electrode  110  relative to a potential of a common electrode  112 , which may be shared by other pixels  102 , may generate an electrical field sufficient to alter the arrangement of a liquid crystal layer of the display  18 . In the depicted embodiment of  FIG. 4 , a source  114  of each TFT  108  may be electrically connected to a source line  106  and a gate  116  of each TFT  108  may be electrically connected to a gate line  104 . A drain  118  of each TFT  108  may be electrically connected to a respective pixel electrode  110 . Each TFT  108  may serve as a switching element that may be activated and deactivated (e.g., turned on and off) for a period of time based on the respective presence or absence of a scanning or activation signal on the gate lines  104  that are applied to the gates  116  of the TFTs  108 . 
     When activated, a TFT  108  may store the image signals received via the respective source line  106  as a charge upon its corresponding pixel electrode  110 . As noted above, the image signals stored by the pixel electrode  110  may be used to generate an electrical field between the respective pixel electrode  110  and a common electrode  112 . This electrical field may align the liquid crystal molecules within the liquid crystal layer to modulate light transmission through the pixel  102 . Thus, as the electrical field changes, the amount of light passing through the pixel  102  may increase or decrease. In general, light may pass through the unit pixel  102  at an intensity corresponding to the applied voltage from the source line  106 . 
     The display  18  also may include a source driver integrated circuit (IC)  120 , which may include a processor, microcontroller, or application specific integrated circuit (ASIC), that controls the display pixel array  100  by receiving image data  122  from the processor(s)  12  and sending corresponding image signals to the unit pixels  102  of the pixel array  100 . It should be understood that the source driver  120  may be a chip-on-glass (COG) component on a TFT glass substrate, a component of a display flexible printed circuit (FPC), and/or a component of a printed circuit board (PCB) that is connected to the TFT glass substrate via the display FPC. Further, the source driver  120  may include any suitable article of manufacture having one or more tangible, computer-readable media for storing instructions that may be executed by the source driver  120 . 
     The source driver  120  also may couple to a gate driver integrated circuit (IC)  124  that may activate or deactivate rows of unit pixels  102  via the gate lines  104 . As such, the source driver  120  may provide timing signals  126  to the gate driver  124  to facilitate the activation/deactivation of individual rows (i.e., lines) of pixels  102 . In other embodiments, timing information may be provided to the gate driver  124  in some other manner. The display  18  may include a Vcom source  128  to provide a VCOM output to the common electrodes  112 . In some embodiments, the Vcom source  128  may supply a different VCOM to different common electrodes  112  at different times. In other embodiments, the common electrodes  112  all may be maintained at the same potential (e.g., a ground potential) while the display  18  is on. 
     There are many ways to configure the circuitry of the electronic device  10  so that source lines  106  may be used to vary the leakage current of the TFTs  108  based on which VCOM of the display  18  the pixels  102  are located.  FIG. 5  generally represents one embodiment of a circuit diagram of components of the electronic device  10  for applying different signals to different VCOMs of the display  18  having multiple VCOMs to improve image quality of the display  18 . In particular, the electronic device  10  includes a VCOM_A  130 , a VCOM_B  132 , a VCOM_C  134 , a VCOM_D  136 , a VCOM_E  138 , a VCOM_F  140 , and a VCOM_G  142 . As illustrated, the VCOM_A  130 , the VCOM_B  132 , the VCOM_C  134 , the VCOM_D  136 , the VCOM_E  138 , the VCOM_F  140 , and the VCOM_G  142  each have multiple pixels  102  coupled thereon. As may be appreciated, the VCOMs may have any number of pixels  102  coupled thereon. Furthermore, there may be any number of VCOMs of the display  18 . It should be noted that, the common electrodes  112  of the illustrated pixels  102  may be electrically coupled to their respective VCOM. 
     In certain embodiments, the VCOMs of the display  18  may be arranged into rows and columns. The rows and columns of the VCOMs may be used during a touch mode of the display for sensing touches of the display. For example, a touch driving signal (e.g., a low voltage AC signal) may be supplied to one or more rows of VCOMs. While the signal is supplied, a touch may be sensed using one or more columns of VCOMs. In the present embodiment, the VCOM_A  130  and the VCOM_E  138  may be part of a row of VCOMs. Accordingly, the VCOM_A  130  and the VCOM_E  138  may be electrically coupled together. Furthermore, the VCOM_A  130  and the VCOM_E  138  may be electrically coupled to a VCOM TX    144  configured to provide a touch driving signal to the row of VCOMs. As may be appreciated, the display  18  may include one or more VCOM TX    144  to drive the rows of VCOMs of the display  18 . 
     The VCOM_C  134  and the VCOM_G  142  may be part of the columns of VCOMs of the display  18 . For example, the VCOM_C  134  may be part of one column of VCOMs and the VCOM_G  142  may be part of another column of VCOMs. As illustrated, the VCOM_C  134  and the VCOM_G  142  may be electrically coupled together. Furthermore, the VCOM_C  134  and the VCOM_G  142  may be electrically coupled to a VCOM RX    146  configured to sense a touch of the display  18 . As may be appreciated, the display  18  may include one or more VCOM RX    146  to sense touches of the display  18 . For example, the display  18  may include one VCOM RX    146  for each column of VCOMs. 
     The display  18  may include VCOMs that function as guard rails configured to inhibit direct capacitive coupling (e.g., without a touch such as from a finger) from occurring between the rows and columns of VCOMs. As illustrated, the VCOM_B  132 , the VCOM_D  136 , and the VCOM_F  140  may all be guard rails. As illustrated, the VCOM_B  132 , the VCOM_D  136 , and the VCOM_F  140  may be electrically coupled together. Furthermore, the VCOM_B  132 , the VCOM_D  136 , and the VCOM_F  140  may be electrically coupled to a VCOM GR    148 . As may be appreciated, the display  18  may include one or more VCOM GR    148  that may provide signals to the guard rails. 
     The gate driver  124  is coupled to the gate lines  104  for activating and/or deactivating the gates  116  of the TFTs  108  of the pixels  102 . Furthermore, the source driver  120  is coupled to the source lines  106  for supplying data signals to the sources  114  of the TFTs  108  of the pixels  102 . As may be appreciated, the source driver  120  may supply data signals to pixels  102  based on the VCOM that the pixels  102  are coupled to. For example, the source driver  120  may supply data signals of a first voltage to pixels  102  of VCOM rows (e.g., SOURCE TX    150 ). Furthermore, the source driver  120  may supply data signals of a second voltage to pixels  102  of VCOM guard rails (e.g., SOURCE GR    152 ). Moreover, the source driver  120  may supply data signals of a third voltage to pixels  102  of VCOM columns (e.g., SOURCE RX    154 ). Although the SOURCE TX    150 , the SOURCE GR    152 , and the SOURCE RX    154  are illustrated as being part of the source driver  120 , it should be noted that the SOURCE TX    150 , the SOURCE GR    152 , and the SOURCE RX    154  are illustrated to show that different signals may be supplied to different VCOMs of the display  12  and not that there are necessarily such devices within the source driver  120 . 
     As illustrated, the VCOM_A  130 , the VCOM_B  132 , the VCOM_C  134 , the VCOM_D  136 , the VCOM_E  138 , the VCOM_F  140 , and the VCOM_G  142  may not physically be the same size. Accordingly, the VCOM_A  130 , the VCOM_B  132 , the VCOM_C  134 , the VCOM_D  136 , the VCOM_E  138 , the VCOM_F  140 , and the VCOM_G  142  may have resistive differences. In certain embodiments, the VCOM_A  130  and the VCOM_E  138  may be approximately the same size. Furthermore, the VCOM_C  134  and the VCOM_G  142  may be approximately the same size. Moreover, the VCOM_B  132 , the VCOM_D  136 , and the VCOM_F  140  may be approximately the same size. 
     During operation, the display  18  may alternate between a display mode and a touch mode. During the display mode, the display  18  receives image data and provides data signals to pixels  102  to store the image data on the pixels  102 . During the touch mode, the display  18  provides a touch driving signal and senses touches that occur. As may be appreciated, when the touch driving signal is applied to the display  18 , a gate-to-source voltage of the TFTs  108  of the pixels  102  may be modified, which may result in an increased leakage current (e.g., drain-to-source current) of the TFTs  108 .  FIG. 6  is a diagram  156  illustrating a relationship between a gate-to-source voltage  158  of a TFT  108  and a drain-to-source current  160  of the TFT  108 . 
     Specifically, the drain-to-source current  160  is negative during a segment  162 . At the end of segment  162 , the drain-to-source current  160  reaches zero, at point  164 . The gate-to-source voltage  158  at point  164  is indicated by a voltage  166  which is a negative voltage. During a segment  168 , the drain-to-source current  160  is positive. Accordingly, if the gate-to-source voltage  158  were to fluctuate about the axis  160  based on a touch driving signal (e.g., a low voltage AC signal), the drain-to-source current  160  would fluctuate between a low positive value and a high positive value, resulting in a potential for high leakage, which in turn may decrease the quality of the image of the display  18 . However, if the gate-to-source voltage  158  were to fluctuate about an axis formed by the voltage  166 , the drain-to-source current  160  would fluctuate between a low negative value and a low positive value, resulting in lower leakage and improving the quality of the image of the display  18 . Accordingly, voltages are applied to the source lines  106  to change the gate-to-source voltage  158  and thereby shift the axis related to the drain-to-source current  160  fluctuations. 
     In certain embodiments, voltages may be applied to the source lines  106  as part of the display mode and remain applied during the touch mode until the display mode resumes. Specifically, data may be stored on the pixels  102  of the display  18  line by line during the display mode until all lines of pixels  102  have data stored on them. For example, if the display  18  were to have 960 lines of pixels  102 , during the display mode all 960 lines of pixels  102  may have data stored on them. In certain embodiments, as part of the display mode, the display  18  may act as if it contains a 961st line of pixels  102  (e.g., a virtual line). For the 961st line of pixels  102 , voltages are applied to the source lines  106  just as when other lines of pixels  102  store data; however, the gate lines  104  are not activated (e.g., remain deactivated) so that data is not stored on the pixels  102 . Furthermore, the voltages applied to the source lines  106  remain after the display mode ends and through the touch mode until the display mode begins again. As such, the voltages applied to the source lines  106  may be considered “parked.” 
     As previously discussed, the voltages applied to the source lines  106  may vary based on the VCOMs that the source lines  106  provide signals to. The voltages may vary in order to tune each set of pixels  102  coupled to a single VCOM so that the TFTs  108  of the VCOM have a minimum amount of leakage current. The difference in voltage between different VCOMs may be due in part to the size of the VCOMs, the number of pixels  102  coupled to the VCOMs, and so forth. In one embodiment, the voltage applied to the source lines represented by SOURCE TX    150  may be approximately a grey 255 voltage, the voltage applied to the source lines represented by SOURCE GR    152  may be approximately a grey 127 voltage, and the voltage applied to the source lines represented by SOURCE RX    154  may be approximately a grey 0 voltage. In another embodiment, the voltage applied to the source lines represented by SOURCE TX    150  may be approximately a grey 255 voltage, the voltage applied to the source lines represented by SOURCE GR    152  may be approximately a grey 204 voltage, and the voltage applied to the source lines represented by SOURCE RX    154  may be approximately a grey 192 voltage. In other embodiments, the voltages applied to the source lines represented by SOURCE TX    150 , SOURCE GR    152 , and SOURCE RX    154  may be tuned to any suitable voltage. Accordingly, the leakage current of TFTs  108  of the pixels  102  may be reduced and the image quality of the display  18  may be improved. 
     The different voltages applied to the source lines  106  may be provided in any suitable manner.  FIG. 7  is a flowchart describing a method  170  that provides different voltages to the source lines  106  to improve image quality of a display  18  having multiple VCOMs. At block  172 , a first data signal is supplied to each pixel  102  of a first set of pixels  102  coupled to a first VCOM (e.g., VCOM_A  130 ). Then, at block  174 , a second data signal is supplied to each pixel  102  of a second set of pixels  102  coupled to a second VCOM (e.g., VCOM_C  134 ) while the first data signal is supplied. A third data signal is supplied to each pixel  102  of a third set of pixels  102  coupled to a third VCOM (e.g., VCOM_B  132 ) (block  176 ). At block  178 , a deactivation signal is maintained on the first, second, and third sets of pixels  102  while the first, second, and third data signals are supplied to the pixels  102 . As may be appreciated, the deactivation signal may be maintained after programming a frame of data (e.g., data for each line of pixels  102  of the display  18 ), but before a touch mode begins. Accordingly, leakage current of the TFTs  108  of the pixels  102  may be reduced, resulting in improved image quality of the display  18 . 
     It should be noted that the first, second, and third data signals may each be different. For example, the first, second, and third data signals may be separate voltages. Furthermore, the first VCOM may include a first area, the second VCOM may include a second area, and the third VCOM may include a third area. Accordingly, the first area may be greater than the second area, the second area may be greater than the first area, the third area may be greater than the first or second area, and/or the third area may be smaller than the first or second area. In certain embodiments, the first, second, and third data signals may depend at least partially on a difference in size between the first, second, and third areas. In some embodiments, the first VCOM may be configured to provide a touch driving signal, the second VCOM may be configured to sense a touch of the display  18 , and the third VCOM may include a guard rail configured to inhibit direct capacitive coupling from occurring between the first VCOM and the second VCOM. In certain embodiments, the first, second, and third data signals are supplied after a display mode stores a frame of data in the pixels  102  and the first, second, and third data signals are not used to store data in the pixels  102  of the display  18 . 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.