PATENT DOCUMENT

Publication Number: US-8854401-B2
Application Number: US-97976810-A
Country: US
Kind Code: B2

Title: System and method to improve image edge discoloration

Abstract:
Present techniques involve methods and systems for reducing edge discoloration in a display. In one embodiment, the first and last columns of a display are dimmed by adjusting a black mask or reducing transmittance of the relevant pixels. Further, the first and last columns of a display may be entirely covered by the black mask. In some embodiments, using a coupling extrusion on a neighboring sub-pixel can be used to control the coupling between the neighboring sub-pixels to reduce edge discoloration. Display software may also be used to reduce edge discoloration. For example, software may automatically reduce the brightness of the first and last column. In some embodiments, software may be used to detect edges of objects within the display area. Edges of an object are detected, and the last sub-pixel of the background and/or the first sub-pixel of the object are compensated.

Claims:
What is claimed is: 
     
       1. A liquid crystal display (LCD) comprising:
 a plurality of sub-pixels, comprising:
 sub-pixels arranged in a first column on one edge of a display area of the LCD, wherein the sub-pixels in the first column are coupled a first data line; 
 sub-pixels arranged in a last column on an opposite edge of the display area from the first column, wherein the sub-pixels in the last column are coupled to a second data line; and 
 intermediate sub-pixels between the first column and the last column, wherein the sub-pixels arranged in the first column and the sub-pixels arranged in the last column are each configured to transmit less light out of the LCD in response to a first data signal compared to a light transmitted out of the LCD by the intermediate sub-pixels in response to the first data signal, wherein each of the sub-pixels arranged in the first column and each of the sub-pixels arranged in the last column comprises an electrode having a first transmitting area, wherein each of the intermediate sub-pixels comprises an electrode having a second transmitting area, and wherein the first transmitting area is smaller than the second transmitting area. 
 
 
     
     
       2. A liquid crystal display (LCD) comprising:
 a plurality of sub-pixels, comprising:
 sub-pixels arranged in a first column on one edge of a display area of the LCD, with respect to a plane of the LCD; 
 sub-pixels arranged in a last column on an opposite edge of the display area from the first column; and 
 intermediate sub-pixels between the first column and the last column, wherein the sub-pixels arranged in the first column and the sub-pixels arranged in the last column are each configured to transmit less light out of the LCD in response to a first data signal compared to a light transmitted out of the LCD by the intermediate sub-pixels in response to the first data signal, wherein each of the sub-pixels arranged in the first column and each of the sub-pixels arranged in the last column has only two finger electrodes, and wherein each of the intermediate sub-pixels comprises three finger electrodes. 
 
 
     
     
       3. The LCD of  claim 1 , wherein at least one sub-pixel in the plurality of sub-pixels comprises an electrode comprising a coupling extrusion configured to electrically couple with an electrode of an adjacent sub-pixel. 
     
     
       4. The LCD of  claim 3 , wherein the coupling extrusion is configured to reduce edge discoloration in the LCD compared to an LCD not having a coupling extrusion while maintaining image sharpness of the LCD compared to the LCD not having a coupling extrusion. 
     
     
       5. The LCD of  claim 3 , wherein the coupling extrusion increases crosstalk between an activated sub-pixel and a deactivated sub-pixel. 
     
     
       6. A display comprising:
 a pixel matrix comprising a plurality of sub-pixels; 
 a display controller configured to: 
 identify first and second sets of sub-pixel directly adjacent to an edge, wherein the first and second sets of sub-pixels are on opposing sides of the edge; 
 determine a difference between a first set of data signals associated with the first set of sub-pixels and a second set of data signals associated with the second set of sub-pixels, wherein the second set of sub-pixels are directly adjacent to the first set of sub-pixels; 
 determine modified data signals for the first set of sub-pixels based on the difference; and 
 transmit the modified data signals to the first set of sub-pixels and the second set of signals to the second set of sub-pixels, wherein the first set of sub-pixels transmits less light in response to the modified data signals than in response to the first set of data signals. 
 
     
     
       7. The display of claim  6 , wherein the first set of sub-pixels comprises sub-pixels of an object displayed in a display area of the display, wherein the first set of sub-pixels is substantially transmitting light and wherein the second set of sub-pixels is not substantially transmitting light. 
     
     
       8. The display of  claim 6 , wherein the first set of sub-pixels comprises sub-pixels directly adjacent to an object displayed in a display area of the display, wherein the first set of sub-pixels is substantially transmitting light and wherein the second set of sub-pixels is transmitting less light than the first set of sub-pixels. 
     
     
       9. The display of  claim 6 , wherein the pixel matrix comprises display edge sub-pixels, wherein the display edge sub-pixels are connected to a first data line and a last data line, wherein the first data line and the last data line are on opposite edges of the pixel matrix. 
     
     
       10. The display of  claim 9 , comprising a black mask disposed over the pixel matrix, wherein the black mask is configured to cover a first percentage of area of each of a display edge sub-pixel and cover a second percentage of area of each of the plurality of sub-pixels, wherein the first percentage is greater than the second percentage. 
     
     
       11. The display of  claim 9 , wherein each of the plurality of sub-pixels comprises a pixel electrode having a first transmitting area, and each of the display edge sub-pixels comprises a second transmitting area, wherein the first transmitting area is greater than the second transmitting area. 
     
     
       12. The display of  claim 6 , wherein the modified data signals correspond to the first set of data signals reduced by an attenuation factor. 
     
     
       13. The display of  claim 12 , wherein the attenuation factor is a value between 0 and 1. 
     
     
       14. The display of  claim 6 , wherein each of the plurality of sub-pixels comprises a pixel electrode comprising a coupling extrusion configured to electrically couple with a neighboring sub-pixel. 
     
     
       15. The display of  claim 14 , wherein the coupling extrusion is configured to enable significant coupling between a substantially transmitting sub-pixel and an adjacent substantially non-transmitting pixel. 
     
     
       16. A display system, comprising:
 a plurality of sub-pixels arranged to form a display area of the display system; and 
 a display controller configured to:
 drive data signals corresponding to an image frame to each of the plurality of sub-pixels; 
 detect an edge within the image frame, wherein the edge is located between an object displayed in the display area and a background of the display area; 
 drive modified data signals to edge sub-pixels of the plurality of sub-pixels which correspond to the detected edge within the image frame; and 
 drive unmodified data signals to remaining sub-pixels of the plurality of sub-pixels, wherein the edge sub-pixels transmit less light in response to the modified data signals compared to unmodified data signals. 
 
 
     
     
       17. The display system of  claim 16 , wherein the edge comprises a change in light transmittance between a sub-pixel of the object and a sub-pixel of the background, wherein the change in light transmittance is greater than a threshold. 
     
     
       18. The display system of  claim 16 , wherein the edge comprises a change in light transmittance between two sub-pixels of the object, wherein the change in light transmittance is greater than a threshold. 
     
     
       19. A method of reducing edge discoloration in a display having a plurality of sub-pixels, the method comprising:
 identifying an edge in an image frame; 
 detecting edge sub-pixels that are directly adjacent to the edge in the image frame, wherein locations of the edge sub-pixels in the display change during operation of the display; 
 transmitting modified data signals to the edge sub-pixels; and 
 transmitting unmodified data signals to the remaining sub-pixels, wherein the edge sub-pixels transmit less light in response to the modified data signals than in response to the unmodified data signals. 
 
     
     
       20. The method of  claim 19 , wherein the method is performed dynamically during an operation of the display.

Description:
BACKGROUND 
     The present disclosure relates generally to control of a display device. 
     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. 
     Liquid crystal displays (LCDs) are commonly used as screens or displays for a wide variety of electronic devices, including such consumer electronics as televisions, computers, and handheld devices (e.g., cellular telephones, audio and video players, gaming systems, and so forth). Such LCD devices typically provide a flat display in a relatively thin package that is suitable for use in a variety of electronic goods. In addition, such LCD devices typically use less power than comparable display technologies, making them suitable for use in battery-powered devices or in other contexts where it is desirable to minimize power usage. 
     LCDs typically include an LCD panel having, among other things, a plurality of picture elements (pixels) arranged in a matrix to display an image. Each pixel may include sub-pixels (e.g., red, blue, and green sub-pixels) which variably permit light to pass when an electric field is applied to a liquid crystal material in each sub-pixel. However, adjacent columns of sub-pixels in an LCD panel may be susceptible to electrical coupling (also referred to as crosstalk), which may manifest as undesirable visual artifacts in the LCD display. Moreover, due to the arrangement of sub-pixels in a pixel matrix and/or due to the images to be displayed by the LCD, crosstalk may sometimes have non-uniform affects over a display area, resulting in non-uniform visual artifacts in the displayed image. In particular, edge discoloration along edges of a display active area or along edges of a displayed object may result from such crosstalk effects. 
     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. 
     Techniques of the present disclosure relate to systems and methods for reducing edge discoloration in an LCD display. An LCD display typically includes a matrix of pixels, defined by columns and rows of sub-pixels (i.e., red, blue, and green sub-pixels in each pixel). Due to the configuration of a typical pixel matrix, coupling, interference, or other electromagnetic effects may occur between sub-pixel columns. Such effects may result in undesirable visual artifacts such as edge discoloration in the display area and/or edge discoloration in an object displayed on the LCD. Edge discoloration may refer to a non-uniformity in light transmittance through a first sub-pixel column (e.g., a left edge of the display or object) and a last sub-pixel column (e.g., a right edge of the display or object) with respect to the light transmittance through other sub-pixels in the display or in the object (e.g., the sub-pixels between the left and right edges). The non-uniformity in light transmittance may include, for example, a higher light transmittance through the first and last sub-pixel columns of a display or of an object due to relatively higher crosstalk between sub-pixels in the other portions of the display. 
     One or more embodiments involve techniques for dimming the first and last sub-pixel columns of a display to mitigate edge discoloration. For example, to reduce edge discoloration in a display area, a black mask over the first and last columns of sub-pixels may be configured to reduce light transmittance through those sub-pixels, or electrodes in the relevant sub-pixels may be shaped for reduced light transmittance. Furthermore, software may be utilized to automatically reduce the brightness of the first and last sub-pixel columns. Embodiments also include techniques for mitigating edge discoloration in objects displayed on the LCD. In some embodiments, software may be used to detect edges of objects within the display area. Once object edges are detected, the last sub-pixel of the background and/or the first sub-pixel of the object are driven to reduce edge discoloration perceptibility. In some embodiments, each sub-pixel may be configured with a coupling extrusion on the pixel electrode to control a coupling effect between the neighboring sub-pixels to reduce edge discoloration perceptibility. 
    
    
     
       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 block diagram of an electronic device, in accordance with aspects of the present disclosure; 
         FIG. 2  is a perspective view of a computer in accordance with aspects of the present disclosure; 
         FIG. 3  is a perspective view of a handheld electronic device in accordance with aspects of the present disclosure; 
         FIG. 4  is an exploded view of a liquid crystal display (LCD) in accordance with aspects of the present disclosure; 
         FIG. 5  graphically depicts circuitry that may be found in the LCD of  FIG. 4  in accordance with aspects of the present disclosure; 
         FIG. 6  is an illustration of edge discoloration in the display area of the LCD of  FIG. 4  in accordance with aspects of the present disclosure; 
         FIGS. 7A and 7B  are illustrations of edge discoloration in objects displayed by the LCD of  FIG. 4  in accordance with aspects of the present disclosure; 
         FIG. 8  is a diagram representing different sub-pixel schemes in forming different colored objects in a display area, in accordance with aspects of the present disclosure; 
         FIG. 9  is a diagram representing a black mask and the corresponding sub-pixels covered by the black mask, in accordance with aspects of the present disclosure; 
         FIGS. 10A and 10B  are diagrams representing a view of a pixel matrix in the LCD of  FIG. 4  and a view of the black mask over the pixel matrix, in accordance with aspects of the present disclosure; 
         FIG. 11  is a diagram representing finger electrodes in a row of sub-pixels, in accordance with aspects of the present disclosure; 
         FIG. 12  is a diagram representing a detected edge between a black background and a gray object, in accordance with aspects of the present disclosure; 
         FIG. 13  is a diagram representing a detected edge between a yellow object and a black background, in accordance with aspects of the present disclosure; and 
         FIGS. 14A and 14B  compare a finger electrode configuration in a typical sub-pixel with a finger electrode having a coupling extrusion in a sub-pixel configured to reduce edge discoloration. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are 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. 
     Certain embodiments of the present disclosure are generally directed to methods and systems for reducing edge discoloration in an LCD display. Edge discoloration may refer to a non-uniformity in light transmittance through a first sub-pixel column (e.g., a left edge of the display or a displayed object) and a last sub-pixel column (e.g., a right edge of the display or displayed object) with respect to the light transmittance through other sub-pixels in the display or in the object (e.g., the sub-pixels between the left and right edges). The non-uniformity in light transmittance may include, for example, a higher transmittance of light through the first and last sub-pixel columns of a display or of an object due to relatively higher crosstalk effects between sub-pixels in the portions of the display between the first and last sub-pixel columns. 
     Various embodiments include techniques for mitigating edge discoloration in edges of a display area and/or edges of a displayed object. Some embodiments for reducing edge discoloration in display area edges involve dimming the first and last sub-pixel columns of a display area. For example, a black mask over the first and last columns of sub-pixels may be configured to reduce light transmittance, or electrodes in the relevant sub-pixels may be shaped for reduced light transmittance through those sub-pixels. Furthermore, software may be utilized to automatically reduce the brightness of the first and last sub-pixel columns in a display area. Embodiments also include techniques for mitigating edge discoloration in objects displayed on the LCD. In some embodiments, software may be used to detect edges of objects within the display area. Once object edges are detected, the last sub-pixel of the background and/or the first sub-pixel of the object are driven to reduce edge discoloration perceptibility. In some embodiments, each sub-pixel may be configured with a coupling extrusion on the pixel electrode to control a coupling effect between the neighboring sub-pixels to reduce edge discoloration perceptibility. With these foregoing features in mind, a general description of electronic devices including a display that may use the presently disclosed technique is provided below. 
     As may be appreciated, electronic devices may include various internal and/or external components which contribute to the function of the device. For instance,  FIG. 1  is a block diagram illustrating components that may be present in one such electronic device  10 . Those of ordinary skill in the art will appreciate that 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, such as a hard drive or system memory), or a combination of both hardware and software elements.  FIG. 1  is only one example of a particular implementation and is merely intended to illustrate the types of components that may be present in the electronic device  10 . For example, in the presently illustrated embodiment, these components may include a display  12 , input/output (I/O) ports  14 , input structures  16 , one or more processors  18 , one or more memory devices  20 , non-volatile storage  22 , expansion card(s)  24 , networking device (RF circuitry)  26 , and power source  28 . 
     The display  12  may be used to display various images generated by the electronic device  10 . The display  12  may be any suitable display, such as a liquid crystal display (LCD) or an organic light-emitting diode (OLED) display. Additionally, in certain embodiments of the electronic device  10 , the display  12  may be provided in conjunction with a touch-sensitive element, such as a touchscreen, that may be used as part of the control interface for the device  10 . The display  12  may include an LCD panel configured to reduce edge discoloration. In some embodiments, the LCD panel may include a matrix of pixels configured to be driven to mitigate edge discoloration. 
     Processors  18  may provide the processing capability to execute the operating system, programs, user and application interfaces, and any other functions of the electronic device  10 . The processors  18  may include one or more microprocessors, such as one or more “general-purpose” microprocessors, one or more special-purpose microprocessors or ASICS, or some combination of such processing components. For example, the processors  18  may include one or more reduced instruction set (RISC) processors, as well as graphics processors, video processors, audio processors, and the like. As will be appreciated, the processors  18  may be communicatively coupled to one or more data buses or chipsets for transferring data and instructions between various components of the electronic device  10 . 
     Programs or instructions executed by processor(s)  18  may be stored in any suitable manufacture that includes one or more tangible, computer-readable media at least collectively storing the executed instructions or routines, such as, but not limited to, the memory devices and storage devices described below. Also, these programs (e.g., an operating system) encoded on such a computer program product may also include instructions that may be executed by the processors  18  to enable the device  10  to provide various functionalities, including those described herein. 
     The instructions or data to be processed by the one or more processors  18  may be stored in a computer-readable medium, such as a memory  20 . The memory  20  may include a volatile memory, such as random access memory (RAM), and/or a non-volatile memory, such as read-only memory (ROM). The memory  20  may store a variety of information and may be used for various purposes. For example, the memory  20  may store firmware for electronic device  10  (such as basic input/output system (BIOS)), an operating system, and various other programs, applications, or routines that may be executed on electronic device  10 . In addition, the memory  20  may be used for buffering or caching during operation of the electronic device  10 . 
     The components of the device  10  may further include other forms of computer-readable media, such as non-volatile storage  22  for persistent storage of data and/or instructions. Non-volatile storage  22  may include, for example, flash memory, a hard drive, or any other optical, magnetic, and/or solid-state storage media. Non-volatile storage  22  may be used to store firmware, data files, software programs, wireless connection information, and any other suitable data. 
     The electronic device  10  may take the form of a computer system or some other type of electronic device. Such computers may include computers that are generally portable (such as laptop, notebook, tablet, and handheld computers), as well as computers that are generally used in one place (such as conventional desktop computers, workstations and/or servers). In certain embodiments, electronic device  10  in the form of a computer may include a model of a MacBook®, MacBook® Pro, MacBook Air®, iMac®, Mac® mini, or Mac Pro® available from Apple Inc. of Cupertino, Calif. By way of example, an electronic device  10  in the form of a laptop computer  30  is illustrated in  FIG. 2  in accordance with one embodiment. The depicted computer  30  includes a housing  32 , a display  12  (e.g., in the form of an LCD  34  or some other suitable display), I/O ports  14 , and input structures  16 . 
     The display  12  may be integrated with the computer  30  (e.g., such as the display of the depicted laptop computer) or may be a standalone display that interfaces with the computer  30  using one of the I/O ports  14 , such as via a DisplayPort, Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI), or analog (D-sub) interface. For instance, in certain embodiments, such a standalone display  12  may be a model of an Apple Cinema Display®, available from Apple Inc. 
     Although an electronic device  10  is generally depicted in the context of a computer in  FIG. 2 , an electronic device  10  may also take the form of other types of electronic devices. In some embodiments, various electronic devices  10  may include mobile telephones, media players, personal data organizers, handheld game platforms, cameras, and combinations of such devices. For instance, as generally depicted in  FIG. 3 , the device  10  may be provided in the form of handheld electronic device  36  that includes various functionalities (such as the ability to take pictures, make telephone calls, access the Internet, communicate via email, record audio and video, listen to music, play games, and connect to wireless networks). By way of further example, handheld device  36  may be a model of an iPod®, iPod® Touch, or iPhone® available from Apple Inc. In the depicted embodiment, the handheld device  32  includes the display  12 , which may be in the form of an LCD  34 . The LCD  34  may display various images generated by the handheld device  32 , such as a graphical user interface (GUI)  38  having one or more icons  40 . 
     In another embodiment, the electronic device  10  may also be provided in the form of a portable multi-function tablet computing device (not illustrated). In certain embodiments, the tablet computing device may provide the functionality of two or more of a media player, a web browser, a cellular phone, a gaming platform, a personal data organizer, and so forth. By way of example only, the tablet computing device may be a model of an iPad® tablet computer, available from Apple Inc. 
     With the foregoing discussion in mind, it may be appreciated that an electronic device  10  in either the form of a handheld device  30  ( FIG. 2 ) or a computer  50  ( FIG. 3 ) may be provided with a display device  10  in the form of an LCD  34 . As discussed above, an LCD  34  may be utilized for displayed respective operating system and/or application graphical user interfaces running on the electronic device  10  and/or for displaying various data files, including textual, image, video data, or any other type of visual output data that may be associated with the operation of the electronic device  10 . 
     One example of an LCD display  34  is depicted in  FIG. 4  in accordance with one embodiment. The depicted LCD display  34  includes an LCD panel  42  and a backlight unit  44 , which may be assembled within a frame  46 . As may be appreciated, the LCD panel  42  may include an array of pixels configured to selectively modulate the amount and color of light passing from the backlight unit  44  through the LCD panel  42 . For example, the LCD panel  42  may include a liquid crystal layer, one or more thin film transistor (TFT) layers configured to control orientation of liquid crystals of the liquid crystal layer via an electric field, and polarizing films, which cooperate to enable the LCD panel  42  to control the amount of light emitted by each pixel. Additionally, the LCD panel  42  may include a black mask and color filter layer having colored filters that allow specific colors of light to be emitted from the pixels (e.g., red, green, and blue). 
     The backlight unit  44  includes one or more light sources  48 . Light from the light source  48  is routed through portions of the backlight unit  44  (e.g., a light guide and optical films) and generally emitted toward the LCD panel  42 . In various embodiments, light source  48  may include a cold-cathode fluorescent lamp (CCFL), one or more light emitting diodes (LEDs), organic light emitting diodes (OLEDs), or any other suitable source(s) of light. Further, although the LCD  34  is generally depicted as having an edge-lit backlight unit  44 , it is noted that other arrangements may be used (e.g., direct backlighting) in full accordance with the present technique. 
     Referring now to  FIG. 5 , an example of a circuit view of pixel-driving circuitry found in an LCD  34  is provided. For example, the circuitry depicted in  FIG. 5  may be embodied on the LCD panel  42  described above with respect to  FIG. 4 . The pixel-driving circuitry includes an array or matrix  70  of unit pixels  60  that are driven by data (or source) line driving circuitry  66  and scanning (or gate) line driving circuitry  68 . Data signals may be transmitted to the data line driving circuitry  66  and the scanning line driving circuitry  68  by a display controller  72 . As depicted, the matrix  70  of unit pixels  60  (represented by pixels  60   a - 60   f  in this illustration) forms an image display region of the LCD  34 . In such a matrix, each unit pixel  60  may be defined by the intersection of data lines  50  and scanning lines  52 , which may also be referred to as source lines  50  and gate lines  52 . The data line driving circuitry  66  may include one or more driver integrated circuits (also referred to as column drivers) for driving the data lines  50 . The scanning line driving circuitry  68  may also include one or more driver integrated circuits (also referred to as row drivers). By way of example, in a color LCD panel  34  having a display resolution of 960×640, each of the 960 pixel columns may include a group of data lines  50  (e.g., corresponding to red, green, or blue unit pixels in some embodiments), and each data line  50  may include 640 pixel rows. Each data line  50  may correspond to a column of unit pixels  60 . Further, each of the 640 scanning lines  52 , (defining a row in some embodiments) may include 960 groups of unit pixels. For example, some embodiments of the LCD panel  34  may be a model of the Retina™ display, available from Apple Inc. 
     Each unit pixel  60  includes a pixel electrode  54  and thin film transistor (TFT)  56  for switching the pixel electrode  54 . In the depicted embodiment, the source  58  of each TFT  56  is electrically connected to a data line  50 , extending from respective data line driving circuitry  66 . Similarly, in the depicted embodiment, the gate  62  of each TFT  56  is electrically connected to a scanning or gate line  52 , extending from respective scanning line driving circuitry  68 . In one embodiment, column drivers of the data line driving circuitry  66  may send image signals, also referred to as data signals, to the pixels  60  by way of the respective data lines  50 . In some embodiments, the transmission of data signals may be controlled by the display controller  72 . Data signals may be generated by the display controller  72  and transmitted to the data line driving circuitry  66  via a data line  74 . Specifically, the data signals may generally include image data to be processed by data line driving circuitry  66  of the LCD  34  to drive the pixels  60  and render an image on the LCD  34 . 
     The scanning lines  52  may apply scanning signals from the scanning line driving circuitry  68  to the respective gates  62  of each TFT  56  to which the respective scanning lines  52  are connected. Such scanning signals may be applied by line-sequence with a predetermined timing or in a pulsed manner. Each TFT  56  serves as a switching element which may be activated and deactivated (i.e., turned on and off) for a predetermined period based on the respective presence or absence of a scanning signal at its gate  62 . When activated, a TFT  56  may store the data signals received via a respective data line  50  as a charge in the pixel electrode  54  with a predetermined timing. 
     The data signal may be stored at the pixel electrode  54  and used to generate an electrical field between the respective pixel electrode  54  and a common electrode. Such an electrical field may align liquid crystals within a liquid crystal layer to modulate light transmission through the LCD panel  42 . In some embodiments, each unit pixel electrode  54  may include a number of “finger” electrodes, i.e. strips of electrode plates which are electrically connected as a unit pixel  60 . For example, a unit pixel  60  may have one or multiple parallel finger electrodes, and in other embodiments, other configurations may be possible. Further, in some embodiments, a storage capacitor may also be provided in parallel to the liquid crystal capacitor formed between the pixel electrode  54  and the common electrode to prevent leakage of the stored image signal at the pixel electrode  54 . For example, such a storage capacitor may be provided between the drain  64  of the respective TFT  56  and a separate capacitor line. 
     Unit pixels  60  may operate in conjunction with various color filters, such as red, green, and blue filters. In such embodiments, a “pixel” of the display may actually include multiple unit pixels, also referred to as sub-pixels, such as a red sub-pixel (e.g.,  60   a ), a green sub-pixel (e.g.,  60   b ), and a blue sub-pixel (e.g.,  60   c ), each of which may be modulated to increase or decrease the amount of light emitted to enable the display to render numerous colors via additive mixing of the colors. 
     However, due to the proximity of sub-pixels  60  along the direction of the gate lines  52  (x-direction), each sub-pixel  60  may be affected by crosstalk, which may refer to electrical coupling and other electromagnetic effects between adjacent sub-pixels  60  along the x-direction. Specifically, the electric field generated at each sub-pixel  60  in response to the data signals driven through the respective data lines  50  may affect the electric field generated at an adjacent sub-pixel  60  in the x-direction, thereby affecting the alignment of liquid crystals in the liquid crystal layer of the affected sub-pixels  60  and reducing the transmittance of light through the LCD panel  42 . 
     Due to the configuration of sub-pixels  60  in the pixel matrix  70 , certain portions of a display area in an LCD  34  may be affected by crosstalk differently. For example, each of the sub-pixels  60  connected to a first data line  50   1  may only be affected by crosstalk from one adjacent sub-pixel  60  (e.g., sub-pixels  60  connected to the second data line  50   2 ) along the x-direction. Similarly, sub-pixels  60  connected to a last data line  50   n  may also only be affected by crosstalk from one adjacent sub-pixel  50   n−1  in the x direction. However, the other sub-pixels  60  of the pixel matrix  70  between the first and last data line  50   1  and  50   n , such as the sub-pixels  60  connected to the data lines  50   2 ,  50   3 , and  50   4 , may be affected by crosstalk between one adjacent sub-pixel  60  on either side in the x-direction. Therefore, the sub-pixels  60  between the first and last data line  50   1  and  50   n  are affected by crosstalk from two adjacent sub-pixels  60 , rather than just one. As the sub-pixels  60  of the first and last data lines  50   1  and  50   n  are generally less affected by less crosstalk (e.g., by about one half) compared to the sub-pixels  60  having two adjacent sub-pixels  60  along the x-direction, the sub-pixels  60  of the first and last data lines  50   1  and  50   n  may generally transmit a greater amount of light than other sub-pixels  60  in the display area. Such effects may be perceived as greater light transmission at the y-direction edges (parallel to the data lines  50 ), or the edges of the display area over data lines  50   1  and  50   n . 
     Moreover, as the same color of a color filter may typically be associated with the sub-pixels  60  connected to a common data line  50 , variations in light transmittance may also affect the chromaticity of the LCD panel  42 . The higher light transmission at the y-direction edges (e.g., along the data lines  50   1  and  50   n ), referred to as edges, may manifest as edge discolorations along the display area edges, as illustrated in  FIG. 6 . For example, a pixel typically includes a red sub-pixel  60   a , a green sub-pixel  60   b , and a blue sub-pixel  60   c  arranged in a red-green-blue order with respect to the x-direction. As such, a first data line  50   1  may typically be connected to red sub-pixels  60 , and a last data line  50   n  may typically be connected to blue sub-pixels  60 . As the sub-pixels  60  of the first and last data lines  50   1  and  50   n  may generally have higher light transmittance due to uneven crosstalk effects, the edges  82  and  84  of a display area  80  may appear red at a first edge  82  and blue at a last edge  84  (also referred to as left edge  82  and right edge  84 , respectively). 
     Furthermore, different portions of the display area may be affected by crosstalk differently depending on the image being displayed by the LCD  34 . Crosstalk effects are generally more perceivable between two “ON” sub-pixels  60 , or two activated sub-pixels  60  storing an electric field in response to a received image signal. For example, ON sub-pixels  60  may correspond with sub-pixels  60  which align the liquid crystal layer to transmit light, while “OFF” sub-pixels  60  may be deactivated and/or may correspond with sub-pixels  60  transmitting little or no light. The display controller  72  may sometimes drive a group of ON sub-pixels  60  adjacent to a group of OFF sub-pixels  60 , such as when displaying an colored object in a black background. Due to the positioning of ON and OFF sub-pixels in the display area, areas of the display area may be differently affected by crosstalk, resulting in a non-uniform light transmission over the display area, such as higher light transmission at the y-direction edges (i.e., between adjacent ON sub-pixel  60  and OFF sub-pixels) of displayed objects. 
     Higher light transmission at the edges of displayed objects may also manifest as edge discoloration, as illustrated in  FIGS. 7A and 7B .  FIG. 7A  illustrates a display  12  displaying an object  86   a  in a display area  80   a . The remaining portions of the display area  80   a  around the object  86   a  may be a white background  92   a . To display white, the red, blue, and green sub-pixels  60  in the background  92   a  may all be transmitting light and may be in an ON state. In the illustrated example, the object  86   a  may be gray colored, such that the red, blue, and green sub-pixels  60  may be partially transmitting light (e.g., between an ON and OFF state). As crosstalk effects may be generally more perceptible between sub-pixels  60  in an ON state, the sub-pixels  60  transmitting the white background  92   a  which are adjacent to the sub-pixels  60  transmitting the gray object  86   a  may be less affected by crosstalk compared to other sub-pixels  60  which are adjacent to an ON sub-pixel on each side. This may result in higher light transmission through the sub-pixels  60  directly adjacent to the first edge  88   a  of the object  86   a  and the sub-pixels  60  directly adjacent to the last edge  90   a  of the object  86   a  (also referred to as the left edge  88   a  and the right edge  90   a , respectively). In a red-green-blue pixel configuration, the ON sub-pixels  60  of the white background  92   a  may have reduced crosstalk effects, resulting in higher light transmission through the blue sub-pixels  60  directly adjacent to the left edge  88   a  and through the red sub-pixels  60  directly adjacent to the right edge  90   a.    
       FIG. 7B  illustrates a display  12  displaying an object  86   b  in a display area  80   b . The remaining portions of the display area  80   b  around the object  86   b  may be a black background  92   b . To display black, the red, blue, and green sub-pixels  60  in the background  92   b  may not transmit light and may be in an OFF state. In the illustrated example, the object  86   b  may be gray colored, such that the red, blue, and green sub-pixels  60  may be partially transmitting light (e.g., between an ON and OFF state). As crosstalk effects may be generally more perceptible between sub-pixels  60  in an ON state, the sub-pixels  60  of the black background  92   b  may not generally be affected by crosstalk, and the sub-pixels  60  transmitting the gray object  86   b  which are adjacent to the black background  92   b  may be less affected by crosstalk compared to other sub-pixels  60  in the object  86   b  which are not adjacent to OFF sub-pixels  60 . This may result in higher light transmission through the sub-pixels  60  in the first edge  88   b  of the object  86   b  and in the last edge  90   b  of the object  86   b  (also referred to as the left edge  88   b  and the right edge  90   b , respectively). In a red-green-blue pixel configuration, the sub-pixels  60  of the gray object  86   b  may have reduced crosstalk effects, resulting in higher light transmission through the red sub-pixels  60  at the left edge  88   b  and through the blue sub-pixels  60  at the right edge  90   b.    
     While gray objects  86   a  and  86   b  are used to explain edge discoloration in the examples of  FIGS. 7A and 7B , edge discoloration may also be perceivable when displaying objects of other colors, as explained in the diagram  FIG. 8 . The diagram of  FIG. 8  includes rows  98 ,  100 ,  102 , and  104 , which each represents a displayed object  86  in a background  92 . The object  86  represented in each of the rows  98 ,  100 ,  102 , and  104  is in a background  92  of a display area  80 , and each of the objects  86  has a first pixel column  94  and a last pixel column  96 , each including red, blue, and green sub-pixels. In each of the rows  98 ,  100 ,  102 , and  104 , the heavy shading represents little or no light transmission (e.g., OFF state) through the sub-pixels  60 , the light shading represents partial light transmission (e.g., between OFF and ON states) through the sub-pixels  60 , and no shading represents significant light transmission (e.g., ON state) through the sub-pixels  60 . For example, row  98  represents a gray object  86  displayed in a black background, as discussed with respect to  FIG. 7B , and row  100  represents a gray object  86  in a white background, as discussed with respect to  FIG. 7A . 
     Row  102  represents a yellow object  86  in a black background  92 . To transmit a perceived yellow color from the LCD  34 , the red and green sub-pixels of the yellow object  86  may be ON and transmitting light, while the blue sub-pixel may be OFF. However, because the red sub-pixel  60  of the first pixel column  94  is adjacent to the black background  92 , the red sub-pixel  60  may be less affected by crosstalk, and may have greater light transmission, such that the first edge of the yellow object  86  appears reddish. Similarly, the green sub-pixel  60  of the last column  96  is adjacent to the blue sub-pixel  60  which is in an OFF state. Thus, the green sub-pixel  60  of the last column  96  may be less affected by crosstalk and have greater light transmission, such that the last edge of the yellow object  86  appears greenish. Similarly, row  104  represents a magenta object  86  on a black background  92 , and due to the reduced crosstalk effects and higher light transmission through the red sub-pixel  60  of the first pixel column  94  and through the blue sub-pixel  60  of the last pixel column  96 , the magenta object  86  may appear to have a reddish first edge and a bluish last edge. 
     One or more embodiments provide techniques for reducing the perceptibility of edge discoloration at the left and right edges  82  and  84  of a display area  80  and/or at the left and right edges  88  and  90  of an object  86  displayed in a display area  80 . Various embodiments are provided in  FIGS. 9-14 , wherein  FIGS. 9-11  provide embodiments directed towards reducing edge discoloration in the edges  82  and  84  of a display area  80 , and  FIGS. 12-14  provide embodiments directed towards reducing edge discoloration in edges  88  and  90  of a displayed object  86 . 
     Beginning first with  FIG. 9 , one embodiment for reducing edge discoloration at the left and right edges  82  and  84  of a display area  80  includes configuring a black mask  108  to decrease the amount of light transmitted through the sub-pixels  60  connected to the first and last data lines  50   1  and  50   n  of a pixel matrix  70 . One row of sub-pixels  60  and a corresponding portion of a black mask  108  is represented in  FIG. 9 , where the portions of the black mask over the first red sub-pixel  60   1  and the last blue sub-pixel  60   n  may be configured to cover a greater area of each of the first and last sub-pixels  60   1  and  60   n . Covering more of light-transmitting areas of the first and last sub-pixels  60   1  and  60   n  connected to the first and last data lines  50   1  and  50   n  may compensate for the effect of higher light transmission through the sub-pixels  60   1  and  60   n  due to comparatively less crosstalk effects, which may reduce the perceptibility of edge discoloration at the edges  82  and  84 . In different embodiments, the black mask  108  may be configured to cover any percentage of the first and last sub-pixels  60   1  and  60   n , depending on the configuration of the LCD  34  and/or the predicted transmission of light through first and last sub-pixels  60   1  and  60   n . Furthermore, in some embodiments, more than the first and last sub-pixels  60   1  and  60   n  may be configured for reduced light transmittance. For example, in some embodiments, the black mask  108  may also be configured to reduce light transmission through the sub-pixels  60   2  and  60   n−1 . 
     In some embodiments, the black mask  108  may be configured to completely cover a first and last column of “dummy” sub-pixels  60 , as illustrated in  FIGS. 10A and 10B . As provided in  FIG. 10A , the pixel matrix  70  may include an additional column of dummy sub-pixels connected to data lines  50   0  and  50   n+1 . The sub-pixels connected to data lines  50   0  and  50   n+1  may be driven with the same or similar data gray scale level as the adjacent sub-pixels  60  (e.g., sub-pixels  60  connected to data lines  50   1  and  50   n ), but the black mask  108  may completely cover these sub-pixels  60 , as shown in  FIG. 10B , such that the sub-pixels  60  which are visible at the edges  82  and  84  may have the same crosstalk effects and similar light transmittance properties as other sub-pixels  60  in the display area  80 , thus reducing the perceptibility of edge discoloration. 
     Another embodiment for reducing edge discoloration at the left and right edges  82  and  84  of a display area  80  is provided in  FIG. 11 , which represents one row of sub-pixels  60 , including a sub-pixel  60   1  connected to a first data line  50   1  and a sub-pixel  60   n  connected to a last data line  50   n . The finger electrodes  110  in the first and last sub-pixels  60   1  and  60   n  may be configured for reduced light transmittance. As the area of the pixel electrode  54  generally correlates with the light-transmitting area of the pixel  60 , reducing the number of finger electrodes  110  in the pixel electrodes  54  of the first and last sub-pixels  60   1  and  60   n  may reduce light transmission of those sub-pixels  60   1  and  60   n  in comparison with other sub-pixels  60 , thereby compensating for the increased light transmission through the first and last sub-pixels  60   1  and  60   n  and reducing the edge discoloration at the left and right edges  82  and  84  of the display area  80 . For example, in some embodiments, sub-pixels  60  may typically have 3 finger electrodes  110 , and the first and last sub-pixels  60   1  and  60   n  may each have 2 finger electrodes  110 . In different embodiments, other finger electrode configurations are also possible (e.g., thinner finger electrodes, or differently shaped finger electrodes). Furthermore, in some embodiments, more than the first and last sub-pixels  60   1  and  60   n  may be configured for reduced light transmittance. For example, in some embodiments, the finger electrodes  110  in sub-pixels  60   2  and  60   n−1  may also be configured for reduced light transmittance. 
     In some embodiments, the brightness of the sub-pixels  60  connected to the first and last data lines  50   1  and  50   n  may be automatically reduced by using software. For example, the display controller  72  ( FIG. 5 ) may send a data signal to the red, green, and blue sub-pixels [R 1 , G 1 , B 1 ] and [R n , G n , B n ] of a first and last pixel column, respectively, using the relationships [R 1 *x, G 1 , B 1 ] and [R n , G n , B n *k], where x and k may be the same or different, and are attenuation factors having values between 0 and 1. By reducing the brightness of the red and blue sub-pixels  60  of the first and last data lines  50   1  and  50   n , the display controller  72  may automatically reduce the perceptibility of edge discoloration without any changes to the hardware or design of the LCD  34 . In some embodiments, the values x and k may be determined empirically, and may also be determined dynamically during an operation of the LCD  34 . Further, in some embodiments, more than the first and last data lines  50   1  and  50   n  may be adjusted. For example, the relationship [R 1 *x, G 1 *y, B 1 ] and [R n , G n *j, B n *k] may be used to compensate for edge discoloration at the first and last two data lines  50 . 
     The present techniques may also include embodiments for reducing edge discoloration at the edges  88  and  90  of a displayed object  86 , as will be discussed with respect to  FIGS. 12-14 . In one embodiment, the data signals corresponding to the edges  88  and/or  90  of an object  86  may be modified to reduce edge discoloration. For example a gray object  86  may be displayed in a black background  92 , as illustrated in  FIG. 12 . Potential edge discoloration may be detected by detecting abrupt edges in a display area. For example, the display controller  12  (or another suitable controller coupled to the display controller  12 ) may determine an abrupt edge when the blue sub-pixel  60  of one pixel  112  and the red sub-pixel  60  of an adjacent pixel  114  are driven by data signals having a difference greater than a threshold value. The threshold may be determined empirically depending on the configuration of the LCD  34  and/or on the images to be displayed by the LCD  34 . In some embodiments, if the difference between blue sub-pixel  60  of the pixel  112  and the red sub-pixel  60  of the pixel  114  is greater than the threshold, the last sub-pixel  60  of the background pixel  112  and the first sub-pixel  60  of the object pixel  114  may be compensated according to [R 112 , G 112 , B 112 *C 1 ] and [R 114 *C 2 , G 114 , B 114 ], where C 1  and C 2  may be the same or different, and may each be greater than 0 and less than 1. The values C 1  and C 2  may be determined to reduce the difference between the adjacent sub-pixels  60  corresponding to the abrupt edges, such that potential edge discoloration resulting from the abrupt edges may be reduced. In some embodiments, a similar compensation may be applied to a detected abrupt edge from the transition of the object  86  to the background  92 . 
     In some embodiments, abrupt edges may also be detected when the difference in data signals is not detected between the last sub-pixel  60  of a background pixel and the first sub-pixel  60  of an object pixel. For example, as illustrated in  FIG. 13 , the object  86  may be yellow (e.g., transmitting through the red and green sub-pixels  60 ) and in a black background  92 . Since the blue sub-pixels  60  of the object  86  are substantially in an OFF state, an abrupt edge may be detected between the ON green sub-pixel  60  and the OFF blue sub-pixel  60  of the pixel  116 . If the difference between the green sub-pixel  60  and the blue sub-pixel  60  of the pixel  116  is greater than a threshold, the pixel  116  may be compensated according to [R 116 , G 116 *C 3 , B 116 *C 4 ], where C 3  and C 4  may each be greater than 0 and less than 1. 
     One or more embodiments may also involve configuring the shape of sub-pixel electrodes  54  such that each sub-pixel  60  may have a controlled coupling effect with its adjacent sub-pixels  60 . The controlled coupling effect may increase coupling between two adjacent sub-pixels  60  when one of the sub-pixels  60  is in an ON state and when its adjacent sub-pixel is in an OFF state. By increasing coupling between a pair of ON and OFF adjacent sub-pixels, light transmission may be reduced through the ON sub-pixel and/or increased through the OFF sub-pixel, thereby reducing possible edge discoloration. 
     For example, in some embodiments as provided in  FIGS. 14A and 14B , each sub-pixel electrode  54  may include a coupling extrusion designed to result in an amount of coupling that reduces edge discoloration while preserving desirable visual attributes. The diagram of  FIG. 14A  provides a typical configuration of finger electrodes  110  in two adjacent sub-pixels  60 . As crosstalk is greater when a sub-pixel  60  is in an ON state, crosstalk may generally occur between the finger electrodes  110  of the ON state sub-pixel, and may not occur at the finger electrodes  110  of the OFF sub-pixel. As discussed, sub-pixels  60  adjacent to OFF sub-pixels may be less affected by crosstalk, and may transmit more light than other ON sub-pixels, possibly resulting in edge discoloration. The diagram of  FIG. 14B  provides one embodiment of finger electrodes  110  including a coupling extrusion  120 . The coupling extrusion  120  may be an extension of the finger electrodes  110  and configured to increase coupling between ON and OFF sub-pixels  60 . Increasing coupling between ON and OFF sub-pixels  60  may reduce light transmission through the ON sub-pixel  60  and increase light transmission through the OFF sub-pixel  60 , thus reducing the perceptibility of edge discoloration. 
     In different embodiments, different combinations of the above techniques may be used. Though embodiments directed to display area edge discoloration ( FIGS. 9-11 ) and displayed object edge discoloration ( FIG. 12-14 ) are separately presented, any of the techniques may be combined. For example, a black mask  108  may be adjusted for the sub-pixels  60  connected to the first and last data lines  50   1  and  50   n , and all sub-pixels  60  may be configured with a coupling extrusion  120 . Furthermore, software compensation may also be used in conjunction with any hardware modifications. 
     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.

Metadata:
Filing Date: 20101228
Publication Date: 20141007
Grant Date: 20141007
Priority Date: 20101228
Inventors: CHEN CHENG
CHANG SHIH CHANG
GU MINGXIA
ZHONG JOHN Z.
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2300/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0232", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3648", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/0209", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/061", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0242", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0242", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0232", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0209", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/061", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3648", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 46316062