PATENT DOCUMENT

Publication Number: US-10096284-B2
Application Number: US-201615270952-A
Country: US
Kind Code: B2

Title: System and method for external pixel compensation

Abstract:
An electronic device includes a display panel. The display panel includes a number of pixels, each of which includes a driving thin-film-transistor (TFT) and a light-emitting diode. Compensation circuitry external to the display panel applies offset data to pixel data for each pixel of the plurality of pixels before the pixel data is provided to the plurality of pixels.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display panel, comprising:
 a plurality of pixels, each pixel of the plurality of pixels comprising:
 a driving thin-film-transistor (TFT) configured to receive pixel data of a respective pixel; and 
 a light-emitting diode configured to emit light based on the pixel data provided to the respective pixel; and 
 
 
 a processing unit, comprising:
 a gamma digital-to-analog converter (DAC) configured to receive pixel data; 
 an offset DAC configured to receive offset data; 
 a feedback path comprising a programmable resistor, wherein the feedback path comprises an output from the offset DAC; and 
 a driver integrated circuit (IC) configured to provide compensated pixel data by adding an output of the gamma DAC and an output of the feedback path, wherein the driver IC is configured to apply the compensated pixel data to each pixel of the plurality of pixels, wherein the light-emitting diode is configured to emit light based upon the compensated pixel data. 
 
 
     
     
       2. The electronic device of  claim 1 , further comprising a processing unit, wherein the offset data is added to the pixel data in a system on a chip (SOC), resulting in offset pixel data. 
     
     
       3. The electronic device of  claim 2 , wherein the electronic device is configured to map the offset pixel data to a gamma domain in the processing unit, resulting in offset gray level data to be provided to the display panel. 
     
     
       4. The electronic device of  claim 3 , wherein the gamma DAC configured to convert the offset gray level data into voltage data; and
 wherein the voltage data is applied to the driving TFT, resulting in a current that is applied to the light-emitting diode, resulting in light emission by the light-emitting diode. 
 
     
     
       5. The electronic device of  claim 1 , wherein the compensated pixel data comprises compensated voltage measurements that are applied to the driving TFT, resulting in a current that is applied to the light-emitting diode, resulting in light emission by the light-emitting diode. 
     
     
       6. The electronic device of  claim 1 , comprising:
 one or more operational amplifiers configured to add the output of the gamma DAC and the output of the offset DAC. 
 
     
     
       7. The electronic device of  claim 1 , wherein the compensated pixel data comprises compensated current measurements that are converted to compensated voltage measurements that are applied to the driving TFT, resulting in a current that is applied to the light-emitting diode, resulting in light emission by the light-emitting diode. 
     
     
       8. The electronic device of  claim 1 , comprising a second programmable resistor disposed in the feedback path, wherein the output of the offset DAC is segmented into a plurality of currents provided to the feedback path. 
     
     
       9. A method of operating an electronic device with a display panel, comprising:
 applying offset data to pixel data for each pixel of a plurality of pixels of the display panel of the electronic device, prior to provision of the pixel data to the plurality of pixels, resulting in compensated pixel data by:
 providing the pixel data to a gamma digital-to-analog converter (DAC) of a source driver; and 
 providing the offset data to an offset DAC of the source driver, wherein an output of the gamma DAC is configured to interest a feedback path comprising a programmable resistor to create a current, wherein the source driver is configured to provide the compensated pixel data by adding the current to an output of the offset DAC; 
 
 applying, at a driving thin-film-transistor (TFT) of each of the plurality of pixels, compensated voltage data that is based upon the compensated pixel data, resulting in a compensated current; and 
 applying the compensated current to a corresponding diode of each of the plurality of pixels. 
 
     
     
       10. The method of  claim 9 , comprising applying the offset data to the pixel data in a processing unit of the electronic device. 
     
     
       11. The method of  claim 9 , comprising applying the offset data to the pixel data in a driving integrated circuit (IC) of the electronic device. 
     
     
       12. The method of  claim 11 , comprising:
 when the compensated pixel data includes a current, converting the current to a compensated voltage. 
 
     
     
       13. An electronic display circuitry, comprising:
 a display panel having a processing unit, the processing unit comprising:
 a gamma digital-to-analog converter (DAC) configured to receive pixel data; 
 an offset DAC configured to receive offset data; 
 a first driver integrated circuit (IC) configured to receive a halved output from the gamma DAC; and 
 a feedback path comprising a first programmable resistor, wherein the feedback path is configured to receive, through an electrical coupling to a second programmable resistor, a doubled voltage output from the offset DAC; and 
 
 wherein the processing unit is configured to apply offset data from the first driver IC to pixel data for each pixel of a plurality of pixels of the display panel, prior to provision of the pixel data to the plurality of pixels, such that a compensated voltage is applied to a driving thin-film-transistor (TFT) of each pixel, resulting in a compensated current that is applied to a light-emitting diode of each pixel. 
 
     
     
       14. The electronic display circuitry of  claim 13 , comprising a second driver IC, comprising the processing unit. 
     
     
       15. The electronic display circuitry of  claim 13 , wherein the first driver IC comprises the offset DAC. 
     
     
       16. The electronic display circuitry of  claim 15 , wherein the offset DAC, the gamma DAC, or both are configured to operate in a current mode to output a current. 
     
     
       17. The electronic display circuitry of  claim 16 , comprising:
 current conversion circuitry configured to convert the current to the compensated voltage.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Non-Provisional Patent Application of U.S. Provisional Patent Application No. 62/357,059, entitled “SYSTEM AND METHOD FOR EXTERNAL PIXEL COMPENSATION”, filed Jun. 30, 2016, which are herein incorporated by reference. 
     BACKGROUND 
     This disclosure relates to external compensation for shifts in operational parameters in display panels. More specifically, the current disclosure relates to performing external compensation when these operational parameters shift. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, 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. 
     Numerous electronic devices include electronic displays, which display images by varying the amount of light that is emitted from an array of pixels of different colors. For pixels that use self-emissive elements, such as organic light emitting diodes (OLEDs), pixel non-uniformities may arise due to light-emitting diode (LED) voltage changes (e.g., Voled), and/or LED current changes (e.g., Ioled). These pixel non-uniformities could produce a degradation in image quality as pixels change over time. Changes in the pixels may be caused by many different factors. For example, changes in the pixels may be caused by temperature changes of the display, an aging of the display (e.g., aging of the thin-film-transistors (TFTs)), the operation of certain display processes, and other factors. 
     To counteract image degradation caused by changes in the display, it may be desirable to implement in-pixel or per-pixel compensation for the changes. Yet as pixels per inch (PPI) increase, in-pixel or per-pixel compensation logic for these changes may become more and more limited. For example, high pixel-per-inch displays may include a smaller pixel circuit footprint. Thus, a size of the in-pixel or per-pixel compensation circuits may become a limiting factor. Further, timing constraints for these high-PPI displays may result timing limitations on the in-pixel or per-pixel compensation circuits. 
     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. 
     To improve image quality and consistency, external compensation circuitry may be used to counter-act negative artifacts caused by variations (e.g., threshold voltage (Vth) shifts) within a pixel. Further, the external compensation circuitry may be used to counter-act negative artifacts from light-emitting diode (LED) (e.g., organic light-emitting diode) voltage shifts that may occur over time. In the current embodiments, lines carrying a data voltage (Vdata) and/or an reference voltage (Vref) may be used to sense the threshold voltages (Vth), LED voltages (Voled) and/or an LED current (e.g., Ioled) that may be used for subsequent compensation that is external to the pixel circuitry. For example, offset data based upon Vth, Voled and/or Ioled values may be used in compensation logic that adjusts a display output based upon inconsistencies between pixels of a display. 
     As mentioned above, in-pixel compensation may be used to correct pixel non-uniformity. Such compensation may utilize a capacitor of the pixel to store data relating to the pixel. This stored data may then be used for pixel compensation in a separate step. Unfortunately, in-pixel compensation may, at times, be slow, utilizing a significant amount of time to store data and then utilize the data for pixel compensation. Additionally, the hardware requirements for in-pixel compensation may be significant for certain electronic devices (especially electronic devices with a small integrated circuit footprint). For example, the storage capacitor used to store the pixel information may be quite large, requiring a significant amount of circuitry area of a limited integrated circuit footprint. 
     Accordingly, in some embodiments described herein, external compensation techniques may obtain certain information about the display panel and alter the input data that is provided to display panel, prior to reaching the display panel (e.g., external to the pixel circuitry). The alterations of the input data effectively compensate for non-uniformity based upon the information obtained about the display panel. For example, non-uniformity that may be corrected using the current techniques may include: neighboring pixels that have similar data, but different luminance, color non-uniformity between neighboring pixels, pixel row inconsistencies, pixel column inconsistencies, etc. As will be discussed in more detail below, an offset digital-to-analog-converter may be used to apply offset data to pixel data, resulting in externally compensated pixel data for implementation on the display panel. 
     Various refinements of the features noted above may exist 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 including a display, 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 , in accordance with an embodiment; 
         FIG. 3  is a front view of a hand-held device representing another embodiment of the electronic device of  FIG. 1 , in accordance with an embodiment; 
         FIG. 4  is a front view of another hand-held device representing another embodiment of the electronic device of  FIG. 1 , in accordance with an embodiment; 
         FIG. 5  is a front view of a desktop computer representing another embodiment of the electronic device of  FIG. 1 , in accordance with an embodiment; 
         FIG. 6  is a front view of a wearable electronic device representing another embodiment of the electronic device of  FIG. 1 , in accordance with an embodiment; 
         FIG. 7  is a circuit diagram illustrating a portion of a matrix of pixels of the display of  FIG. 1 , in accordance with an embodiment; 
         FIG. 8  is a schematic diagram illustrating a process for external compensation of pixels and subsequent processing at the display panel, in accordance with an embodiment; 
         FIG. 9  is a schematic diagram illustrating offset data applied in the driver integrated circuit, in accordance with an embodiment; 
         FIG. 10  is a schematic diagram illustrating application of offset data in the current domain, in accordance with an embodiment; 
         FIG. 11  is a schematic diagram illustrating circuitry that applies offset data in source driver, in accordance with an embodiment; 
         FIG. 12  is a schematic diagram illustrating a more granular version of the embodiment depicted in  FIG. 11 , in accordance with an embodiment; and 
         FIG. 13  is a circuit diagram illustration a second phase of voltage sensing, 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 may 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 additional embodiments that also incorporate the recited features. 
     This disclosure relates to external compensation for non-uniformity that may occur in in display panels. More specifically, the current embodiments describe techniques for external-to-the-pixel application of offset data, where the offset data describes the non-uniformity at a pixel level. 
     Turning first to  FIG. 1 , an electronic device  10  according to an embodiment of the present disclosure may include, among other things, a processor core complex  12  having one or more processor(s), 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 electronic device  10 . 
     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 , the desktop computer depicted in  FIG. 4 , the wearable electronic device depicted in  FIG. 5 , or similar devices. It should be noted that the processor core complex  12  and/or other data processing circuitry may be generally referred to herein as “data processing circuitry.” Such 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 . 
     In the electronic device  10  of  FIG. 1 , the processor core complex  12  and/or other data processing circuitry may be operably coupled with the memory  14  and the nonvolatile storage  16  to perform various algorithms. Such programs or instructions executed by the processor core complex  12  may be stored in any suitable article of manufacture that may include 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 core complex  12  to enable the electronic device  10  to provide various functionalities. 
     As will be discussed further below, the display  18  may include pixels such as organic light emitting diodes (OLEDs), micro-light-emitting-diodes (μ-LEDs), or any other light emitting diodes (LEDs). Further, the display  18  is not limited to a particular pixel type, as the circuitry and methods disclosed herein may apply to any pixel type. Accordingly, while particular pixel structures may be illustrated in the present disclosure, the present disclosure may relate to a broad range of lighting components and/or pixel circuits within display devices. 
     As discussed in more detail below, external compensation circuitry  19  may alter display data that is fed to the display  18 , prior to the display data reaching this display  18  (or a pixel portion of the display  18 ). This alteration of the display data may effectively compensate for non-uniformities of the pixels of the display  18 . For example, non-uniformity that may be corrected using the current techniques may include: neighboring pixels that have similar data, but different luminance, color non-uniformity between neighboring pixels, pixel row inconsistencies, pixel column inconsistencies, etc. 
     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) or wireless local area network (WLAN), such as an 802.11x Wi-Fi network, and/or for a wide area network (WAN), such as a  3rd  generation (3G) cellular network,  4th  generation (4G) cellular network, or long term evolution (LTE) cellular network. The network interface  26  may also include interfaces for, for example, broadband fixed wireless access networks (WiMAX), mobile broadband Wireless networks (mobile WiMAX), asynchronous digital subscriber lines (e.g., 15SL, VDSL), digital video broadcasting-terrestrial (DVB-T) and its extension DVB Handheld (DVB-H), ultra Wideband (UWB), alternating current (14) power lines, and so forth. 
     In certain embodiments, the electronic device  10  may take the form of a computer, a portable electronic device, a wearable electronic device, 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 A, is illustrated in  FIG. 2  in accordance with one embodiment of the present disclosure. The depicted computer  30 A may include a housing or enclosure  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 A, such as to start, control, or operate a GUI or applications running on computer  30 A. For example, a keyboard and/or touchpad may allow a user to navigate a user interface or application interface displayed on display  18 . 
       FIG. 3  depicts a front view of a handheld device  30 B, 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. 
     The handheld device  30 B 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  39 . The indicator icons  39  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, an I/O port for a hard wired connection for charging and/or content manipulation using a standard connector and protocol, such as the Lightning connector provided by Apple Inc., a universal service bus (USB), or other similar connector and protocol. 
     User input structures  42 , in combination with the display  18 , may allow a user to control the handheld device  30 B. For example, the input structure  40  may activate or deactivate the handheld device  30 B, the input structure  42  may navigate user interface to a home screen, a user-configurable application screen, and/or activate a voice-recognition feature of the handheld device  30 B, the input structures  42  may provide volume control, or may toggle between vibrate and ring modes. The input structures  42  may also include a microphone may obtain a user&#39;s voice for various voice-related features, and a speaker may enable audio playback and/or certain phone capabilities. The input structures  42  may also include a headphone input may provide a connection to external speakers and/or headphones. 
       FIG. 4  depicts a front view of another handheld device  30 C which represents another embodiment of the electronic device  10 . The handheld device  30 C may represent, for example, a tablet computer, or one of various portable computing devices. By way of example, the handheld device  30 C 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. of Cupertino, Calif. 
     Turning to  FIG. 5 , a computer  30 D may represent another embodiment of the electronic device  10  of  FIG. 1 . The computer  30 D may be any computer, such as a desktop computer, a server, or a notebook computer, but may also be a standalone media player or video gaming machine. By way of example, the computer  30 D may be an iMac®, a MacBook®, or other similar device by Apple Inc. It should be noted that the computer  30 D may also represent a personal computer (PC) by another manufacturer. A similar enclosure  36  may be provided to protect and enclose internal components of the computer  30 D such as the display  18 . In certain embodiments, a user of the computer  30 D may interact with the computer  30 D using various peripheral input devices, such as the input structures  22  or mouse  38 , which may connect to the computer  30 D via a wired and/or wireless I/O interface  24 . 
     Similarly,  FIG. 6  depicts a wearable electronic device  30 E representing another embodiment of the electronic device  10  of  FIG. 1  that may be configured to operate using the techniques described herein. By way of example, the wearable electronic device  30 E, which may include a wristband  43 , may be an Apple Watch® by Apple, Inc. However, in other embodiments, the wearable electronic device  30 E may include any wearable electronic device such as, for example, a wearable exercise monitoring device (e.g., pedometer, accelerometer, heart rate monitor), or other device by another manufacturer. The display  18  of the wearable electronic device  30 E may include a touch screen, which may allow users to interact with a user interface of the wearable electronic device  30 E. 
     The display  18  for the electronic device  10  may include a matrix of pixels that contain light emitting circuitry. Accordingly,  FIG. 7  illustrates a circuit diagram including a portion of a matrix of pixels of the display  18 . As illustrated, the display  18  may include a display panel  60 . Moreover, the display panel  60  may include multiple unit pixels  62  (here, six unit pixels  62 A,  62 B,  62 C,  62 D,  62 E, and  62 F are shown) arranged as an array or matrix defining multiple rows and columns of the unit pixels  62  that collectively form a viewable region of the display  18  in which an image may be displayed. In such an array, each unit pixel  62  may be defined by the intersection of rows and columns, represented here by the illustrated gate lines  64  (also referred to as “scanning lines”) and data lines  66  (also referred to as “source lines”), respectively. Additionally, power supply lines  68  may provide power to each of the unit pixels  62 . 
     Although only six unit pixels  62 , referred to individually by reference numbers  62   a - 62   f , respectively, are shown, it should be understood that in an actual implementation, each data line  66  and gate line  64  may include hundreds or even thousands of such unit pixels  62 . By way of example, in a color display panel  60  having a display resolution of 1024×768, each data line  66 , which may define a column of the pixel array, may include 768 unit pixels, while each gate line  64 , which may define a row of the pixel array, may include 1024 groups of unit pixels with each group including a red, blue, and green pixel, thus totaling 3072 unit pixels per gate line  64 . By way of further example, the panel  60  may have a resolution of 480×320 or 960×640. In the presently illustrated example, the unit pixels  62  may represent a group of pixels having a red pixel ( 62 A), a blue pixel ( 62 B), and a green pixel ( 62 C). The group of unit pixels  62 E,  62 E, and  62 F may be arranged in a similar manner. Additionally, in the industry, it is also common for the term “pixel” may refer to a group of adjacent different-colored pixels (e.g., a red pixel, blue pixel, and green pixel), with each of the individual colored pixels in the group being referred to as a “sub-pixel.” 
     The display  18  also includes a source driver integrated circuit (IC)  90 , which may include a chip, such as a processor or ASIC, configured to control various aspects of the display  18  and panel  60 . For example, the source driver IC  90  may receive image data  92  from the processor core complex  12  and send corresponding image signals to the unit pixels  62  of the panel  60 . The source driver IC  90  may also be coupled to a gate driver IC  94 , which may be configured to provide/remove gate activation signals to activate/deactivate rows of unit pixels  62  via the gate lines  64 . The source driver IC  90  may include a timing controller that determines and sends timing information/image signals  96  to the gate driver IC  94  to facilitate activation and deactivation of individual rows of unit pixels  62 . In other embodiments, timing information may be provided to the gate driver IC  94  in some other manner (e.g., using a timing controller that is separate from the source driver IC  90 ). Further, while  FIG. 7  depicts only a single source driver IC  90 , it should be appreciated that other embodiments may utilize multiple source driver ICs  90  to provide timing information/image signals  96  to the unit pixels  62 . For example, additional embodiments may include multiple source driver ICs  90  disposed along one or more edges of the panel  60 , with each source driver IC  90  being configured to control a subset of the data lines  66  and/or gate lines  64 . 
     In operation, the source driver IC  90  receives image data  92  from the processor core complex  12  or a discrete display controller and, based on the received data, outputs signals to control the unit pixels  62 . When the unit pixels  62  are controlled by the source driver IC  90 , circuitry within the unit pixels  62  may complete a circuit between a power source  98  and light elements of the unit pixels  62 . Additionally, to measure operating parameters of the display  18 , measurement circuitry  100  may be positioned within the source driver IC  90  to read various voltage and current characteristics of the display  18 , as discussed in detail below. 
     The measurements from the measurement circuitry  100  (or other information) may be used to determine offset data for individual pixels (e.g.,  62 A-F). The offset data may represent non-uniformity between the pixels, such as: neighboring pixels that have similar data, but different luminance, color non-uniformity between neighboring pixels, pixel row inconsistencies, pixel column inconsistencies, etc. Further, the offset data may be applied to the data controlling the pixels (e.g.,  62 A-F), resulting in compensated pixel data that may effectively remove these inconsistencies. 
     With this in mind,  FIG. 8  illustrates a block diagram of a process  150  for external compensation of pixels  62  and subsequent processing  151  at the display  18 , in accordance with an embodiment. Circuitry such as a system on chip (SOC)  152  may be used for pre-processing of pixel data, prior to the data reaching the display panel  60 . The pixel data in the SOC  152  is in the digital processing domain. On the SOC  152  side, offset data  154 , representing the non-uniformity or mismatch between the pixels  62 , is added  155  to the gray level data  156  (voltage values) of the pixels, which are determined using N byte input data  158 . This addition of offset data  154  to the gray level data  156 , results in N+M byte offset gray level data for each pixel. The offset gray level data is mapped to the gamma domain, as illustrated in block  159 . This process  150  is implemented for each pixel  62  of the display panel  60 . The mapped offset gray level data  160  for each pixel  62  (e.g., the externally compensated data for each pixel  62 ) is then provided  161  to the display panel  60 . 
     The display panel  60  may then perform the display panel  60  processing  151 . First, the display panel  60  may perform a linear digital-to-analog conversion, converting the data  160  from gray level data (G) to voltage (v)  162  (e.g., via a Gamma DAC  163 ), as illustrated by block  164 . The voltage  162  may be applied to the driving TFT  165 , resulting in a current (I)  166 , as illustrated by block  168 . The current  166  is then applied to a diode of the pixel  62 , resulting in outputted light or luminance (Lv)  170  at a diode  171  of the pixel  62 , as illustrated by block  172 . 
     The transformations in the SOC  152  may be complex, and could result in additional errors at times. These errors may contribute to non-uniformity of the pixels  62 , such as color-mismatching, etc. Further, the increase in input data size (e.g., N+M byte data), may result in an interface that uses higher bandwidth, and thus, uses more power, as well as increased precision to be handled by the DAC  163 . 
     In some embodiments, it may be beneficial to apply offset information for the pixel compensation in the driver integrated circuit.  FIG. 9  illustrates such an embodiment of circuitry  200 , where the offset data is applied in the driver integrated circuit, rather than in the SOC  152  or in the pixel  62 . As mentioned above, in the embodiment of  FIG. 8 , the SOC  152  is modified to allow the offset data  154  to be added  155  to the gray level data  156 . Further, because the embodiment of  FIG. 8  performs processing in the digital domain, a linear DAC is used to convert the digital gray level data  160  to voltage. In other words, the nonlinear data is mapped to linear data and then back to nonlinear data. Accordingly, the embodiment of  FIG. 9 , which implements the offset data  154  addition in the driver IC  94 , may be beneficial, in that the display pipeline architecture may not be affected by the external compensation. For example, the SOC  152  and pixel  62  may remain untouched. Further, as illustrated in  FIG. 9 , two parallel interfaces may send the pixel  62  data  158  and the offset data  154 , per pixel  62 , resulting in increased processing speed. 
     To perform the external compensation, circuitry is added to perform the driver IC  94  external compensation operations provided in the dashed box  204 . As illustrated in  FIG. 9 , the data  158  for each pixel  62  is provided to a nonlinear gamma DAC  205 . Serially or in parallel, the offset data  154  for each pixel  62  is provided to a linear offset DAC  206  of the driver IC  94 . The digital-to-analog conversion results in analog offset information (Vth information)  208 . The Vth information  208  is added via an addition  210  function to the outputted voltage of the DAC  205  in the driver IC  94 . The compensated voltage is passed from the addition  210  function, to the pixel  62 , where the voltage is applied to the driving TFT  165 , resulting in a current  166  (block  168 ). The current  166  is applied to the diode  171 , resulting in light or luminance (Lv)  170  emitted by the diode  171 . 
     The processing of  FIG. 9  may be completed in either the current domain or the voltage domain.  FIG. 10  illustrates circuitry  230  to implement the processing of  FIG. 9  in the current domain. In the circuitry  230  of  FIG. 10 , each of the processing steps and circuitry components is similar to those of  FIG. 9 , except that the nonlinear gamma DAC  205 ′ and the linear offset DAC  206 ′ are in a current mode. Further, because the driving TFT  165  works with voltage, current to voltage (I2V) conversion circuitry  232  may convert the compensated current to voltage, such that voltage is provided to the TFT  165 . In some embodiments, the current to voltage conversion may occur on each of the DAC  205  and  206  outputs, prior to the addition  210 . 
     Turning now to the voltage domain implementation, there are a number of techniques that may be implemented to offset the voltage data in the driver IC. In one embodiment, operational amplifiers (OPAMPS) may be used to add the voltage outputs of the two DACs  205  and  206 . However, this approach may utilize more power and circuit area, as additional amplifiers per pixel  62  may be used. 
     Alternatively or additionally, in some embodiments the offset DAC  206  may be embedded in the source driver IC  90 . As mentioned above, the source driver IC  90  drives each of the columns of pixels  62 .  FIGS. 11 and 12  illustrate embodiments where the offset DAC  206  is embedded in the source driver IC  90 . As illustrated in the circuitry  250  of  FIG. 11 , the gamma DAC  205  may provide the input voltage (Vin) for the source driver IC  90 . Further, the offset DAC  206 ′ and a resistor  252  are electrically coupled to the feedback path  254  of the source driver IC  90 . The resistor  252  may utilize a programmable resistance value that is defined by the voltage offset (VOFFSET). Using this configuration, the summation of the Offset DAC  206 ′ and the gamma DAC  205  may be provided, along with the current-to-voltage conversion (I2V), as illustrated by block  256 . 
       FIG. 12  illustrates circuitry  270  that implements the embedded offset DAC  206 ′ technique of  FIG. 11 , with a segmented current provided to the source driver IC  90  feedback path  254 , for fine-tuning. As illustrated, current outputs  272  and  274  are segmented and separated coupled to the feedback path  254 . Corresponding resistors  252 ′ and  252 ″ are used for the respective segmented current outputs  272  and  274 . While the current embodiment illustrates two segmented current outputs  272  and  274 , any number of current segments may be used, depending on fine-tuning needs. 
     In some embodiments, the gamma DAC  205  and the offset DAC  206  both provide voltages.  FIG. 13  illustrates circuitry for adding the gamma DAC  205  and the offset DAC  206 , in accordance with an embodiment. As illustrated in  FIG. 13 , the voltage of the gamma DAC  205  is halved and provided as an input voltage (Vin½) to the source driver IC  90 . A resistor  302  is applied to the offset DAC  206  and a resistor  304  is applied to the feedback path  254  of the source driver IC  90 . The offset DAC  206  with the applied resistor  302  is embedded in the feedback  254  after the resistor  304 . Using this configuration, the output  306  is the offset DAC  206  output added to the gamma DAC  205  output. 
     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: 20160920
Publication Date: 20181009
Grant Date: 20181009
Priority Date: 20160630
Inventors: VAHID FAR, MOHAMMAD B.
RICHMOND, Jesse A.
BI, YAFEI
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2320/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0242", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3208", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0242", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3258", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/3233", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/0295", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/027", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0295", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3291", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3225", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0828", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/027", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3266", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0285", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3275", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3291", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3225", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/006", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3275", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0285", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0295", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0828", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3266", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2310/027", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3258", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2300/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3291", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3208", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 58794201