PATENT DOCUMENT

Publication Number: US-12136394-B2
Application Number: US-202016802354-A
Country: US
Kind Code: B2

Title: Systems and methods for external off-time pixel sensing

Abstract:
An electronic device includes a display having multiple regions of pixels. Each pixel includes a diode that emits light based on an amount of current through the diode and a transistor that controls the amount of current flowing through the diode. The electronic device includes driver-integrated circuitry that reduces hysteresis in a first transistor of a first pixel of a region of pixels, settles a threshold voltage of the first transistor, applies a test voltage to the first transistor, and senses a current across the first transistor. The electronic device includes processing circuitry that determines a predetermined voltage based on the current and a predetermined current-voltage relationship determined at an initial temperature, determines a voltage difference between the test voltage and the predetermined voltage, and applies the predetermined voltage and the voltage difference to a second transistor of a second pixel of the region of pixels.

Claims:
What is claimed is: 
     
       1. An electronic display comprising:
 a pixel, wherein the pixel comprises:
 a diode configured to emit light based at least in part on an amount of current through the diode; and 
 a driver transistor configured to control the amount of current flowing through the diode based at least in part on a voltage applied to the driver transistor; 
 driver-integrated circuitry configured to, during a current sensing process associated with not displaying image content via the diode:
 send a hysteresis-reducing signal to the driver transistor; 
 send a threshold-settling signal to the driver transistor; 
 send a test voltage to the driver transistor without illuminating the diode, wherein the driver-integrated circuitry is configured to send the test voltage to the driver transistor without illuminating the diode by reducing a source voltage of the driver transistor, wherein the diode is directly electrically coupled to a drain of the driver transistor; and 
 sense a current across the driver transistor in response to the test voltage; 
 
 
 a plurality of display regions, wherein a first display region of the plurality of display regions comprises the pixel; and 
 a plurality of power planes configured to selectively supply independent supply voltages to the plurality of display regions, wherein a first power plane of the plurality of power planes is configured to supply a first supply voltage of the independent supply voltages to the first display region during the current sensing process, and wherein a second power plane of the plurality of power planes is configured to supply a second supply voltage of the independent supply voltages to a second display region, of the plurality of display regions, configured to display the image content while the first display region undergoes the current sensing process. 
 
     
     
       2. The electronic display of  claim 1 , communicatively coupled to processing circuitry separate from the electronic display, wherein the processing circuitry is configured to adjust image data configured to be sent to the pixel to compensate for operational variations of the electronic display based at least in part on the current sensed across the driver transistor. 
     
     
       3. The electronic display of  claim 2 , wherein the processing circuitry is configured to adjust the image data at least in part by:
 determining a certain voltage based at least in part on the current and a predetermined current-voltage relationship determined at an initial temperature; 
 determining a voltage difference between the test voltage and the certain voltage; and 
 applying a sum of the certain voltage and the voltage difference to the driver transistor. 
 
     
     
       4. The electronic display of  claim 2 , wherein the electronic display comprises a plurality of regions of pixels, wherein a region of pixels of the plurality of regions of pixels comprises the pixel, wherein the processing circuitry is configured to adjust the image data at least in part by:
 determining a certain voltage based at least in part on the current and a predetermined current-voltage relationship determined at an initial temperature; 
 determining a voltage difference between the test voltage and the certain voltage; and 
 applying a sum of the certain voltage and the voltage difference to a second driver transistor of a second pixel of the region of pixels. 
 
     
     
       5. The electronic display of  claim 1 , wherein the driver-integrated circuitry is configured to send the hysteresis-reducing signal, send the threshold-settling signal, and sense the current during an off-time of the electronic display. 
     
     
       6. The electronic display of  claim 1 , wherein the hysteresis-reducing signal is configured to alternate between a higher voltage value and a lower voltage value. 
     
     
       7. The electronic display of  claim 1 , wherein the threshold-settling signal comprises a settling voltage, wherein the threshold-settling signal is configured to settle a threshold voltage of the driver transistor to the settling voltage. 
     
     
       8. A method comprising:
 determining whether a usage time since a previous current sensing process of a display of an electronic device has exceeded a compensation time threshold; 
 determining whether a current time is indicative of a lack of use of the electronic device in response to determining that the usage time has exceeded the compensation time threshold; 
 determining whether the electronic device is charging or a battery of the electronic device has sufficient charge; and 
 in response to determining that the current time is indicative of the lack of use of the electronic device and that the electronic device is charging or the battery of the electronic device has sufficient charge, performing a current sensing process, wherein the current sensing process comprises:
 sending a hysteresis-reducing signal to a transistor of pixel driving circuitry configured to provide power to a diode of the display; 
 sending a test voltage to the transistor; and 
 sensing current in response to the test voltage. 
 
 
     
     
       9. The method of  claim 8 , comprising determining whether the usage time has exceeded a second compensation time threshold, less than the compensation time threshold, wherein the compensation time threshold is associated with a higher urgency to initiate the current sensing process than the second compensation time threshold. 
     
     
       10. The method of  claim 8 , comprising determining whether the current time is nighttime in response to determining that the usage time has exceeded the compensation time threshold, wherein determining whether the current time is indicative of the lack of use of the electronic device occurs in response to determining that the current time is nighttime in response to determining that the usage time has exceeded the compensation time threshold. 
     
     
       11. The method of  claim 8 , comprising determining whether a temperature at the display is sufficiently stable in response to determining that the electronic device is charging or the battery of the electronic device has sufficient charge, wherein sending the hysteresis-reducing signal to the transistor, sending the test voltage to the transistor, and sensing the current, occur in response to determining that the temperature at the electronic device is sufficiently stable. 
     
     
       12. The method of  claim 8 , comprising:
 determining a predetermined current-voltage relationship of a pixel of the display at initial conditions, the pixel comprising the diode; 
 determining a certain voltage corresponding to the current based at least in part on the predetermined current-voltage relationship; 
 determining a voltage difference between the certain voltage and the test voltage; and 
 storing the voltage difference in a lookup table. 
 
     
     
       13. The method of  claim 12 , comprising:
 determining a gamma voltage value configured to cause the diode of the pixel to emit light at a target luminance; and 
 determining a gain voltage value or an offset voltage value configured to adjust the gamma voltage value and cause the diode to emit the light of the target luminance. 
 
     
     
       14. The method of  claim 13 , comprising applying a sum of the voltage difference, the gamma voltage value, and the gain voltage value or the offset voltage value at the pixel to cause the diode of the pixel to emit the light of the target luminance. 
     
     
       15. The method of  claim 8 , comprising:
 determining whether the electronic device is about to be used or in use while sending the hysteresis-reducing signal to the transistor, sending the test voltage to the transistor, or sensing the current; and 
 interrupting sending the hysteresis-reducing signal to the transistor, sending the test voltage to the transistor, or sensing the current at the display, in response to determining that the electronic device is about to be used or in use. 
 
     
     
       16. The method of  claim 15 , wherein determining whether the electronic device is about to be used or in use comprises receiving sensor information from a movement sensor of the electronic device that the electronic device is being picked up or receiving an input signal from an input structure that the electronic device is being turned on. 
     
     
       17. The method of  claim 8 , wherein sending the test voltage to the transistor comprises sending the test voltage to the transistor without illuminating the diode. 
     
     
       18. An electronic device comprising:
 a display comprising:
 a plurality of regions of pixels, wherein a pixel of a region of pixels of the plurality of regions of pixels comprises:
 a diode configured to emit light associated with image content based at least in part on an amount of current through the diode; and 
 one or more transistors configured to control the amount of current flowing through the diode based at least in part on a data voltage associated with the image content; 
 
 driver-integrated circuitry configured to, during a current sensing period associated with not displaying the image content via the pixel:
 apply a hysteresis-reducing signal to a transistor of the one or more transistors; 
 apply a threshold-settling voltage to the transistor; 
 apply a test voltage to the transistor; and 
 sense a current across the transistor in response to the test voltage; and 
 
 a plurality of power planes, wherein each power plane is separately provided a plurality of supply voltages, wherein a first power plane of the plurality of power planes is configured to supply a first supply of power to the region of pixels of the plurality of regions of pixels, wherein a second power plane of the plurality of power planes is configured to supply a second supply of power, different from the first supply of power, to a second region of pixels of the plurality of regions of pixels and cause the image content to be displayed in the second region during the current sensing period of the pixel; and 
 
 processing circuitry communicatively coupled to the display, wherein the processing circuitry is configured to:
 determine a voltage compensation based at least in part on the current; and 
 during a display period associated with displaying the image content via the diode, generate the data voltage based at least in part on the voltage compensation. 
 
 
     
     
       19. The electronic device of  claim 18 , wherein the processing circuitry is configured to enable displaying of the image content, via the second power plane, on at least a portion of the display when the display is in a sleep mode. 
     
     
       20. The electronic device of  claim 18 , wherein the processing circuitry is configured to independently select respective operating modes for the plurality of power planes, wherein the first supply of power is associated with a first operating mode of the respective operating modes and the second supply of power is associated with a second operating mode of the respective operating modes.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/836,592 entitled “SYSTEMS AND METHODS FOR EXTERNAL OFF-TIME PIXEL SENSING,” filed Apr. 19, 2019, which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     SUMMARY 
     The present disclosure relates generally to electronic displays and, more particularly, to devices and methods for achieving improvements in sensing attributes of a light emitting diode (LED) electronic display or attributes affecting an LED electronic display. 
     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. 
     Flat panel displays, such as active matrix organic light emitting diode (AMOLED) displays, micro-LED (μLED) displays, and the like, are commonly used in 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 display panels typically provide a flat display in a relatively thin package that is suitable for use in a variety of electronic goods. In addition, such devices may 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. 
     LED displays typically include picture elements (e.g. pixels) arranged in a matrix to display an image that may be viewed by a user. Individual pixels of an LED display may generate light as a voltage is applied to each pixel. The voltage applied to a pixel of an LED display may be regulated by, for example, thin film transistors (TFTs). For example, a circuit-switching TFT may be used to regulate current flowing into a storage capacitor, and a driver TFT may be used to regulate the voltage being provided to the LED of an individual pixel. The growing reliance on electronic devices having LED displays has generated interest in improvement of the operation of the displays. 
     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. 
     The present disclosure relate to devices and methods for increased determination of the performance of certain electronic display devices including, for example, light emitting diode (LED) displays, such as organic light emitting diode (OLED) displays, active matrix organic light emitting diode (AMOLED) displays, or micro LED (μLED) displays. Under certain conditions, non-uniformity of a display induced by process non-uniformity temperature gradients, or other factors across the display should be compensated for to increase performance of a display (e.g., reduce visible anomalies). The non-uniformity of pixels in a display may vary between devices of the same type (e.g., two similar phones, tablets, wearable devices, or the like), vary over time and usage (e.g., due to aging and/or degradation of the pixels or other components of the display), and/or vary with respect to temperatures, as well as in response to additional factors. 
     To improve display panel uniformity, compensation techniques related to adaptive correction of the display may be employed. For example, as pixel response (e.g., luminance and/or color) can vary due to component processing, temperature, usage, aging, and the like, in one embodiment, to compensate for non-uniform pixel response, a property of the pixel (e.g., a current or a voltage) may be measured (e.g., sensed via a sensing operation) and compared to a target value that is, for example, stored in a lookup table or the like, to generate a correction value to be applied to correct pixel illuminations to match a desired gray level. In this manner, modified data values may be transmitted to the display to generate compensated image data (e.g., image data that accurately reflects the intended image to be displayed by adjusting for non-uniform pixel responses). 
     Various refinements of the features noted above may be made in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG.  1    is a schematic block diagram of an electronic device that performs display sensing and compensation, in accordance with an embodiment; 
         FIG.  2    is a perspective view of a notebook computer representing an embodiment of the electronic device of  FIG.  1   ; 
         FIG.  3    is a front view of a hand-held device representing another embodiment of the electronic device of  FIG.  1   ; 
         FIG.  4    is a front view of another hand-held device representing another embodiment of the electronic device of  FIG.  1   ; 
         FIG.  5    is a front view of a desktop computer representing another embodiment of the electronic device of  FIG.  1   ; 
         FIG.  6    is a front view and side view of a wearable electronic device representing another embodiment of the electronic device of  FIG.  1   ; 
         FIG.  7    is a block diagram of a system for display sensing and compensation of the electronic device of  FIG.  1   , according to an embodiment of the present disclosure; 
         FIG.  8    is a schematic diagram of the system for display sensing and compensation of  FIG.  7   , according to an embodiment of the present disclosure; 
         FIG.  9    is a circuit diagram of a display pixel of a display of the electronic device of  FIG.  1   , according to embodiments of the present disclosure; 
         FIG.  10    is a block diagram of predetermined lookup tables used to compensate for operational variations of the display of the electronic device of  FIG.  1   , according to embodiments of the present disclosure; 
         FIG.  11    is process for externally compensating for operational variations of the display of the electronic device of  FIG.  1   , according to embodiments of the present disclosure; 
         FIG.  12    is a timing diagram of data voltages applied to two pixels of the display of the electronic device of  FIG.  1    and resulting threshold voltages of the two pixels over time, according to embodiments of the present disclosure; 
         FIG.  13    is a timing diagram illustrating when data may be programmed and current may be sensed for pixels of the display of the electronic device of  FIG.  1   , according to embodiments of the present disclosure; 
         FIG.  14    is a schematic diagram of a first implementation of power rail architecture supporting an Always-On display of the electronic device of  FIG.  1   , according to embodiments of the present disclosure; 
         FIG.  15    is a schematic diagram of a second implementation of power rail architecture supporting an Always-On display of the electronic device of  FIG.  1   , according to embodiments of the present disclosure; 
         FIG.  16    is process for determining an appropriate time to sense and store voltage differences used to compensate for operational differences of the display of the electronic device of  FIG.  1   , according to embodiments of the present disclosure. 
     
    
    
     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. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, the phrase A “based on” B is intended to mean that A is at least partially based on B. Moreover, the term “or” is intended to be inclusive (e.g., logical OR) and not exclusive (e.g., logical XOR). In other words, the phrase A “or” B is intended to mean A, B, or both A and B. 
     Electronic displays are ubiquitous in modern electronic devices. As electronic displays gain ever-higher resolutions and dynamic range capabilities, image quality has increasingly grown in value. In general, electronic displays contain numerous picture elements, or “pixels,” that are programmed with image data. Each pixel emits a particular amount of light based on the image data. By programming different pixels with different image data, graphical content including images, videos, and text can be displayed. 
     Display panel sensing allows for operational properties of pixels of an electronic display to be identified to improve the performance of the electronic display. For example, variations in temperature and pixel aging (among other things) across the electronic display cause pixels in different locations on the display to behave differently. Indeed, the same image data programmed on different pixels of the display could appear to be different due to the variations in temperature and pixel aging. Without appropriate compensation, these variations could produce undesirable visual artifacts. However, compensation of these variations may hinge on proper sensing of differences in the images displayed on the pixels of the display. Accordingly, the techniques and systems described below may be utilized to enhance the compensation of operational variations across the display. 
     With this in mind, a block diagram of an electronic device  10  is shown in  FIG.  1   . As will be described in more detail below, the electronic device  10  may represent any suitable electronic device, such as a computer, a mobile phone, a portable media device, a tablet, a television, a virtual-reality headset, a vehicle dashboard, or the like. The electronic device  10  may represent, for example, a notebook computer  10 A as depicted in  FIG.  2   , a handheld device  10 B as depicted in  FIG.  3   , a handheld device  10 C as depicted in  FIG.  4   , a desktop computer  10 D as depicted in  FIG.  5   , a wearable electronic device  10 E as depicted in  FIG.  6   , or a similar device. 
     The electronic device  10  shown in  FIG.  1    may include, for example, a processor core complex  12 , a local memory  14 , a main memory storage device  16 , an electronic 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 machine-executable instructions stored on a tangible, non-transitory medium, such as the local memory  14  or the main memory storage device  16 ) 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 . Indeed, the various depicted components may be combined into fewer components or separated into additional components. For example, the local memory  14  and the main memory storage device  16  may be included in a single component. 
     The processor core complex  12  may carry out a variety of operations of the electronic device  10 , such as causing the electronic display  18  to perform display panel sensing and using the feedback to adjust image data for display on the electronic display  18 . The processor core complex  12  may include any suitable data processing circuitry to perform these operations, such as one or more microprocessors, one or more application specific processors (ASICs), or one or more programmable logic devices (PLDs). In some cases, the processor core complex  12  may execute programs or instructions (e.g., an operating system or application program) stored on a suitable article of manufacture, such as the local memory  14  and/or the main memory storage device  16 . In addition to instructions for the processor core complex  12 , the local memory  14  and/or the main memory storage device  16  may also store data to be processed by the processor core complex  12 . By way of example, the local memory  14  may include random access memory (RAM) and the main memory storage device  16  may include read only memory (ROM), rewritable non-volatile memory such as flash memory, hard drives, optical discs, or the like. 
     The electronic display  18  may display image frames, such as a graphical user interface (GUI) for an operating system or an application interface, still images, or video content. The processor core complex  12  may supply at least some of the image frames. The electronic display  18  may be a self-emissive display, such as an organic light emitting diodes (OLED) display, a micro-LED display, a micro-OLED type display, or a liquid crystal display (LCD) illuminated by a backlight. In some embodiments, the electronic display  18  may include a touch screen, which may allow users to interact with a user interface of the electronic device  10 . The electronic display  18  may employ display panel sensing to identify operational variations of the electronic display  18 . This may allow the processor core complex  12  to adjust image data that is sent to the electronic display  18  to compensate for these variations, thereby improving the quality of the image frames appearing on the electronic display  18 . 
     The input structures  22  of the electronic device  10  may enable a user to interact with the electronic device  10  (e.g., pressing a button to increase or decrease a volume level). The I/O interface  24  may enable electronic device  10  to interface with various other electronic devices, as may the network interface  26 . The network interface  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 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., ADSL, VDSL), digital video broadcasting-terrestrial (DVB-T) and its extension DVB Handheld (DVB-H), ultra wideband (UWB), alternating current (AC) power lines, and so forth. The power source  28  may include any suitable source of power, such as a rechargeable lithium polymer (Li-poly) battery and/or an alternating current (AC) power converter. 
     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  10 A, is illustrated in  FIG.  2    in accordance with one embodiment of the present disclosure. The depicted computer  10 A may include a housing or enclosure  36 , an electronic 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  10 A, such as to start, control, or operate a GUI or applications running on computer  10 A. For example, a keyboard and/or touchpad may allow a user to navigate a user interface or application interface displayed on the electronic display  18 . 
       FIG.  3    depicts a front view of a handheld device  10 B, which represents one embodiment of the electronic device  10 . The handheld device  10 B 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  10 B may be a model of an iPod® or iPhone® available from Apple Inc. of Cupertino, California. The handheld device  10 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 electronic display  18 . 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 serial bus (USB), or other similar connector and protocol. 
     User input structures  22 , in combination with the electronic display  18 , may allow a user to control the handheld device  10 B. For example, the input structures  22  may activate or deactivate the handheld device  10 B, navigate user interface to a home screen, a user-configurable application screen, and/or activate a voice-recognition feature of the handheld device  10 B. Other input structures  22  may provide volume control, or may toggle between vibrate and ring modes. The input structures  22  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  22  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  10 C, which represents another embodiment of the electronic device  10 . The handheld device  10 C may represent, for example, a tablet computer or portable computing device. By way of example, the handheld device  10 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, California. 
     Turning to  FIG.  5   , a computer  10 D may represent another embodiment of the electronic device  10  of  FIG.  1   . The computer  10 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  10 D may be an iMac®, a MacBook®, or other similar device by Apple Inc. It should be noted that the computer  10 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  10 D such as the electronic display  18 . In certain embodiments, a user of the computer  10 D may interact with the computer  10 D using various peripheral input devices, such as input structures  22 A or  22 B (e.g., keyboard and mouse), which may connect to the computer  10 D. 
     Similarly,  FIG.  6    depicts a wearable electronic device  10 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  10 E, which may include a wristband  43 , may be an Apple Watch® by Apple Inc. However, in other embodiments, the wearable electronic device  10 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 electronic display  18  of the wearable electronic device  10 E may include a touch screen display  18  (e.g., LCD, OLED display, active-matrix organic light emitting diode (AMOLED) display, and so forth), as well as input structures  22 , which may allow users to interact with a user interface of the wearable electronic device  10 E. 
       FIG.  7    is a block diagram of a system  50  for display sensing and compensation of the electronic device  10  of  FIG.  1   , according to an embodiment of the present disclosure. The system  50  includes the processor core complex  12 , which includes image correction circuitry  52 . The image correction circuitry  52  may receive image data  54 , and compensate for non-uniformity of the display  18  based on and induced by process non-uniformity temperature gradients, aging of the display  18 , and/or other factors across the display  18  to increase performance of the display  18  (e.g., by reducing visible anomalies). The non-uniformity of pixels in the display  18  may vary between devices of the same type (e.g., two similar phones, tablets, wearable devices, or the like), over time and usage (e.g., due to aging and/or degradation of the pixels or other components of the display  18 ), and/or with respect to temperatures, as well as in response to additional factors. 
     As illustrated, the system  50  includes aging/temperature determination circuitry  56  that may determine or facilitate determining the non-uniformity of the pixels in the display  18  due to, for example, aging and/or degradation of the pixels or other components of the display  18 . The aging/temperature determination circuitry  56  that may also determine or facilitate determining the non-uniformity of the pixels in the display  18  due to, for example, temperature. The variation in temperature may be due to changes in ambient temperature and/or a proximity of the pixels to a heat source (e.g., a fingertip of a user). In some cases, the pixels may be lay on top of or be in otherwise close proximity to other components of an electronic device that may be more densely packed with components due to the relatively small size of the electronic device (e.g., handheld, mobile, or portable electronic devices such as  10 B,  10 C,  10 E). As such, the variation in temperature may be due to operation of the components that the pixels are laying on top of or are in close proximity to. 
     The image correction circuitry  52  may send the image data  54  (for which the non-uniformity of the pixels in the display  18  have or have not been compensated for by the image correction circuitry  52 ) to analog-to-digital converter  58  of a driver-integrated circuit  60  of the display  18 . The analog-to-digital conversion converter  58  may digitize then image data  54  when it is in an analog format. The driver-integrated circuit  60  may send signals across gate lines to cause a row of pixels of a display panel  62 , including pixel  64 , to become activated and programmable, at which point the driver-integrated circuit  60  may transmit the image data  54  across data lines to program the pixels, including the pixel  64 , to display a particular gray level (e.g., individual pixel brightness). By supplying different pixels of different colors with the image data  54  to display different gray levels, full-color images may be programmed into the pixels. The driver-integrated circuit  60  may also include a sensing analog front end (AFE)  66  to perform analog sensing of the response of the pixels to data input (e.g., the image data  54 ) to the pixels. 
     The processor core complex  12  may also send sense control signals  68  to cause the display  18  to perform display panel sensing. In response, the display  18  may send display sense feedback  70  that represents digital information relating to the operational variations of the display  18 . The display sense feedback  70  may be input to the aging/temperature determination circuitry  56 , and take any suitable form. Output of the aging/temperature determination circuitry  56  may take any suitable form and be converted by the image correction circuitry  52  into a compensation value that, when applied to the image data  54 , appropriately compensates for non-uniformity of the display  18 . This may result in greater fidelity of the image data  54 , reducing or eliminating visual artifacts that would otherwise occur due to the operational variations of the display  18 . In some embodiments, the processor core complex  12  may be part of the driver-integrated circuit  60 , and as such, be part of the display  18 . 
       FIG.  8    is a schematic diagram of the system  50  for display sensing and compensation of  FIG.  7   , according to an embodiment of the present disclosure. The processor core complex  12  may include image data generation and processing circuitry  80  to generate the image data  54  for display by the electronic display  18 . The image data generation and processing circuitry  80  represents various circuitry and processing that may be employed by the processor core complex  12  to generate the image data  54  and control the electronic display  18 . As such, the image data generation and processing circuitry  80  may include, for example, the image correction circuitry  52  and/or the aging/temperature determination circuitry  56  of  FIG.  7   . In some embodiments, the image data generation and processing circuitry  80  may include a graphics processing unit, a display pipeline, or the like, to facilitate control of operation of the electronic display  18 . The image data generation and processing circuitry  80  may include a processor and memory such that the processor of the image data generation and processing circuitry  80  may execute instructions and/or process data stored in memory of the image data generation and processing circuitry  80  to control operation of the electronic display  18 . 
     To compensate for operational variations of the electronic display  18  due to, for example, temperature variation or aging of the display  18 , the processor core complex  12  may provide sense control signals  82  to cause the electronic display  18  to perform display panel sensing and generate display sense feedback  84 . The display sense feedback  84  represents digital information relating to the operational variations of the electronic display  18 . The display sense feedback  84  may take any suitable form, and may be converted by the image data generation and processing circuitry  80  into a compensation value that, when applied to the image data  54 , appropriately compensates for the conditions of the electronic display  18  in the image data  54 . This may result in greater fidelity of the image data  54 , reducing or eliminating visual artifacts that would otherwise occur due to the operational variations of the electronic display  18 . 
     The electronic display  18  includes an active area  86  with an array of pixels  64 . The pixels  64  are schematically shown distributed substantially equally apart and of the same size, but in an actual implementation, pixels of different colors may have different spatial relationships to one another and may have different sizes. In one example, each pixel  64  may have a red-green-blue (RGB) format that includes red, green, and blue pixels or sub-pixels. In another example, the pixels  64  may take a red-green-blue-green (RGBG) format in a diamond pattern. The pixels  64  are controlled by the driver-integrated circuit  60 , which may be a single module or may be made up of separate modules, such as a column or source driver-integrated circuit  88  and a row or gate driver-integrated circuit  90 . The driver-integrated circuit  60  (e.g., the row driver-integrated circuit  90 ) may send signals across gate lines  92  (e.g., using gate drivers) to cause a row of pixels  64  to become activated and programmable, at which point the driver-integrated circuit  60  (e.g., the column driver-integrated circuit  88 ) may transmit image data signals across data lines  94  to program the pixels  64  to display a particular gray level (e.g., individual pixel brightness). By supplying different pixels  64  of different colors with image data  54  to display different gray levels, full-color images may be programmed into the pixels  64 . The image data  54  may be driven to an active row of pixels  64  via source drivers  96 , which may also be referred to as column drivers. 
     Regardless of the particular arrangement and layout of the pixels  64 , each pixel  64  may be sensitive to changes on the active area  86  of the electronic display  18 , such as variations and temperature of the active area  86 , as well as the overall age of the pixel  64 . Indeed, when each pixel  64  is a light emitting diode (LED), it may gradually emit less light over time. This effect is referred to as aging, and takes place over a slower time period than the effect of temperature on the pixel  64  of the electronic display  18 . 
     As described above, the electronic display  18  may display image frames through control of the luminance of the pixels  64  based on the received image data  54 . When a pixel  64  is activated (e.g., via a gate activation signal across a gate line  92  activating a row of pixels  64 ), luminance of a display pixel  64  may be adjusted by image data  54  received via a data line  94  coupled to the pixel  64 . Thus, as depicted, each pixel  64  may be located at an intersection of a gate line  92  (e.g., which may act as, include, or be disposed alongside a scan line) and a data line  94  (e.g., a source line). Based on the received image data  54 , the luminance of a display pixel  64  may be adjusted using electrical power supplied from a power source  28 , for example, via power a supply lines coupled to the pixel  64 . 
     In some embodiments, to facilitate displaying an image frame, a timing controller may determine and transmit timing data to a gate driver of the row driver-integrated circuit  90  based on the image data  54 . For example, in the depicted embodiment, the timing controller may be included in the column driver-integrated circuit  88 . The column driver-integrated circuit  88  may receive image data  54  that indicates desired luminance of one or more display pixels  64  for displaying an image frame of the image data  54 , analyze the image data  54  to determine the timing data based on the display pixels  64  that the image data  54  corresponds to, and transmit the timing data to the gate driver of the row driver-integrated circuit  90 . Based on the timing data, the gate driver may then transmit gate activation signals to activate a row of display pixels  64  via a gate line  92 . 
     As illustrated, the image data generation and processing circuitry  80  may be externally coupled to the electronic display  18 . That is, the image data generation and processing circuitry  80  may be included in the processor core complex  12 , which is separate from but communicatively coupled to the electronic display  18  and the driver-integrated circuit  60  (including the column driver-integrated circuit  88  and the row driver-integrated circuit  90 ) of the electronic display  18 . Advantageously, the image data generation and processing circuitry  80  may be modular from the display  18  and conveniently updated and/or replaced (e.g., compared to if it were integrated in the display  18 ). Moreover, in cases where the system  50  is part of a component-dense electronic device  10  (such as the handheld devices  10 B-C or the wearable electronic device  10 E) that would place a display-integrated image data generation and processing circuitry in close proximity to (e.g., underlying) the pixels  64 , heat generated from the image data generation and processing circuitry  80  may combine or intermix with the heat generated from the pixels  64 , which may result in inaccurate temperature measurements of the pixels  64 . However, in other embodiments, the image data generation and processing circuitry  80  may be part of the display  18 . 
     Display panel sensing may be used to obtain the display sense feedback  84 , which may enable the processor core complex  12  to generate compensated image data  54  to negate the effects of temperature, aging, and other variations of the active area  86 . The driver-integrated circuit  60  (e.g., the column driver-integrated circuit  89 ) may include the sensing analog front end (AFE)  66  to perform analog sensing of the response of pixels  64  to test data (e.g., test image data) or user data (e.g., user image data). It should be understood that further references to test data or test image data in the present disclosure include test data and/or user data. The analog signal may be digitized by sensing analog-to-digital conversion circuitry (ADC)  58 . 
     For example, to perform display panel sensing, the electronic display  18  may program one of the pixels  64  with test data (e.g., having a particular reference voltage or reference current). The sensing analog front end  66  then senses (e.g., measures, receives, etc.) at least one value (e.g., voltage, current, etc.) along sense line  98  connected to the pixel  64  that is being tested. Here, the data lines  94  are shown to act as extensions of the sense lines  98  of the electronic display  18 . In other embodiments, however, the display active area  86  may include other dedicated sense lines  98  or other lines of the display  18  (e.g., such as the gate or scan lines  92 ) may be used as sense lines  98  instead of the data lines  94 . In some embodiments, other pixels  64  that have not been programmed with test data may be also sensed at the same time a pixel  64  that has been programmed with test data is sensed. Indeed, by sensing a reference signal on a sense line  98  when a pixel  64  on that sense line  98  has not been programmed with test data, a common-mode noise reference value may be obtained. This reference signal can be removed from the signal from the test pixel  64  that has been programmed with test data to reduce or eliminate common mode noise. 
     The analog signal may be digitized by the sensing analog-to-digital conversion circuitry  58 . The sensing analog front end  66  and the sensing analog-to-digital conversion circuitry  58  may operate, in effect, as a single unit. The driver-integrated circuit  60  (e.g., the column driver-integrated circuit  88 ) may also perform additional digital operations to generate the display sense feedback  84 , such as digital filtering, adding, or subtracting, to generate the display sense feedback  84 , or such processing may be performed by the processor core complex  12 . 
       FIG.  9    is a circuit diagram of a display pixel  64  of the electronic display  18  of the electronic device  10  of  FIG.  1   , according to embodiments of the present disclosure. Each pixel  64  may include a first circuit-switching thin-film transistor (TFT)  110 , a second circuit-switching TFT  112 , a storage capacitor  114 , a diode  116  (e.g., an OLED), and a driver TFT  118 . Each of the storage capacitor  114  and the diode  116  may be coupled to any suitable negative or ground power supply voltage, V SSEL    120 . That is, the negative power supply voltage, V SSEL    120  (which may be provided by a voltage rail in the display panel  62  and supplied by the driver-integrated circuit  60 ), may provide between 0 and, for example, −100 Volts (V), such as a voltage of zero, −1 V, −2 V, −4 V, −6 V, or any other suitable negative or ground voltage. While V SSEL    120  is referred to as a negative or ground power supply voltage, it should be understood this is with respect to the positive power supply voltage V DDEL    128 . As such, in some cases, V SSEL    120  may be positive, as long as it provides a voltage that is less than V DDEL    128 . For example, if V DDEL    128  is 4 V, then V SSEL    120  may be 2 V. Moreover, variations may be utilized in place of the illustrated pixel  64 . For example,  FIG.  9    illustrates the first circuit-switching TFT  110  and the driver TFT  118  as p-channel metal-oxide-semiconductor (PMOS) TFTs. However, in some embodiments, the first circuit-switching TFT  110  and/or the driver TFT  118  may be n-channel metal-oxide-semiconductor (NMOS) TFTs. Similarly,  FIG.  9    illustrates the second circuit-switching TFT  112  as an NMOS TFT, though, in some embodiments, the second circuit-switching TFT  112  may be a PMOS TFT. 
     To facilitate adjusting luminance and operating the diode  116 , the first circuit-switching TFT  110 , the second circuit-switching TFT  112 , and the driver TFT  118  may each serve as a switching device that may couple to or decouple from other circuits and be controllably turned on and off by voltage applied to their respective gates. In the depicted embodiment, the gate of the first circuit-switching TFT  110  is electrically coupled to a gate line  122 . Accordingly, when a gate activation signal (e.g., an emission voltage EM which may be provided by a voltage rail in the display panel  62  and supplied by the driver-integrated circuit  60 ) received from the gate line  122  is below a threshold voltage, the first circuit-switching TFT  110  may turn on, thereby activating the pixel  64  and charging the storage capacitor  114  with image data received at data line  124 . When the gate activation signal received from the gate line  122  is above the threshold voltage, the first circuit-switching TFT  110  may turn off, thereby deactivating the pixel  64  and ceasing charging of the storage capacitor  114  with the image data received at the data line  124 . The signal received by the driver TFT  118  from the data line  124  may be referred to as a V GS  signal, since it is received between the gate and the source of the driver TFT  118 . 
     Additionally, in the depicted embodiment, the gate of the driver TFT  118  is electrically coupled to the storage capacitor  114 . As such, voltage of the storage capacitor  114  may control operation of the driver TFT  118 . More specifically, in some embodiments, the driver TFT  118  may be operated in an active region to control magnitude of supply current flowing through the diode  116 , such as from a power supply providing positive supply voltage V DDEL    128 . That is, the positive power supply voltage, V DDEL    128  (which may be provided by a voltage rail in the display panel  62  and supplied by the driver-integrated circuit  60 ), may provide between 0 and, for example, 100 V, such as a voltage of zero, 1 V, 2 V, 4 V, 6 V, or any other suitable positive voltage (relative to the negative or ground power supply voltage, V SSEL    120 ). In other words, as gate voltage (e.g., storage capacitor  114  voltage) increases above a threshold voltage, the driver TFT  118  may increase the amount of its channel available to conduct electrical current, thereby increasing supply current flowing to the diode  116 . On the other hand, as the gate voltage decreases while still being above the threshold voltage, the driver TFT  118  may decrease the amount of its channel available to conduct electrical current, thereby decreasing supply current flowing to the diode  116 . The luminance of the diode  116  is dependent on the amount of current flowing through the diode  116 . In this manner, the luminance of the pixel  64  may be controlled and, when similar techniques are applied across the display  18  (e.g., to the pixels  64  of the display  18 ), an image may be displayed. 
     As illustrated, the gate of the second circuit-switching TFT  112  is electrically coupled to a scan line  126 . Accordingly, when a gate activation signal (e.g., a scan voltage provided by a voltage rail in the display panel  62  and supplied by the driver-integrated circuit  60 ) received from the scan line  126  is above a threshold voltage, the second circuit-switching TFT  112  may be turned on to supply an initialization or suppression voltage V INI    130  to the storage capacitor  114  to assist in turning off the diode  116  when it is not in use or when it is deactivated. In particular, V INI    130  may be supplied to the storage capacitor  114  to reverse bias the diode  116 . As such, the initialization voltage V INI    130  may be any suitable voltage that assists in turning off the diode  116  and/or reverse biases the diode  116 , such as a negative voltage of between −1 V and, for example, −12 V, such as −1 V or −2 V. Supplying the initialization voltage V INI    130  to the storage capacitor  114  and thus the diode  116  may improve pixel response time and/or reduce lateral leakage current from the pixel  64 . When the gate activation signal received from the scan line  126  is below the threshold voltage, the second circuit-switching TFT  112  may turn off, thereby ceasing charging of the storage capacitor  114  with the initialization voltage V INI    130 . 
     However, an oxide TFT, such as the first circuit-switching TFT  110 , the second circuit-switching TFT  112 , and/or the driver TFT  118 , may undergo a threshold shift as the oxide TFT ages. That is, the threshold voltage of, for example, the second circuit-switching TFT  112 , that is compared to the gate activation signal received from the scan line  126  to determine whether to turn the second circuit-switching TFT  112  on or off, may shift or change, which may result in inaccurate and/or inconsistent threshold comparison results, possibly leading to undesirable image artifacts displayed by the pixel  64 . As such, to properly operate the oxide TFTs (e.g.,  110 ,  112 ,  118 ) and display image data using the pixel  64 , the processor core complex  12  may sense or receive these threshold shifts and compensate for them. 
     Moreover, the rate at which the oxide TFT ages may vary with or be dependent upon temperature. That is, a pixel  64  may age faster when experiencing a higher temperature when compared to a pixel  64  experiencing a lower temperature. And while it may be ideal to sense each pixel  64  of the display  18 , doing so may be unrealistic due to a lack of processing power and/or time. On the other hand, sensing a single pixel  64  that would be representative of the entire display  18  may be inaccurate, as temperature variations of gradients often are applied to a region or group of contiguous pixels  64  (e.g., in the case of a fingertip being the source of body heat to a group of pixels  64 , a component disposed underneath a group of pixels  64 , and so on). As such, sensing for a display  18  may be more realistically and/or accurately performed using a grid-based technique (e.g., for a region or group of contiguous pixels  64 ). That is, the pixels  64  of the display  18  may be grouped into regions. For each region of pixels  64  (e.g., a 4 pixel by 4 pixel (4×4 pixel) group, a 6×8 pixel group, a 8×10 pixel group, a 16×20 pixel group, or any other suitable size pixel group), a current may be sensed for a representative pixel  64 , which may capture an effect of aging on the representative pixel  64  and/or components (e.g., the TFTs  110 ,  112 ,  118 ) of the pixel  64 , that may apply to the region of pixels  64 . While the remainder of the present disclosure discusses sensing of the pixel  64  in terms of sensing current, it should be understood that the presently disclosure techniques may be similarly applied to sensing other operational characteristics of the pixel  64 , such as voltage. 
     As such, to compensate for operational variations, such as aging, for a region of pixels  64 , the processor core complex  12  may instruct the driver-integrated circuit  60  to apply a test voltage to a driver TFT  118  via a data line  124  of a representative pixel  64  of the region of pixels  64 , and sense the resulting current (e.g., across the driver TFT  118  or across the diode  116  of the pixel  64 ). A predetermined current-voltage relationship (determined at an initial temperature and age (e.g., initial conditions) of the pixel  64  (e.g., at a manufacturing facility of the display  18 ) may be stored in the local memory  14  and/or the main memory storage device  16 . Using the predetermined current-voltage relationship, the processor core complex  12  may determine a predetermined voltage that supplies the same resulting current (e.g., to the driver TFT  118  or the diode  116 ). The processor core complex  12  may then determine a voltage difference between the test voltage and the predetermined voltage for the region of pixels  64 . This voltage difference may compensate for operational variations (e.g., aging) of the pixels  64  in the region. The processor core complex  12  may store these voltage differences in a voltage difference lookup table or map (e.g., in the local memory  14  and/or the main memory storage device  16 ) to be applied when displaying image data  54 . That is, when it is desired for a diode  116  of a pixel  64  of the region of pixels  64  to emit light of a target luminance corresponding to the resulting current, the processor core complex  12  and/or the driver-integrated circuit  60  may apply a voltage equal to the sum of the predetermined voltage for that pixel  64  and the voltage difference, thereby compensating for operational variations (e.g., aging) of the pixel  64 . 
     Due to the length of time it may take to perform the sensing (e.g., for a number of pixels  64  of the display  18 ) and more controlled or stable conditions, the sensing may be performed while the display  18  is off (e.g., during “off-time” of the display  18 ). While “off-time” may include when the display  18  is unpowered (e.g., the electronic device  10  is turned off), “off-time may also include when the display  18  is powered but not actively being used. This may include such times as when the electronic device  10  is not being used by a user (e.g., for a threshold amount of time), when the electronic device  10  is charging (e.g., plugged in), at a time associated with a pattern of not being used (e.g., between 3 AM and 5 AM), and so on. When the sensing is being performed, it may be desirable that emission of light from the diode  116  is prevented (such that a user of the electronic device  10  may not notice that current sensing is being performed). With this in mind, the presently disclosed systems and methods may also support immediate exit from off-time sensing when there is an indication that image data should be displayed (e.g., the user picks up the electronic device  10  and starts using it). 
     Moreover, to operate at higher efficiency while providing these features, power provided to the pixel  64  via, for example, the driver-integrated circuit  60 , may be reduced. In particular, the voltage difference between the positive supply voltage, V DDEL    128 , and the negative power supply voltage, V SSEL    120 , provided to the pixel  64  may be minimized or reduced, such as by reducing it to 1 V. For example, the driver-integrated circuit  60  may provide 1 V to the voltage rail supplying the positive supply voltage, V DDEL    128 , to the pixel  64 , and provide 0 V to the voltage rail supplying the negative power supply voltage, V SSEL    120 , to the pixel  64 . Additionally, the emission voltage EM provided on the gate line  122  to the pixel  64  and the scan voltage provided by the scan line  126  may be minimized or reduced. For example, the driver-integrated circuit  60  may provide −1 V to the voltage rail supplying the emission voltage EM provided on the gate line  122  to the pixel  64 , and provide −1 V to the voltage rail supplying the scan voltage provided by the scan line  126 . 
     In some cases, a pixel  64  may inadvertently retain the image data most recently programmed in it (e.g., exhibiting hysteresis in, for example, the driver TFT  118 ). Because this hysteresis may result in inaccurate current sensing at the pixel  64 , the processor core complex  12  may cause the driver-integrated circuit  60  to reduce the hysteresis in components of the pixel  64  (such as the driver TFT  118 ) for more accurate current sensing and more effective compensation. As such, the driver-integrated circuit  60  may perform hysteresis reduction on the pixel  64  prior to sensing current at (the driver TFT  118  or the diode  116  of) the pixel  64  (and during off-time of the display  18 ). Moreover, after performing hysteresis reduction on the pixel  64 , the threshold voltage of the driver TFT  118  may have settled to a voltage that, if used to sense current from, may result in inaccurate current sensing. As such, the processor core complex  12  may cause the driver-integrated circuit  60  to settle the threshold voltage of the driver TFT  118  to a proper settling voltage prior to sensing current. While the remainder of the specification discusses settling the threshold of the driver TFT  118 , it should be understood that the driver-integrated circuit  60  may additionally or alternatively settle the threshold voltages of the circuit-switching TFTs  110 ,  112  to avoid threshold shifting and possible inaccurate current sensing. 
     In some embodiments, multiple predetermined lookup tables or maps may be determined at the initial conditions of the display  18  (e.g., at an initial temperature and age), and the processor core complex  12  may use the predetermined lookup tables or maps to determine the voltage difference map and/or apply the voltage difference map to compensate for present operational variations of the display  18 . For example,  FIG.  10    is a block diagram of predetermined lookup tables used to compensate for operational variations of the display  18  of the electronic device  10  of  FIG.  1   , according to embodiments of the present disclosure. 
     At an initial time period  135 , such as at the factory or manufacturing facility where the displays  18  are made or assembled, initial (e.g., T0) factory display non-uniformity calibration  136  may be performed. In particular, the initial factory display non-uniformity calibration  136  may be performed optically, such as by applying different test voltages to the driver TFTs  118  of the pixels  64  and capturing images of the pixels  64  while the respective diodes  116  are emitting the resulting different luminances. An initial gamma lookup table  137  may be generated from the initial factory display non-uniformity calibration  136  that stores gamma or brightness values of each diode  116  of each pixel  64  and gamma voltage values that cause the pixel  64  to emit the corresponding gamma values. An initial gain lookup table  138  may also be generated that stores gain voltage values to add to the gamma voltage values in the initial gamma lookup table  137  so that diodes  116  that were emitting dimmer luminances than desired may emit the proper luminances. Similarly, an initial offset lookup table  139  may be generated that stores offset voltage values to subtract from the gamma voltage values in the initial gamma lookup table  137  so that diodes  116  that were emitting brighter luminances than desired may emit the proper luminances. 
     Additionally, initial factory current sensing  140  may be performed. In particular, different test voltages may be applied to the driver TFTs  118  of the pixels  64  and current may be sensed at the driver TFTs  118  or the diodes  116 . The test voltages and currents may be stored in an initial current-voltage lookup table  141  (e.g., “I_TestGray @T0”). 
     During a current sensing period  142 , off-time current sensing  143  may be performed. In particular, the processor core complex  12  may cause the driver-integrated circuit  60  to perform hysteresis reduction, threshold voltage settling, and current sensing. The processor core complex  12  may store the test voltages applied and resulting sensed currents in a present current-voltage lookup table  144  (e.g., “I_TestGray @2months”). The processor core complex  12  may thus determine the voltage differences between voltages applied in the initial current-voltage lookup table  141  and the present current-voltage lookup table  144  (for each corresponding current), and store them in a voltage difference lookup table  145  (e.g., “ΔV aging ”). In some embodiments, the present current-voltage lookup table  144  may not include current and voltage values for each pixel  64 , but instead may include current and voltage values for each representative pixel  64  of a region of pixels  64  of the display  18 . As such, for each pixel  64  of each region of pixels  64 , the processor core complex  12  may determine a voltage difference between voltages applied in the initial current-voltage lookup table  141  associated with a respective pixel  64  and the present current-voltage lookup table  144  associated with a respective representative pixel  64  in the respective region of pixels  64  that includes the respective pixel  64  (for each corresponding current) to generate the voltage difference lookup table  145 . 
     During a display period  146 , the processor core complex  12  may receive the image data  54  to be displayed, the gamma lookup table  137 , the gain lookup table  138 , the offset lookup table  139 , and the voltage difference lookup table  145 . The processor core complex  12  may then display  147  the image data  54  by, for each pixel  64 , receiving or determining a target luminance value for the pixel  64  from the image data  54 , receiving or determining a gamma voltage value to apply at the driver TFT  118  of the pixel  64  to cause the diode  116  of the pixel  64  to emit light of the target luminance value as provided by the gamma lookup table  137 , receiving or determining a gain voltage value as provided by the gain lookup table  138  and/or receiving or determining an offset voltage value as provided by the offset lookup table  139  corresponding to the target luminance value (or the gamma voltage value), receiving or determining a voltage difference value from the voltage difference lookup table  145 , and applying the sum of the gamma voltage value, the gain voltage value or the offset voltage value, and the voltage difference value to the driver TFT  118  of the pixel  64 . In this manner, the processor core complex  12  may use the predetermined lookup tables to determine the voltage difference lookup table  145  and/or apply the voltage difference lookup table  145  to compensate for present operational variations of the display  18 . 
     With this in mind,  FIG.  11    is process  154  for externally compensating for operational variations (e.g., aging) of the display  18  of the electronic device  10  of  FIG.  1   , according to embodiments of the present disclosure. The process  154  may be repeated for multiple pixels  64  to determine multiple target voltages to be applied at respective driver TFTs  118  of the multiple pixels  64  to compensate for operational variations of each of the multiple pixels  64 . While the process  154  is described using steps in a specific sequence, it should be understood that the present disclosure contemplates that the describe steps may be performed in different sequences than the sequence illustrated, and certain described steps may be skipped or not performed altogether. In some embodiments, the process  154  may be implemented by executing instructions stored in a tangible, non-transitory, computer-readable medium, such as the local memory  14  and/or the main memory storage device  16 , using a processor, such as the processor core complex  12 , and, in particular, the image correction circuitry  52  and/or the aging/temperature determination circuitry  56  of the processor core complex  12  shown in  FIG.  7   . In alternative or additional embodiments, the process  154  may be implemented by the processor causing or instructing components of the display  18 , such as the driver-integrated circuit  60 , to carry out instructions. 
     As illustrated, in process block  155 , the processor core complex  12  causes the driver-integrated circuit  60  to send a hysteresis-reducing signal to the driver TFT  118  of a first pixel  64  in a region of pixels  64 . In particular, the driver-integrated circuit  60  may send the hysteresis-reducing signal to the data line  124  of the first pixel  64 . The hysteresis-reducing signal may be part of the image data  54  and/or the sense control signals  82  sent by the processor core complex  12 . In some embodiments, the hysteresis-reducing signal may be a fixed value (e.g., a fixed bias voltage level or value) while, in other embodiments, the hysteresis-reducing signal may be a waveform that has a voltage level or value that varies. Using a fixed value as the hysteresis-reducing signal may have power advantages for the electronic device  10  since, for example, one or more of the portions of the device, such as the processor core complex  12 , may shut down and/or may be placed into a sleep mode to save power while, for example, the driver-integrated circuit  60  may continue operation. 
       FIG.  12    is a timing diagram of data voltages applied to two pixels  64  of a display  18  of the electronic device  10  of  FIG.  1    and resulting threshold voltages of the two pixels  64  over time, according to embodiments of the present disclosure. A first portion of the timing diagram illustrates the hysteresis reduction process  160  performed by the processor core complex  12  and/or the driver-integrated circuit  60  in process block  155 . In particular, the driver-integrated circuit  60  may apply the hysteresis-reducing signal  162  (illustrated in the form of a waveform) as data voltages  164 ,  166  to the sources of the driver TFTs  118  of the two pixels  64  via respective data lines  124 . The hysteresis-reducing signal  162  alternates between a high voltage value  168  and a low voltage value  170  to reduce or rid the driver TFTs  118  of the previous charge or image data recently programmed in the driver TFTs  118 . The high voltage value  168  and the low voltage value  170  may be any suitable voltage values that enable the driver TFTs  118  to settle quickly and thus reduce hysteresis, such as, respectively, 1 V and 0 V, 2 V and 0 V, 1 V and −1 V, and so on. The hysteresis reduction process  160  may be performed in any suitable amount of time, such as between 30 seconds and 10 minutes, including 4 minutes, 5 minutes, 6 minutes, and so on. 
     Prior to applying the hysteresis-reducing signal  162 , the threshold voltages  172 ,  174  of the driver TFTs  118  of the two pixels  64  may not be the same, and may not have settled to a settling voltage  176 , which may cause inaccurate current sensing. As illustrated, after applying the hysteresis-reducing signal  162 , at time  178 , the threshold voltages  172 ,  174  of the driver TFTs  118  have quickly settled and are approximately the same. That is, without applying the hysteresis-reducing signal  162 , the threshold voltages  172 ,  174  of the driver TFTs  118  may have settled, but taken more time to settle. However, as illustrated, at time  178 , the threshold voltages  172 ,  174  of the driver TFTs  118  have settled to a voltage  180  different from the settling voltage  176 , which may be cause inaccurate current sensing. 
     Turning back to  FIG.  11   , in process block  156 , the processor core complex  12  causes the driver-integrated circuit  60  to send a settling voltage signal (e.g., to cause the settling voltage  176  to be supplied) to the driver TFT  118  of the first pixel  64 . In particular, the settling voltage signal may supply the settling voltage  176  at the data line  124  of the first pixel  64 . The settling voltage  176  may be any suitable voltage that may result in accurate current sensing. In some embodiments, the settling voltage may correspond to a luminance, brightness, or grey level or value of the first pixel  64 . For example, current sensing may be accurate when the voltage supplied to the source of the driver TFT  118  from the data line  124  and/or the threshold voltage of the driver TFT  118  corresponds to a grey level of 31. As illustrated in  FIG.  12   , a second portion f the timing diagram illustrates the settling voltage process  182  of applying the settling voltage  184  to the sources of the driver TFTs  118  of the two pixels  64  from respective data lines  124 . The settling voltage process  182  may be performed in any suitable amount of time, such as between 10 seconds and 10 minutes, including 90 seconds, 120 seconds, 150 seconds, and so on. As a result, the threshold voltages  172 ,  174  of the driver TFTs  118  have settled to the settling voltage  176 , where current sensing may produce accurate results. 
     Turning back to  FIG.  11   , in process block  157 , the processor core complex  12  causes the driver-integrated circuit  60  to sense a current of the first pixel  64  by applying a test voltage to the driver TFT  118  of the first pixel  64 . In particular, the driver-integrated circuit  60  senses the current after reducing hysteresis in the driver TFT  118  (from process block  155 ) and applying the settling voltage  184  (from process block  156 ) to ensure accurate current sensing. The processor core complex  12  may cause driver-integrated circuit  60  to apply the test voltage to the driver TFT  118  via the data line  124 , and sense the current across the driver TFT  118  or the diode  116 . A third portion of the timing diagram of  FIG.  12    illustrates the current sensing process  186  during which the driver-integrated circuit  60  may apply the test voltage and sense the current across the driver TFT  118  for accurate results. The current sensing process  186  may be performed in any suitable amount of time, such as between 10 seconds and 10 minutes, including 90 seconds, 120 seconds, 150 seconds, and so on. 
     Turning back to  FIG.  11   , in process block  158 , the processor core complex  12  determines a voltage difference between the test voltage and a predetermined voltage of the first pixel  64  corresponding to the current. In particular, a predetermined current-voltage relationship (determined at an initial temperature and age (e.g., initial conditions) of the pixel  64  (e.g., at a manufacturing facility of the display  18 ) may be stored in the local memory  14  and/or the main memory storage device  16 . Using the predetermined current-voltage relationship, the processor core complex  12  may determine a predetermined voltage that supplies the current at (e.g., the driver TFT  118  or the diode  116  of) the first pixel  64 . The processor core complex  12  may then subtract the predetermined voltage from the test voltage to determine the voltage difference. This voltage difference may compensate for operational variations (e.g., aging) of, not only the pixel  64 , but also pixels  64  in a region including the pixel  64 . The processor core complex  12  may store the voltage difference in a lookup table or map of voltage differences (e.g., in the local memory  14  and/or the main memory storage device  16 ), such as the voltage difference lookup table  145 , that correspond to representative pixels  64  of the regions of the pixels  64  of the display  18 . 
     In process block  159 , the processor core complex  12  applies the voltage difference and a predetermined voltage of a second pixel  64  in the region having the first pixel  64  corresponding to the current to a driver TFT  118  of the second pixel  64 . That is, it may be desired for a diode  116  of the second pixel  64  to emit light of a target luminance corresponding to the current (sensed in process block  157 ). The processor core complex  12  may determine the predetermined voltage to apply to the driver TFT  118  to supply the current to the driver TFT  118  or the diode  116  of the second pixel  64  using the predetermined current-voltage relationship (e.g., stored in the local memory  14  and/or the main memory storage device  16 ). However, because the predetermined current-voltage relationship was determined under initial conditions (e.g., an initial age and temperature of the second pixel  64 ), the predetermined voltage may not compensate for operational variations with respect to the initial condition (such as aging of the second pixel  64 ). As such, the processor core complex  12  may apply a sum of the predetermined voltage and the voltage difference to the data line  124  of the second pixel  64  to compensate for the operational variations (e.g., aging) of the second pixel  64 . 
     At least during the time that hysteresis reduction (from process block  155 ), threshold voltage settling (from process block  156 ), and sensing currents (from process block  157 ) occur, it may be desirable to prevent emission of light from the diode  116  (such that a user of the electronic device  10  may not notice that these events are occurring). As such, a number of techniques may be performed to prevent emission of light from the display  18 . For example, the processor core complex  12  may adjust the electrical power supplied from the power source  28  to cease transmission of voltage along certain supply lines (although, for example, gate clock generation and transmission may be continued). As another example, the pixel  64  may include a switch that may control light emission from the pixel  64 . The processor core complex  12  may send a control signal to the switch to open or close the switch, and thus prevent voltage from being transmitted to the diode  116 . 
     Current sensing (e.g., as described in process block  157 ) may be performed multiple times to cover the display  18 . That is for each region of pixels  64  of the display  18 , the processor core complex  12  may cause the driver-integrated circuit  60  to sense current for a respective representative pixel  64  of that region of pixels  64 . Moreover, in some cases, current for the same representative pixel  64  may be sensed multiple times to improve signal-to-noise ratio, for redundancy purposes (e.g., averaging the multiple currents to filter out outlying data), and so on.  FIG.  13    is a timing diagram illustrating when data may be programmed and current may be sensed for pixels  64  of the display  18  of the electronic device  10  of  FIG.  1   , according to embodiments of the present disclosure. During a data programming period  200 , data may be programmed  202  in the pixels  64  (e.g., from pixel row  1  to pixel row N). In particular, during the data programming period  200 , the processor core complex  12  may cause the driver-integrated circuit  60  to apply a test voltage to at least the pixels  64  in which current may be sensed (e.g., each representative pixel  64  of the regions of pixels  64 ). 
     After the data programming period  200  is complete, during a current sensing time period  204 , current may be sensed  206  in certain pixels  64 . In particular, during the current sensing time period  204 , the processor core complex  12  may cause the driver-integrated circuit  60  to reduce hysteresis in the driver TFTs  118  (from process block  155 ), settle the threshold voltage in the driver TFTs  118  (from process block  156 ), and sense current across the driver TFTs  118  or the diodes  116  of each representative pixel  64  of the regions of pixels  64  (from process block  157 ). In some embodiments, because the data programmed in certain pixels  64  (e.g., pixel row N) remains in those pixels  64  for a time period  208  greater than a time period  210  of data programmed in other pixels  64  (e.g., pixel row  1 ), the timing of the data programming  202  and/or the current sensing  206  may be adjusted such that the difference in time periods  208 ,  210  is approximately the same. Moreover, it should be understood that there are gaps  212  in the timing diagram that may be used to perform other functions, such as other display functions or touch functions (e.g., registering, identifying, or locating a touch on the display  18 ). 
     In some embodiments, the electronic device  10  may implement an “Always-On” display, such that at least a portion of the display  18  is on during sleep mode. For example, during sleep mode, the display  18  may display an Always-on image that provides certain information that may be interesting or useful to the user, such as the time, date, battery status, notifications, screensavers, and so on. To support the Always-On display, the electronic device  10  and/or the display  18  may include multiple power planes. The Always-On image may be displayed on different power planes at different times, such that off-time sensing (including reducing hysteresis and settling the threshold voltage in the driver TFT  118 ) may be performed on a power plane that is not displaying the Always-On image. For example, the Always-On image may be sequentially rotated among the power planes (e.g., displayed on a first power plane but not the other power planes for a time period, displayed on a second power plane but not the other power planes for the time period, and so on). The sleep mode may be a low power mode of the display  18  and/or device  10  in which certain components of the display  18  and/or device  10  may consume less power and/or be turned off completely to save power. 
       FIGS.  14  and  15    are schematic diagrams of implementations of power rail architecture supporting an Always-On display  220  of the electronic device  10  of  FIG.  1   , according to embodiments of the present disclosure. As illustrated, the Always-On display  220  includes three power planes  222 , but any suitable number of power planes (e.g., 2-100 power planes, 5-10 power planes, and so on) is contemplated to support the Always-On display  220 . The processor core complex  12  displays the Always-On image  224  on the second or middle power plane  222 , and, as such, the processor core complex  12  may perform off-time sensing (including causing the driver-integrated circuit  60  to reduce hysteresis and settle the threshold voltage in the driver TFT  118 ) in the other power planes  222  (e.g., the first or top power plane  222  and the third or bottom power plane  222 ). 
     The first implementation shown in  FIG.  14    enables providing 0 V to the voltage rail supplying the negative power supply voltage V SSEL    120  of 0, 1 V to the voltage rail supplying the positive supply voltage V DDEL    128  of 1 V, −1 V to the voltage rail supplying the emission voltage EM, and −1 V to the voltage rail supplying the scan voltage, as referred to in pixel diagram  FIG.  9   . Each power plane  222  may receive a separate emission voltage EM, scan voltage, and negative power supply voltage V SSEL    120  from the illustrated power rails and selection circuitry. Additionally, for each power plane  222 , the processor core complex  12  and/or the driver-integrated circuit  60  may select between a normal emission signal (“EM_normal”) and an off-time sensing emission signal (“EM_ots”), a normal scan signal (“SC1_normal”) and an off-time sensing scan signal (“SC1_ots”), and the V SSEL    120  signal or a ground signal based on a one-bit selection signal input to a respective multiplexer (e.g.,  226 ) indicating whether off-time sensing is being performed (“OTS”). 
     In some cases, it may be desirable to reduce or minimize the amount of space taken up by the power rails and selection circuitry shown in  FIG.  14   . As such,  FIG.  15    illustrates a second implementation of power rail architecture supporting the Always-On display  220 . In particular, each power plane  222  may receive a separate negative power supply voltage V SSEL  or positive power supply voltage (e.g., V DDEL =V SSEL +1) from the illustrated power rails and selection circuitry. That is, for each power plane  222 , the processor core complex  12  and/or the driver-integrated circuit  60  may select between the V SSEL    120  signal or the positive power supply voltage based on a one-bit selection signal input to a respective multiplexer (e.g.,  226 ) indicating whether off-time sensing is being performed (“OTS”). The voltage rails supplying the emission voltage EM and the scan voltage may also use the illustrated power rails and selection circuitry, thus reducing the amount of space taken up by the power rails and selection circuitry when compared to the implementation shown in  FIG.  13   . 
     As discussed above, hysteresis reduction, threshold voltage settling, and current sensing of the driver TFT  118  may be advantageously performed during off-time of the display  18 . Moreover, performance of these processes may be abandoned when the electronic device  10  becomes active (e.g., a user turns on or attempts to use the device  10 ). These processes may also preferably be performed when the device  10  has sufficient power (e.g., is charging or has sufficient charge in a coupled battery), and when the temperature is sufficiently stable, since temperature changes or gradients may affect the accuracy of current measurements. 
       FIG.  16    is process  240  for determining an appropriate time to sense and store voltage differences used to compensate for operational differences (e.g., aging) of the display  18  of the electronic device  10  of  FIG.  1   , according to embodiments of the present disclosure. While the process  240  is described using steps in a specific sequence, it should be understood that the present disclosure contemplates that the describe steps may be performed in different sequences than the sequence illustrated, and certain described steps may be skipped or not performed altogether. In some embodiments, the process  240  may be implemented by executing instructions stored in a tangible, non-transitory, computer-readable medium, such as the local memory  14  and/or the main memory storage device  16 , using a processor, such as the processor core complex  12 , and, in particular, the image correction circuitry  52  and/or the aging/temperature determination circuitry  56  of the processor core complex  12  shown in  FIG.  7   . 
     As illustrated, in decision block  242 , the processor core complex  12  determines whether a usage time of the display  18  and/or the device  10  has exceeded a normal compensation time threshold. In particular, the processor core complex  12  may control a usage timer that counts the amount of time the display  18  and/or the device  10  has been used after a previous time that the processor core complex  12  sensed and stored voltage differences (e.g., in a lookup table or map stored in the local memory  14  and/or the main memory storage device  16 , such as the voltage difference lookup table  145 ) to compensate for operational differences (e.g., aging) of the display  18 . The normal compensation time threshold may be any suitable time period that the processor core complex  12  may refresh or update the voltage difference lookup table  145 , such as 1 day, 1 week, 2 weeks, 1 month, 3 months, 6 months, 1 year, and so on. 
     If the processor core complex  12  determines that the usage time of the display  18  and/or the device  10  has not exceeded the normal compensation time threshold, the processor core complex  12  returns to decision block  242  and repeats. Once the processor core complex  12  determines that the usage time of the display  18  and/or the device  10  has exceeded the normal compensation time threshold, in decision block  244 , the processor core complex  12  determines whether the usage time of the display  18  and/or the device  10  has exceeded an urgent compensation time threshold. The urgent compensation time threshold may be any suitable time period that the processor core complex  12  may refresh or update the voltage difference lookup table  145 , but may be greater than the normal compensation time threshold. In particular, while the normal compensation time threshold may represent a normal or typical period of time that a refresh of the voltage differences should occur, the urgent compensation time threshold may represent a more urgent or pressing period of time that the refresh of the voltage differences should occur, because the older the voltage differences lookup table  145  is used and not current, the more likely image data displayed on the display  18  using the voltage differences as compensation values may generate undesirable image artifacts. As such, the urgent compensation time threshold may be 1 day, 1 week, 2 weeks, 1 month, 3 months, 6 months, 1 year, and so on, as long as the urgent compensation time threshold is greater than the normal compensation time threshold. For example, in one embodiment, the normal compensation time threshold may be 45 days, while the urgent normal compensation time threshold may be 60 days. 
     If the processor core complex  12  determines that the usage time of the display  18  and/or the device  10  has exceeded the urgent compensation time threshold, then, in decision block  246 , the processor core complex  12  determines whether it is nighttime. In particular, the processor core complex  12  may determine whether the current time is indicative of a lack of use of the display  18  and/or the device  10 . For example, the processor core complex  12  may determine whether the time is between 3 AM and 5 AM. In some embodiments, the processor core complex  12  may generate a usage pattern of the display  18  and/or the device  10 , and determine whether the current time corresponds to a usage pattern where the display  18  and/or the device  10  is typically not being used. If the processor core complex  12  determines that it is not nighttime, the processor core complex  12  returns to decision block  242  and repeats. 
     If the processor core complex  12  determines that it is nighttime, in decision block  248 , the processor core complex  12  determines whether there has been a lack of movement and noise for at least two hours. In particular, the processor core complex  12  may use sensors (including audio and/or movement sensors) to determine whether the device  10  is in an environment where use of the display  18  and/or the device  10  is unlikely. The lack of movement and/or noise for a period of time may indicate that use of the display  18  and/or the device  10  is unlikely. While two hours is used as a time threshold, any suitable time threshold may be used to determine whether the device  10  is in an environment where use of the display  18  and/or the device  10  is unlikely. If the processor core complex  12  determines that there has not been a lack of movement and noise for at least two hours, then the processor core complex  12  returns to decision block  242  and repeats. If the processor core complex  12  determines that there has been a lack of movement and noise for at least two hours, then, in decision block  250 , the processor core complex  12  determines whether the device  10  is charging or whether a battery of the device  10  has sufficient charge (to sense and store an updated voltage differences lookup table  145 ). 
     Returning to decision block  244 , if the processor core complex  12  determines that the usage time of the display  18  and/or the device  10  has not exceeded the urgent compensation time threshold, then in decision block  252 , the processor core complex  12  determines whether there has been a lack of movement and noise for at least 30 minutes. In particular, the processor core complex  12  may use sensors (including auditory and/or movement sensors) to determine whether the device  10  is in an environment where use of the display  18  and/or the device  10  is unlikely. The lack of movement and/or noise for a period of time may indicate that use of the display  18  and/or the device  10  is unlikely. While 30 minutes is used as a time threshold, any suitable time threshold may be used to determine whether the device  10  is in an environment where use of the device  10  is unlikely. If the processor core complex  12  determines that there has not been a lack of movement and noise for at least 30 minutes, then the processor core complex  12  returns to decision block  242  and repeats. 
     If the processor core complex  12  determines that there has been a lack of movement and noise for at least 30 minutes, then, in decision block  250 , the processor core complex  12  determines whether the device  10  is charging (e.g., is plugged in) or whether a battery (e.g., external or internal) of the device  10  has sufficient charge (to sense and store an updated voltage differences lookup table  145 ). If the processor core complex  12  determines that the device  10  is not charging or that the battery does not have sufficient charge, then the processor core complex  12  returns to decision block  242  and repeats. If the processor core complex  12  determines that the device  10  is charging or that the battery has sufficient charge, then, in decision block  254 , the processor core complex  12  determines whether the temperature at the display  18  and/or the device  10  is sufficiently stable. That is, because temperature changes or gradients may affect the accuracy of current sensing, the processor core complex  12  may determine whether the temperature is sufficiently stable to sense current accurately. For example, the processor core complex  12  may determine whether temperature is changing by any suitable threshold amount during the process  240  (e.g., by 0.01 to 20 degrees Celsius, 1 to 10 degrees Celsius, 1 to 5 degrees Celsius, and so on). In one embodiments, the threshold amount may be 1 degree Celsius or 2 degrees Celsius. 
     If the processor core complex  12  determines that the temperature at the display  18  and/or the device  10  is not sufficiently stable, then the processor core complex  12  returns to decision block  242  and repeats. If the processor core complex  12  determines that the temperature at the display  18  and/or the device  10  is sufficiently stable, then, in process block  256 , the processor core complex  12  causes the driver-integrated circuit  60  to sends a hysteresis-reducing signal, sends a settling voltage signal, and sense current at the display  18 . In particular, the driver-integrated circuit  60  may send the hysteresis-reducing signal to each driver TFT  118  of each representative pixel  64  of each region of pixels  64  of the display  18  (e.g., as described in process block  155  of  FIG.  11   ), send the settling voltage signal to each driver TFT  118  (e.g., as described in process block  156  of  FIG.  11   ), and sense current across each driver TFT  118  or diode  116  of each representative pixel  64  of each region of pixels  64  of the display  18  (e.g., as described in process block  157  of  FIG.  11   ). 
     While sending the hysteresis-reducing signal, sending the settling voltage signal, and/or sensing the current at the display  18 , in decision block  258 , the processor core complex  12  determines whether there is an indication that the display  18  and/or the device  10  is about to be used or in use. For example, the processor core complex  12  may receive an indication (e.g., sensor information) from movement sensors of the electronic device  10  that the device  10  is being picked up, an indication (e.g., an input signal) from an input structure  22  (e.g., an on/off button) that the display  18  and/or the device  10  is being turned on, an indication (e.g., sensor information) from audio sensors that the display  18  and/or the device  10  is being voice-activated, and so on. If the processor core complex  12  determines that there is an indication that the display  18  and/or the device  10  is about to be used or in use, then the processor core complex  12  interrupts the processes of reducing the hysteresis, settling the threshold voltage, and/or sensing the current at the display  18 , and returns to decision block  242  and repeats. If the processor core complex  12  determines that there is not an indication that the display  18  and/or the device  10  is about to be used or in use, then the processor core complex  12 , then, in process block  260 , the processor core complex  12  stores the voltage differences determined during current sensing from process block  260  in an updated voltage difference lookup table or map  145 , and resets the usage timer. In this manner, the process  240  may determine an appropriate time to sense and store voltage differences used to compensate for operational differences (e.g., aging) of the display  18 . 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure. 
     The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Metadata:
Filing Date: 20200226
Publication Date: 20241105
Grant Date: 20241105
Priority Date: 20190419
Inventors: NHO, HYUNWOO
CHOI, MYUNGJOON
KIM, HYUNSOO
JANGDA, MOHAMMAD ALI
RYU, JIE WON
SHEN, Shiping
BRAHMA, KINGSUK
WANG, CHAOHAO
YAO, WEI H.
PAI, ALEX H.
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2310/0262", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0251", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0842", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3233", "inventive": true, "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": "G09G2310/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0251", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0842", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0262", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0295", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3258", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/3233", "inventive": true, "first": true, "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": "G09G2310/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0262", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0251", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0842", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3233", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3258", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 72832751