PATENT DOCUMENT

Publication Number: US-11380231-B2
Application Number: US-201816644932-A
Country: US
Kind Code: B2

Title: Display off-time sensing

Abstract:
Electronic devices and methods for compensating for aging or other effects in a display during a non-transmitting state (off state) of the display. Sensing may include emissive element sensing of the display and/or thin film transistor sensing of the display. Compensating for the effects may preserve or increase a uniformity of transmission of the display.

Claims:
What is claimed is: 
     
       1. A method comprising:
 tracking usage of a display using a display usage time counter; 
 determining whether the display usage time counter has surpassed a first threshold and whether the display is off; 
 upon determining that the display usage time counter has surpassed the first threshold and that the display is off, sensing the display to obtain a compensation value, wherein sensing the display comprises sensing current through an emissive element of the display to determine a compensation voltage as the compensation value used to obtain a target current; 
 determining whether the display usage time counter has surpassed a second threshold and whether the display is off; 
 upon determining that the display usage time counter has surpassed the second threshold and that the display is off, determining whether the display is connected to external power; 
 upon determining that the display is connected to external power, that the display is off, and that the display usage time counter has surpassed the second threshold, sensing the display to obtain the compensation value; and 
 driving the display based at least in part on the compensation value. 
 
     
     
       2. The method of  claim 1 , wherein the compensation voltage is configured to offset effects of aging on the emissive element. 
     
     
       3. The method of  claim 1 , wherein the emissive element comprises a self-emissive element. 
     
     
       4. The method of  claim 3 , wherein the self-emissive element comprises an organic light emitting diode. 
     
     
       5. The method of  claim 1 , comprising, upon determining that the display usage time counter has not surpassed the first threshold or that the display is not off, delaying sensing until at least a next available sensing period. 
     
     
       6. The method of  claim 1 , comprising, upon determining that the display usage time counter has not surpassed the second threshold or that the display is not off, delaying sensing until at least a next available sensing period. 
     
     
       7. Non-transitory, computer-readable, and tangible medium storing instructions thereon, that when executed, are configured to cause one or more processors to:
 set a first indication that a first sensing type for a display panel is to occur during an off period for the display panel, wherein the first sensing type comprises emissive element sensing; 
 set a second indication that a second sensing type for the display panel is to occur during the off period for the display panel, wherein the second sensing type comprises thin film transistor sensing; 
 determine whether the first sensing type and the second sensing type are to occur within a threshold time of each other; 
 upon determining that the first sensing type and the second sensing type are not to occur within the threshold time of each other, perform a first sensing having the first sensing type and perform a second sensing having the second sensing type; and 
 upon determining that the first sensing type and the second sensing type are to occur within the threshold time of each other, delay the first sensing and performing the second sensing. 
 
     
     
       8. The non-transitory, computer-readable, and tangible medium of  claim 7 , wherein the emissive element sensing comprises current sensing through an emissive element relative to a voltage drop across the emissive element to derive a compensation voltage to be added to the voltage drop to achieve a target current. 
     
     
       9. The non-transitory, computer-readable, and tangible medium of  claim 8 , wherein the compensation voltage is configured to compensate for aging of the emissive element. 
     
     
       10. The non-transitory, computer-readable, and tangible medium of  claim 7 , wherein setting the first indication comprises determining whether a usage counter has surpassed a first threshold corresponding to a battery-power or a second threshold corresponding to a line-powered condition. 
     
     
       11. The non-transitory, computer-readable, and tangible medium of  claim 7 , wherein setting the second indication comprises determining whether a usage counter has surpassed a first threshold corresponding to a battery-power or a second threshold corresponding to a line-powered condition. 
     
     
       12. A system comprising:
 a display having sensing circuitry configured to sense parameters of the display during an off state of the display, wherein sensing the display comprises sensing using emissive element sensing and sensing using thin film transistor sensing; 
 a processor; and 
 memory storing instructions that, when executed, are configured to cause the processor to: 
 cause the sensing circuitry to scan the display in a frame-by-frame basis; 
 determine whether a user interrupt has occurred during the scan;
 upon determination that no user interrupt has occurred during the scan:
 determine whether a frame of the scan has been completed; and 
 upon completion of the frame, store frame data for the frame to update compensation values for driving the display; and 
 
 upon determination that the user interrupt has occurred during the scan, abandon current frame data and begin the frame of the scan again at a later scanning opportunity. 
 
 
     
     
       13. The system of  claim 12 , wherein the parameters of the display comprise non-uniformity of the display. 
     
     
       14. The system of  claim 13 , wherein the non-uniformity of the display is a result of aging of emissive elements or transistors in the display. 
     
     
       15. The system of  claim 12 , wherein the instructions are configured to cause the processor to operate the display with the updated compensation values. 
     
     
       16. A method comprising:
 sensing a display during an off state of the display, wherein sensing the display derives compensation values to compensate for non-uniformity of the display when the display is driven and wherein sensing the display comprises sensing using emissive element sensing and sensing using thin film transistor sensing; 
 receiving an indication that the display is in an on state; 
 predicting aging during the on state based at least in part on the sensing of the display in the off state; 
 receiving an indication that the display has entered a subsequent off state; 
 re-sensing during the subsequent off state to obtain re-sensing values; and 
 adjusting prediction of aging during subsequent on states based at least in part on a difference between re-sensing values and the predicted aging. 
 
     
     
       17. The method of  claim 16 , wherein emissive element sensing comprises current sensing through an emissive element relative to a voltage drop across the emissive element to derive a compensation voltage to be added to the voltage drop to achieve a target current. 
     
     
       18. A method comprising:
 performing active panel conditioning to reduce hysteresis in pixels of a display panel during an off state of the display panel; 
 during active panel conditioning, sensing aging effects of an emissive element of the display panel; 
 after active panel conditioning and the sensing aging effects of the emissive element have completed, sensing thin film transistor aging of the display panel; 
 predicting aging during an on state based at least in part on the sensing of the display panel in the off state; 
 receiving an indication that the display panel has entered a subsequent off state; 
 re-sensing during the subsequent off state to obtain re-sensing values; and 
 adjusting prediction of aging during subsequent on states based at least in part on a difference between re-sensing values and the predicted aging.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage filing of PCT Application No. PCT/US2018/049193, filed Aug. 31, 2018, and entitled “Display Off-Time Sensing,” which is a continuation of and claims priority to U.S. Non-Provisional application Ser. No. 15/870,125, filed Jan. 12, 2018, and entitled “Display Off-Time Sensing,” which claims priority to and the benefit of U.S. Provisional Application No. 62/562,915, filed Sep. 25, 2017, and entitled “Display Off-Time Sensing,” the disclosures of which are hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     The present disclosure relates generally to techniques to sensing non-uniformity in a display. More specifically, the present disclosure relates generally to techniques for sensing non-uniformity in a display in a non-disruptive way, such as during an off state when the display is not actively displaying content. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Electronic display panels are used in a plethora of electronic devices. These display panels typically include multiple pixels that emit light. The pixels may be formed using self-emissive units (e.g., light emitting diode) or pixels that utilize units that are backlit (e.g., liquid crystal diode). The displays may be compensated for non-uniformity to reduce noise at each pixel of the display. However, sensing for non-uniformity may be affected by content-dependent noise that gives incomplete and/or incorrect compensation. 
     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. 
     Display panel uniformity may be negatively impacted by various parameters (e.g., aging) of the display panel. The display panel uniformity may be improved by sensing for non-uniformity (e.g., aging effects) in a display during an off time of the display to avoid content-based changes to compensation results from the non-uniformity sensing. Furthermore, off-time sensing may reduce battery life of some devices. Thus, a first threshold may be used for determining when to perform off-time sensing during battery-powered conditions, and a second threshold may be set to perform off-time sensing during externally powered conditions. Furthermore, in some embodiments, off-time sensing may be reserved for externally powered conditions. 
     Moreover, non-uniformity sensing may be divided into thin-film transistor (TFT) sensing and emissive element (e.g., organic light emitting diode—OLED) sensing. Since TFTs exhibit aging effects more quickly, TFT sensing may be performed more frequently than emissive element sensing. To avoid overuse of battery power, when TFT sensing and emissive element sensing are to occur within a same time period (e.g., 1 day), the sensing with the lower frequency (e.g., emissive element sensing) of sensing may be delayed until a next period (e.g., next day). 
     Sensing noise reduction may utilize multiple scans of each display pixel. Some displays (e.g., mobile phone) may also be switched on and off more frequently than other displays (e.g., television, computer monitors, etc.) In a frequently switched display, the interruption of off-time sensing may cause some data to be lost when only a portion of the pixels of the display are scanned or may cause the sensing to include disadvantageous temporal variations. Instead of scanning each pixel consecutively before moving on to other pixels, some embodiments may include scanning an entire frame before moving to a next frame. Furthermore, if a frame completes, the results of the frame may be saved (even if the scanning process is not fully completed). Only frames that have not completed are discarded since spatial continuity in each frame is preserved at an approximately consistent time. In other words, pixels in the same frame are likely under similar temporal conditions, but pixels before and after an interruption may have quite different temporal conditions. Thus, a frame may be used to group pixels sensing values in approximately consistent temporal conditions. 
     Some display devices (e.g., desktop monitors, mobile phones) may not experience off-times that are long enough to complete non-uniformity scanning. Thus, in some embodiments, compensation may be predicted/estimated while the display is on between off-time sensing processes. Furthermore, the prediction of the changes (e.g., due to panel aging) may be corrected/fine-tuned based on predicted changes versus measured changes after a scan has been completed. Furthermore, in some embodiments, at least some sensing may overlap at least a portion of other operations (e.g., active panel conditioning) during the off time for the display panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a schematic block diagram of an electronic device including a display, in accordance with an embodiment; 
         FIG. 2  is a perspective view of a notebook computer representing an embodiment of the electronic device of  FIG. 1 , in accordance with an embodiment; 
         FIG. 3  is a front view of a hand-held device representing another embodiment of the electronic device of  FIG. 1 , in accordance with an embodiment; 
         FIG. 4  is a front view of another hand-held device representing another embodiment of the electronic device of  FIG. 1 , in accordance with an embodiment; 
         FIG. 5  is a front view of a desktop computer representing another embodiment of the electronic device of  FIG. 1 , in accordance with an embodiment; 
         FIG. 6  is a front view of a wearable electronic device representing another embodiment of the electronic device of  FIG. 1 , in accordance with an embodiment; 
         FIG. 7  illustrates a block diagram view of a current sensing scheme, in accordance with an embodiment; 
         FIG. 8  illustrates a flow diagram view of a process for using two thresholds to determine when to enable off-time sensing, in accordance with an embodiment; 
         FIG. 9  illustrates a flow diagram view of a process for using the two thresholds of  FIG. 8 , in accordance with an embodiment; 
         FIG. 10  illustrates a diagram of conflict resolution between two sensing types for a display, in accordance with an embodiment; 
         FIG. 11A  illustrates a flow diagram view of a process for conflict resolution for a first sensing type of the two sensing types of  FIG. 10 , in accordance with an embodiment; 
         FIG. 11B  illustrates a flow diagram view of a process for conflict resolution for a second sensing type of the two sensing types of  FIG. 10 , in accordance with an embodiment; 
         FIG. 12  illustrates a flow diagram view of a process for performing frame-by-frame sensing of a display, in accordance with an embodiment; 
         FIG. 13  illustrates a block diagram view of on state estimation of aging, in accordance with an embodiment; 
         FIG. 14  illustrates a flow diagram view of a process for on state estimation of aging, in accordance with an embodiment; 
         FIG. 15  illustrates a timing diagram of an off state having three sensing phases, in accordance with an embodiment; 
         FIG. 16  illustrates a timing diagram of an off state having two sensing phases, in accordance with an embodiment; 
         FIG. 17  illustrates a schematic diagram view reflecting the two sensing phases of  FIG. 16 , in accordance with an embodiment; and 
         FIG. 18  illustrates a flow diagram view performing active panel conditioning concurrently with emissive element sensing, in accordance with an embodiment. 
     
    
    
     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. 
     Display panel uniformity can be improved by sensing for non-uniformity in a display during an off time of the display to avoid content-based changes to compensation results from the non-uniformity sensing. Furthermore, off-time sensing may reduce battery life of mobile devices. Thus, a first threshold may be used for determining when to perform off-time sensing during battery-powered conditions, and a second threshold may be set to perform off-time sensing during externally powered conditions. Furthermore, in some embodiments, off-time sensing may be reserved for externally powered conditions. 
     Moreover, non-uniformity sensing may be divided into thin-film transistor (TFT) sensing and emissive element (e.g., organic light emitting diode—OLED) sensing. Since TFTs experience change more quickly, TFT sensing may be performed more frequently than emissive element sensing. To avoid overuse of battery power, when TFT sensing and emissive element sensing are to occur within a same time period (e.g., 1 day), the sensing with the lower frequency (e.g., emissive element sensing) of sensing may be delayed until a next period (e.g., next day). 
     Sensing noise reduction may utilize multiple scans of each display pixel. Some displays (e.g., mobile phone) may also be switched on and off more frequently than other displays (e.g., television, computer monitors, etc.), In a frequent switching display, the interruption of off-time may cause some data to be lost when only a portion of the pixels of the display are scanned. Instead of scanning each pixel consecutively before moving on to other pixels, some embodiments may include scanning an entire frame before moving to a next frame. Furthermore, if a frame completes, the results of the frame may be saved (even if the scanning process is not fully completed). Only frames that have not completed are discarded since spatial continuity in each frame is preserved. In other words, pixels in the same frame are likely under similar temporal conditions, but pixels before and after an interruption may have quite different temporal conditions. Thus, a frame may be used to group pixels sensing values in approximately consistent temporal conditions. 
     Some display devices (e.g., desktop monitors, mobile phones) may not experience off-times that are long enough to complete non-uniformity scanning. Thus, in some embodiments, compensation may be predicted/estimated while the display is on between off-time sensing processes. Furthermore, the prediction of the changes (e.g., due to panel aging) may be corrected/fine-tuned based on predicted changes versus measured changes after a scan has been completed. 
     With the foregoing in mind and referring first to  FIG. 1 , an electronic device  10  according to an embodiment of the present disclosure may include, among other things, one or more processor(s)  12 , memory  14 , nonvolatile storage  16 , a display  18 , input structures  20 , an input/output (I/O) interface  22 , a power source  24 , and interface(s)  26 . The various functional blocks shown in  FIG. 1  may include hardware elements (e.g., including circuitry), software elements (e.g., including computer code stored on a computer-readable medium) or a combination of both hardware and software elements. It should be noted that  FIG. 1  is merely one example of a particular implementation and is intended to illustrate the types of components that may be present in electronic device  10 . 
     In the electronic device  10  of  FIG. 1 , the processor(s)  12  and/or other data processing circuitry may be operably coupled with the memory  14  and the nonvolatile storage  16  to perform various algorithms. Such programs or instructions, including those for executing the techniques described herein, executed by the processor(s)  12  may be stored in any suitable article of manufacture that includes one or more tangible, computer-readable media at least collectively storing the instructions or routines, such as the memory  14  and the nonvolatile storage  16 . The memory  14  and the nonvolatile storage  16  may include any suitable articles of manufacture for storing data and executable instructions, such as random-access memory, read-only memory, rewritable flash memory, hard drives, and/or optical discs. Also, programs (e.g., an operating system) encoded on such a computer program product may also include instructions that may be executed by the processor(s)  12  to enable the electronic device  10  to provide various functionalities. 
     In certain embodiments, the display  18  may be a liquid crystal display (e.g., LCD), which may allow users to view images generated on the electronic device  10 . In some embodiments, the display  18  may include a touch screen, which may allow users to interact with a user interface of the electronic device  10 . Furthermore, it should be appreciated that, in some embodiments, the display  18  may include one or more light emitting diode (e.g., LED) displays, or some combination of LCD panels and LED panels. The display  18  may include sensing circuitry  19  that is used to sense non-uniformity of the display  18  by sensing changes in voltage/current through thin-film transistors (TFTs) and/or emissive elements in the display  18 . 
     The input structures  20  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, a camera to record video or capture images). The I/O interface  22  may enable the electronic device  10  to interface with various other electronic devices. Additionally or alternatively, the I/O interface  22  may include various types of ports that may be connected to cabling. These ports may include standardized and/or proprietary ports, such as USB, RS232, APPLE&#39;S LIGHTNING® connector, as well as one or more ports for a conducted RF link. 
     As further illustrated, the electronic device  10  may include the power source  24 . The power source  24  may include any suitable source of power, such as a rechargeable lithium polymer (e.g., Li-poly) battery and/or an alternating current (e.g., AC) power converter. The power source  24  may be removable, such as a replaceable battery cell. 
     The interface(s)  26  enable the electronic device  10  to connect to one or more network types. The interface(s)  26  may also include, for example, interfaces for a personal area network (e.g., PAN), such as a BLUETOOTH network, for a local area network (e.g., LAN) or wireless local area network (e.g., WLAN), such as an 802.11 Wi-Fi network or an 802.15.4 network, and/or for a wide area network (e.g., WAN), such as a 3rd generation (e.g., 3G) cellular network, 4th generation (e.g., 4G) cellular network, or long term evolution (e.g., LTE) cellular network. The interface(s)  26  may also include interfaces for, for example, broadband fixed wireless access networks (e.g., WiMAX), mobile broadband Wireless networks (e.g., mobile WiMAX), and so forth. 
     By way of example, the electronic device  10  may represent a block diagram of the notebook computer depicted in  FIG. 2 , the handheld device depicted in either of  FIG. 3  or  FIG. 4 , the desktop computer depicted in  FIG. 5 , the wearable electronic device depicted in  FIG. 6 , or similar devices. It should be noted that the processor(s)  12  and/or other data processing circuitry may be generally referred to herein as “data processing circuitry.” Such data processing circuitry may be embodied wholly or in part as software, firmware, hardware, or any combination thereof. Furthermore, the data processing circuitry may be a single contained processing module or may be incorporated wholly or partially within any of the other elements within the electronic device  10 . 
     In 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 (e.g., such as laptop, notebook, and tablet computers) as well as computers that are generally used in one place (e.g., such as conventional desktop computers, workstations and/or servers). In certain embodiments, the electronic device  10  in the form of a computer may be a model of a MACBOOK®, MACBOOK® Pro, MACBOOK AIR®, IMAC®, MAC® mini, or MAC PRO® available from APPLE INC. By way of example, the electronic device  10 , taking the form of a notebook computer  30 A, is illustrated in  FIG. 2  in accordance with one embodiment of the present disclosure. The depicted computer  30 A may include a housing or enclosure  32 , a display  18 , input structures  20 , and ports of the I/O interface  22 . In one embodiment, the input structures  20  (e.g., such as a keyboard and/or touchpad) may be used to interact with the computer  30 A, such as to start, control, or operate a GUI or applications running on computer  30 A. For example, a keyboard and/or touchpad may allow a user to navigate a user interface or application interface displayed on display  18 . 
       FIG. 3  depicts a front view of a handheld device  30 B, which represents one embodiment of the electronic device  10 . The handheld device  30 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  30 B may be a model of an IPOD® or IPHONE® available from APPLE INC. of Cupertino, Calif. 
     The handheld device  30 B may include an enclosure  32  to protect interior components from physical damage and to shield them from electromagnetic interference. The enclosure  32  may surround the display  18 , which may display indicator icons. The indicator icons may indicate, among other things, a cellular signal strength, BLUETOOTH connection, and/or battery life. The I/O interfaces  22  may open through the enclosure  32  and may include, for example, an I/O port for a hard-wired connection for charging and/or content manipulation using a connector and protocol, such as the Lightning connector provided by APPLE INC., a universal serial bus (e.g., USB), one or more conducted RF connectors, or other connectors and protocols. 
     The illustrated embodiments of the input structures  20 , in combination with the display  18 , may allow a user to control the handheld device  30 B. For example, a first input structure  20  may activate or deactivate the handheld device  30 B, one of the input structures  20  may navigate user interface to a home screen, a user-configurable application screen, and/or activate a voice-recognition feature of the handheld device  30 B, while other of the input structures  20  may provide volume control, or may toggle between vibrate and ring modes. Additional input structures  20  may also include a microphone that may obtain a user&#39;s voice for various voice-related features, and a speaker to allow for audio playback and/or certain phone capabilities. The input structures  20  may also include a headphone input (not illustrated) to provide a connection to external speakers and/or headphones and/or other output structures. 
       FIG. 4  depicts a front view of another handheld device  30 C, which represents another embodiment of the electronic device  10 . The handheld device  30 C may represent, for example, a tablet computer, or one of various portable computing devices. By way of example, the handheld device  30 C may be a tablet-sized embodiment of the electronic device  10 , which may be, for example, a model of an IPAD® available from APPLE INC. of Cupertino, Calif. 
     Turning to  FIG. 5 , a computer  30 D may represent another embodiment of the electronic device  10  of  FIG. 1 . The computer  30 D may be any computer, such as a desktop computer, a server, or a notebook computer, but may also be a standalone media player or video gaming machine. By way of example, the computer  30 D may be an IMAC®, a MACBOOK®, or other similar device by APPLE INC. It should be noted that the computer  30 D may also represent a personal computer (e.g., PC) by another manufacturer. A similar enclosure  32  may be provided to protect and enclose internal components of the computer  30 D such as the display  18 . In certain embodiments, a user of the computer  30 D may interact with the computer  30 D using various peripheral input devices, such as the keyboard  37  or mouse  38 , which may connect to the computer  30 D via an I/O interface  22 . 
     Similarly,  FIG. 6  depicts a wearable electronic device  30 E representing another embodiment of the electronic device  10  of  FIG. 1  that may be configured to operate using the techniques described herein. By way of example, the wearable electronic device  30 E, which may include a wristband  43 , may be an APPLE WATCH® by APPLE INC. However, in other embodiments, the wearable electronic device  30 E may include any wearable electronic device such as, for example, a wearable exercise monitoring device (e.g., pedometer, accelerometer, heart rate monitor), or other device by another manufacturer. The display  18  of the wearable electronic device  30 E may include a touch screen (e.g., LCD, an organic light emitting diode display, an active-matrix organic light emitting diode (e.g., AMOLED) display, and so forth), which may allow users to interact with a user interface of the wearable electronic device  30 E. 
     Although the following discusses sensing current through an OLED as a pixel, some embodiments may include measuring other parameters suitable for other pixel types. For example, LED voltage may be sensed at LED pixels in the display. 
       FIG. 7  illustrates a block diagram view of a current sensing scheme  100  in the sensing circuitry  19  of the display  18  used to sense changes in a display panel  101  of the display  18 . As illustrated, a target pixel current is provided via a current source  102 . The current provided by the current source  102  then is supplied to a current sensing system  104  via sensing channel(s)  106 . The sensing channel  106  may include single-ended or a differential channel(s). The current sensing system  104  then outputs an output  108  that is used to compensate display panel operation. In other words, in the current sensing scheme  100 , a channel  106  is used to detect or estimate pixel current directly from a target pixel. Furthermore, the current sensing scheme  100  may also be used to detect or estimate current and/or voltages of TFTs of the display panel. In such sensing modes, current through the emissive element of the pixel may be avoided by switching one more switches (e.g., TFTs). Additionally, the current sensing (i.e., emissive element sensing) may be performed using a relatively low current/voltage to reduce likelihood of detection of the sensing on the display panel  101 . Furthermore, in some embodiments, TFT sensing may utilize low currents/voltages to reduce likelihood of visibility of the sensing. Moreover, the current sensing scheme  100  may include amplifiers, filters, analog-to-digital converters, digital-to-analog converters, and/or other circuitry used for processing in the current sensing scheme  100  that have been omitted from  FIG. 7  for clarity. 
     As previously noted, non-uniformity sensing for some displays may be unsuitable for other displays. For example, sensing schemes used on devices that are always powered by external power may be unconcerned with available power. Thus, such schemes may not be suitable for displays that use an internal power source (e.g., battery). Instead, in displays that utilize limited power (e.g., battery), prioritization of sensing based on thresholds and available power may be used. 
       FIG. 8  illustrates a dual-threshold process  120  used for sensing in the sensing circuitry  19  and/or the processor(s)  12 . Although the following discusses that the sensing circuitry  19  performs various steps, at least a portion of the steps attributed to the sensing circuitry  19  may be performed using some processing from the processor(s)  12 . With this is mind, the sensing circuitry  19  tracks display usage using a display usage time counter  122 . The display usage time counter  122  may track how long the display has been on either as an overall number of usage for the display  18  or as a relative number of usage of the display  18  only since a last sensing. The sensing circuitry  19  then determines whether this display usage time counter  122  has surpassed a first threshold (block  124 ). If the display usage time counter  122  has exceeded this first threshold the sensing circuitry  19  determines whether the display  18  is off (block  126 ). If the display  18  is off, the sensing circuitry  19  begins performing sensing (block  128 ). However, when the display  18  is on and/or when the display usage time counter  122  has surpassed the first threshold, the sensing circuitry  19  delays the sensing to a next round sensing (block  129 ). 
     In addition to the first threshold, the sensing circuitry  19  may utilize a second threshold. The first threshold may correspond to a high number (e.g., a long period of use) relative to the second threshold. The second threshold may be utilized to cause sensing when more power is available. For example, the second threshold may be used to provide sensing when AC power is connected to the electronic device  10  before the first threshold causes sensing regardless of external power availability. 
     The sensing circuitry  19  determines whether the display usage time counter  122  has surpassed the second threshold (block  130 ). If the display usage time counter  122  has surpassed the second threshold, the sensing circuitry  19  determines whether the display  18  is off (block  132 ). If the display  18  is off, the sensing circuitry  19  determines whether the electronic device  10  is plugged into an external power supply (block  134 ). For example, the electronic device may be powered using an external AC adapter in addition to or alternative to battery power. If external power is provided to the electronic device  10 , the sensing circuitry  19  performs the sensing scan, as previously discussed (block  136 ). However, if the sensing circuitry determines that the display usage time counter  122  has not surpassed second threshold, the display is on, and/or the electronic device is not plugged into external power, the sensing circuitry  19  delays sensing until a next round sensing. In some embodiments, the first and second thresholds may be evaluated in a different order. For example, in certain embodiments, the second threshold may be evaluated before the first threshold is evaluated to prefer evaluating whether a plugged sensing threshold should be used before determining whether a non-plugged sensing threshold should be used. Additionally or alternatively, in some embodiments, a determination may be made to determine whether the display is receiving external power before using a threshold. In certain such embodiments, only a single threshold may be used with the first threshold used when external power is not connected and the second threshold used when external power is connected. 
     As previously discussed, sensing may include various sensing types. For example, a first sensing type may be used to sense aging in TFTs and a second sensing type may be used to sense aging of emissive elements. Since TFTs and emissive elements may reflect aging changes at different rates, these sensing processes may occur at different intervals. Thus, the two sensing types may be scheduled to occur at different times, but, in some embodiments, these schedules may conflict (e.g., occur at the same time). When both sensing types are to occur at the same time and/or within a same duration, drain on an internal power supply (e.g., battery) may be excessive. 
     Thus, the sensing circuitry  19  may utilize some conflict resolution between the two sensing process types.  FIG. 9  illustrates a process  150  that may be used to resolve these conflicts. The sensing circuitry  19  sets a first indication that a first sensing type is to occur (block  152 ). For example, a first sensing type may include emissive element sensing, such as sensing an aging of an organic light emitting diode (OLED). The sensing circuitry  19  may also set a second indication that a second sensing type is to occur (block  154 ). The second sensing type may include sensing of TFTs in the display  18 . The sensing circuitry  19  may determine whether both of these sensing types are to occur within a threshold time (block  156 ). For example, the threshold time may include a duration in which battery drain is potentially excessive by performing both sensing types within the threshold time. For instance, the threshold time may include a number of seconds, minutes, hours, days, or weeks. 
     If both sensing types do not occur within the threshold time, the sensing circuitry  19  may perform both sensing types at the indicated corresponding times (block  158 ). However, both sensing types are to occur within the threshold time, the sensing circuitry  19  may delay the first sensing type to a later time (block  160 ). The sensing type to be delayed may be selected based on which sensing type has a longer interval between sensing occurrences. For example, a sensing type that occurs less frequently may be delayed because the underlying sensed parameter may reflect aging changes less frequently. For instance, aging of the emissive elements may be less severe in appearance than the changes caused by aging of TFTs. Thus, in some embodiments, sensing of emissive elements may be delayed until later time while the second sensing type may still be performed by the sensing circuitry  19  (block  162 ). 
       FIG. 10  illustrates a timing diagram  170  of two sensing types. The timing diagram illustrates TFT sensing  172 . The sensing circuitry  19  may also set an indicator  174  that indicates that the TFT sensing  172  is to occur. For example, the indicator  174  may include a flag in the memory  14  indicating a specific time or window in which the sensing is to occur. Additionally or alternatively, the indicator  174  may indicate that the sensing is to be applied at a next available sensing possibility. The timing diagram  170  also illustrates sensing for an emissive element such as an OLED sensing  176 . The OLED sensing  176  may also utilize an indicator  178  that indicates when the OLED sensing  176  is to occur. At point in time  180 , an indication  174  is set for TFT sensing  172 , and an indication  178  is set for an OLED sensing  176 . As illustrated, the indicators  174  and  178  occur at the same time or within the time threshold. To alleviate power issues due to off-time sensing using two different sensing types, the sensing circuitry  19  delays OLED sensing  176  by a duration  182 . The duration  182  may be equal to the time threshold or maybe a separate value. 
       FIGS. 11A and 11B  illustrate processes  190  and  200  used to implement the conflict resolution of  FIGS. 9 and 10 . The process  190  includes resetting a TFT aging counter (block  192 ). This reset may be used to track usage of the display  18  since a last TFT sensing  172 . The sensing circuitry  19  then counts usage for display  18  by incrementing the TFT aging counter (block  194 ). The sensing circuitry  19  then determines whether this TFT aging counter has invoked a TFT flag (block  196 ). For example, the TFT flag may be invoked as the indicator  174  once the TFT aging counter has reached a threshold. In some embodiments, the threshold may include the first threshold or the second threshold in accordance with the discussion related to  FIG. 8 . 
     Once the TFT flag is set, the sensing circuitry  19  performs TFT sensing (block  198 ). Once TFT sensing has been performed, the sensing circuitry  19  resets the counter and may begin the process  190  over again. 
     Similar to the process  190 , the sensing circuitry  19  utilizes process  200  to control OLED sensing  176 . The sensing circuitry  19  reset an OLED aging counter ( 202 ). Using the reset OLED aging counter, the sensing circuitry  19  tracks usage of the display  18  using OLED aging counting (block  204 ). The sensing circuitry  19  then determines whether the OLED flag has been set and the TFT flag has not been set (block  206 ). Similar to setting of the TFT flag, the sensing circuitry  19  may determine whether the OLED aging counter has surpassed the first and/or second threshold as discussed in  FIG. 8  previously. If the OLED flag is set and the TFT flag is not set, OLED sensing is performed (block  208 ). However, if the OLED flag is not set or the TFT flag is set, the sensing circuitry  19  continues counting OLED aging. In some embodiments, the sensing circuitry  19  may temporarily increment the threshold setting to ensure that the OLED sensing  176  only occurs after the duration  182  elapses after the corresponding TFT sensing  172 . 
     As previously discussed, a sensing scan may use more than a single pass of pixels of the display  18 . However, the display  18  may be turned on during scans. Accordingly, data gathered in an incomplete sensing may not be completely useful for compensating for non-uniformity since an incomplete scan of the display  18  with subsequent completion may capture different display parameters under disparate conditions. For example, temperature and/or aging variations may cause the pixels of the display  18  to behave differently due to scans being run at different times. Instead, at least a portion of the incomplete scans may be discarded. Specifically, if a scan includes scanning each pixel more than once before moving on to a next pixel, the scan may be more likely to cause discarding of a relatively high number of pixel data. Instead, a scan may include one or more frames where each pixel is scanned before moving on to a next state. Thus, a first pass of the sensing circuitry  19  may be kept even if later frames are not completed.  FIG. 12  illustrates a process  220  for applying sensing scans in a frame-by-frame manner. The sensing circuitry  19  starts a new frame starting a first pixel (block  222 ). For example, the new frame may be a first frame of a sensing scan. Moreover, the new frame may begin in a first corner of the display  18  (e.g., top-left corner) and end in another corner of the display  18  (e.g., bottom-right corner). The sensing circuitry  19  conducts sensing in the first frame (block  224 ). The sensing circuitry  19  and/or the processor(s)  12  may determine whether a user interrupt has occurred (block  226 ). For example, the sensing circuitry  19  and/or the processor(s)  12  may determine whether input structures  20  have been used to awaken the display  18  from an off state. 
     When no user interrupt has been detected, the sensing circuitry  19  and/or the processor(s)  12  determines whether the frame is finished (block  228 ). If the frame has not been completed, the sensing circuitry  19  continues sensing the frame. Once the frame has been completed, the sensing circuitry  19  and/or the processor(s)  12  store frame data to be used for compensating operation of the display  18  (block  230 ). The frame data may be stored in the memory  14 . The sensing circuitry  19  may indicate that the sensing operation has update compensation values (block  232 ). The processor(s)  12  then use the updated compensation values from memory  14  to compensate for non-uniformity in the display  18  (block  234 ). 
     If the sensing circuitry  19  and/or the processor(s)  12  determine that a user interrupt has occurred before the currently scanned frame has been completed, the sensing circuitry  19  and/or the processor(s)  12  abandon current frame data (block  236 ). For example, the sensing circuitry  19  and/or the processor(s)  12  may delete the frame data from volatile memory prior to storing compensation values in non-volatile memory. Additionally or alternatively, frame data may be stored in non-volatile memory during a scan, but the signal to indicate that the frame has not completed is suppressed. Furthermore, the frame data in the non-volatile memory may be deleted. Moreover, in some embodiments, the frame data may be deleted if a threshold of time has elapsed since a frame has begun without completing the frame. Once frame data has been discarded, the sensing circuitry  19  looks for a next sensing opportunity (block  238 ). For example, the sensing circuitry  19  may wait until the display  18  is turned off to start a new frame scan. In some embodiments, the sensing circuitry  19  may wait until a threshold of time has elapsed from the last on state during the current off-time before attempting to scan a new frame again. 
     Since sensing frames are performed during an off-state, the compensation values for the display  18  may not be updated while the display  18  is on. In some situations, the display  18  may remain on for an extended duration. During this duration, the display  18  uniformity may decrease without adjusted compensation being applied. To address this situation, the processor(s)  12  may estimate compensation while the display  18  is on.  FIG. 13  illustrates a process  250  used to estimate compensation changes during sequential on and off states. During an off state  252  for the display  18 , the sensing circuitry  19  performs Off-time sensing  254 . During a later on state  258 , the processor(s)  12  and/or the sensing circuitry  19  uses the Off-time sensing  254  to calculate an aging prediction  256 . This aging prediction  256  is then added to the results of the Off-time sensing  254  to generate the on time compensation  260  to drive the display  18  during the on state  258  since the aging of the display  18  only increases during the on state  258 . 
     Furthermore, the aging prediction  256  is used to fine tune previous on time compensations since the aging prediction  256  is a difference between Off-time sensing  254  and a previous on time compensation. Similarly, the on time compensation  260  may be used in future compensations. For example, during a subsequent off state  262 , the sensing circuitry  19  performs Off-time sensing  264 . The results of this sensing scan are subtracted from the previous on time compensation  260  to calculate the aging prediction  266 . In other words, the aging prediction  266  is based on how far off the on time compensation  260  is from the values determined during the Off-time sensing  264 . During the on state of the display  18 , the aging prediction  266  is added to the results of the Off-time sensing  264  to generate the on time compensation  270 . 
     Running compensation  272  illustrates how the past values are used to predict future aging compensation. The running compensation  272  receives real-time content  274  into an accumulator  276  that tracks on time for the display  18  and the usage of the display  18  based on the real-time content  274  since a previous Off-time sensing. Real-time content  274  may include content as it is being displayed. Additionally or alternatively, the real-time content  274  may include any data since a last Off-time sensing within a period of time small enough that the aging effects on the display may be small and/or unnoticeable to a user. The accumulator  276  also receives temperature information  278  and brightness level  280  that are both relevant to usage and/or aging. The real-time content  274  since the last Off-time sensing is accumulated and passed to conversion circuitry  282  that maps grayscale levels in the real-time content to a correction voltage based on the temperature information  278 , the brightness level  280 , and difference between a previous prediction and a present sensing  284 . In other words, the conversion circuitry  282  may calculate a correction voltage that is used to offset predicted aging in the display  18  due to the real-time content  274  displayed at a temperature indicated in the temperature information  278  at the brightness level  280 . This correction voltage is also fine-tuned by indicating how much the previous prediction using the calculation varied from the sensed correction voltage level. 
       FIG. 14  illustrates a process  300  used to implement on time aging estimation. The sensing circuitry  19  senses the display  18  during an off state for the display  18  (block  302 ). The processor(s)  12  receive an indication that the display is an on state (block  304 ). For example, the processor(s)  12  may receive an indication to turn the display  18  on via the input structures  20 , send a signal to turn on the display  18 , and receive a return signal as the indication that the display  18  has entered the on state. The processor(s)  12  then predict aging during the on state based on the off-time sensing (block  306 ). The prediction may be based on real-time content since the off-time sensing, brightness level for the display  18 , temperature information, and/or a difference between the results of the off-time sensing and a previous estimation of aging. 
     The processor(s)  12  receive an indication that the display  18  has entered into a subsequent off state (block  308 ). During the subsequent off state, the sensing circuitry  19  re-senses the display  18  (block  310 ). The processor(s)  12  and/or the sensing circuitry  19  adjust prediction of aging during subsequent on states of the display  18  based at least in part on a difference between re-sense aging values and the predicted aging (block  312 ). The prediction of aging during subsequent on states may also be based at least in part on real-time content since the off-time sensing, brightness level for the display  18 , and/or temperature information. 
     Since the TFTs and related circuitry (e.g., capacitors) in the display  18  may include some hysteresis, the processor(s)  12  may utilize active panel conditioning to toggle the TFTs to reduce previous content&#39;s impact to TFT characteristics during the TFT sensing.  FIG. 15  illustrates a timing diagram  330  that may be used for the display  18 . The timing diagram  330  illustrates that the display  18  may be in an on state  332  and then an off state  334 . During the off state  334 , the display  18  undergoes three sensing states: active panel conditioning (APC)  336 , emissive element (e.g., OLED) sensing  338 , and TFT sensing  340 . The APC  336 , emissive element sensing  338 , and/or TFT sensing  340  may utilize a common duration (e.g., 10 minutes) or may utilize different durations. 
     In some embodiments, to reduce an overall sensing duration in the off state  334 , the APC  336  and the emissive element sensing  338  may occur with at least some overlap (e.g., may be performed concurrently).  FIG. 16  illustrates a timing diagram  350  that may be used for the display  18 . The timing diagram  350  illustrates that the display  18  may be in an on state  352  and then an off state  354 . During the off state  354 , the display  18  undergoes two sensing states: APC/OLED sensing  356  and TFT sensing  358 . The APC/OLED sensing  356  and the TFT sensing  358  may utilize a common duration (e.g., 10 minutes) or may utilize different durations. 
       FIG. 17  illustrates a schematic diagram  370  illustrating why APC and emissive element sensing may be performed concurrently. The schematic diagram  370  includes an OLED sensing diagram  372 , an APC diagram  374 , and a compound diagram  376 . The OLED sensing diagram  372  illustrates OLED sensing for a pixel  378  by injecting a current  380  into an emissive element  382  (e.g., OLED) from sensing circuitry  19 . The sensing circuitry  19  also detects the voltage across the emissive element  382  to determine aging of the emissive element  382 . 
     The APC diagram  374  illustrates that a signal  384  is injected into the TFT  386  to reduce previous content&#39;s impact to TFT characteristics during the TFT sensing. The APC diagram  374  illustrates that the signal  384  does not induce any current through the emissive element  382  because switch  388  does not allow current to flow through the TFT  386 . Thus, since the signal  384  does not induce current through the emissive element  382  the current  380  may be used to sense the emissive element  382  while signal  384  is used to perform ADC. 
       FIG. 18  illustrates a process  400  that may be used to perform APC and OLED sensing for the display  18  concurrently. The display  18  performs APC (block  402 ). In some embodiments, the APC may be performed by the processor(s) generating the signal  384  and the display applying the signal to TFTs of the display  18 . During the APC, the sensing circuitry  19  senses aging of an emissive element (block  404 ). After APC and emissive element sensing have completed, the sensing circuitry  19  senses TFT aging (block  406 ). 
     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. Furthermore, it should be further understood that each of the embodiments disclosed above may be used with any and all of the other embodiments disclosed herein. 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: 20180831
Publication Date: 20220705
Grant Date: 20220705
Priority Date: 20170925
Inventors: LIN, CHIN-WEI
LIN, HUNG SHENG
KIM, HYUNSOO
NHO, HYUNWOO
HWANG, INJAE
RICHMOND, Jesse A.
RYU, JIE WON
TAN, JUNHUA
MURUGAN, KAVINAATH
BRAHMA, KINGSUK
GAO, SHENGKUI
SHEN, Shiping
CHANG, SUN-IL
CHO, Myung-Je
BI, YAFEI
CHOI, MYUNGJOON
YAO, Weichuan
WANG, CHAOHAO
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2330/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0254", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3208", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2330/021", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/006", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2330/027", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/048", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3406", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3208", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2370/22", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/029", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3208", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/006", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 75908043