PATENT DOCUMENT

Publication Number: US-11688363-B2
Application Number: US-202117376125-A
Country: US
Kind Code: B2

Title: Reference pixel stressing for burn-in compensation systems and methods

Abstract:
An electronic device may include an electronic display including display pixels to display an image based on compensated image data. The electronic display may also include a stressed reference pixel to exhibit burn-in related aging in response to one or more stress sessions and a non-stressed reference pixel configured to not undergo the one or more stress sessions. Additionally, the electronic device may include image processing circuitry to determine a panel-specific aging profile based on a comparison between one or more properties of the stressed reference pixel and the one or more properties of the non-stressed reference pixel. The image processing circuitry may also generate one or more gain maps based on the panel-specific aging profile and generate the compensated image data by applying the one or more gain maps to input image data.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 an electronic display comprising:
 a plurality of display pixels disposed in a display area of the electronic display and configured to display an image based at least in part on compensated image data; 
 a stressed reference pixel disposed outside the display area and configured to exhibit burn-in related aging in response to one or more stress sessions; and 
 a non-stressed reference pixel, separate from the stressed reference pixel, configured to not undergo the one or more stress sessions; and 
 
 image processing circuitry configured to:
 determine a panel-specific aging profile based at least in part on a comparison between one or more properties of the stressed reference pixel and the one or more properties of the non-stressed reference pixel; 
 maintain a burn-in history map corresponding to estimated burn-in ages of the plurality of display pixels; 
 determine a local efficiency map based at least in part on the burn-in history map and the panel-specific aging profile; 
 generate one or more gain maps based at least in part on the local efficiency map; and 
 generate the compensated image data by applying the one or more gain maps to input image data. 
 
 
     
     
       2. The electronic device of  claim 1 , wherein the one or more properties comprises a pixel voltage, wherein the panel-specific aging profile is based at least in part on a voltage difference between the pixel voltage of the stressed reference pixel and the pixel voltage of the non-stressed reference pixel. 
     
     
       3. The electronic device of  claim 1 , wherein the one or more properties comprises a pixel luminance, wherein the panel-specific aging profile is based at least in part on a luminance difference between the pixel luminance of the stressed reference pixel and the pixel luminance of the non-stressed reference pixel. 
     
     
       4. The electronic device of  claim 3 , comprising a plurality of luminance sensors configured to measure the pixel luminance of the stressed reference pixel and the pixel luminance of the non-stressed reference pixel. 
     
     
       5. The electronic device of  claim 1 , wherein the one or more stress sessions comprise enabling the stressed reference pixel to a maximum brightness for one or more respective periods of time such that the burn-in related aging of the stressed reference pixel is greater than a greatest burn-in related age of the plurality of display pixels. 
     
     
       6. The electronic device of  claim 1 , comprising a battery configured to operatively supply power to the electronic device, wherein the one or more stress sessions are configured to occur during charging of the battery. 
     
     
       7. The electronic device of  claim 1 , wherein the electronic display comprises a border that optically hides the stressed reference pixel and the non-stressed reference pixel from view. 
     
     
       8. The electronic device of  claim 1 , comprising drive circuitry dedicated to drive the stressed reference pixel and the non-stressed reference pixel. 
     
     
       9. A method comprising:
 maintaining a burn-in history map associated with burn-in related aging of display pixels of a display panel; 
 stressing a first reference pixel to cause the burn-in related aging to the first reference pixel; 
 measuring a property of the first reference pixel in response to a drive current; 
 measuring the property of a second reference pixel in response to the drive current, wherein the second reference pixel comprises a non-stressed reference pixel separate from the first reference pixel; 
 determining a panel-specific aging profile based on a comparison between the measured property of the first reference pixel and the measured property of the second reference pixel; 
 combining the panel-specific aging profile with the burn-in history map to generate a local luminance map, wherein the local luminance map comprises respective pixel luminance deviations, due to the burn-in related aging, of respective pixels of the display pixels; 
 generating one or more gain maps based at least in part on the local luminance map; and 
 compensating image data for the burn-in related aging of the display pixels based at least in part on the one or more gain maps. 
 
     
     
       10. The method of  claim 9 , wherein the property comprises a pixel voltage. 
     
     
       11. The method of  claim 9 , wherein the property comprises a pixel luminance. 
     
     
       12. The method of  claim 9 , wherein the property of the first reference pixel comprises directly measuring, via one or more luminance sensors, a luminance output of the first reference pixel at the drive current. 
     
     
       13. The method of  claim 12 , comprising:
 changing the drive current to a second drive current; and 
 directly measuring, via the one or more luminance sensors, the luminance output of the first reference pixel at the second drive current. 
 
     
     
       14. The method of  claim 13 , wherein the panel-specific aging profile is based at least in part on the luminance output of the first reference pixel at the drive current and the luminance output of the first reference pixel at the second drive current. 
     
     
       15. Image processing circuitry configured to:
 determine a panel-specific aging profile based at least in part on a voltage difference between a first measured voltage of a first reference pixel and a second measured voltage of a second reference pixel, wherein the first reference pixel has been intentionally stressed to exhibit burn-in related aging, wherein the second reference pixel comprises a non-stressed reference pixel separate from the first reference pixel, wherein the panel-specific aging profile corresponds to a measured efficiency drop of the first reference pixel due at least in part to the burn-in related aging; 
 generate a local efficiency map based at least in part on the panel-specific aging profile and a burn-in history map corresponding to estimated burn-in related aging of a plurality of display pixels configured to display image content based at least in part on image data, wherein the local efficiency map comprises respective pixel efficiency drops, due to the burn-in related aging, of respective pixels of the display pixels; 
 generate one or more gain maps based at least in part on the local efficiency map; and 
 apply the one or more gain maps to the image data to compensate for the estimated burn-in related aging of the display pixels. 
 
     
     
       16. The image processing circuitry of  claim 15 , wherein the image processing circuitry is configured to determine the panel-specific aging profile based on a luminance difference between a first measured luminance of the first reference pixel and a second measured luminance of the second reference pixel. 
     
     
       17. The image processing circuitry of  claim 15 , wherein the panel-specific aging profile is based at least in part on a plurality of voltage differences between the first reference pixel and the second reference pixel in response to a corresponding plurality of driving currents. 
     
     
       18. The image processing circuitry of  claim 15 , wherein the panel-specific aging profile is based at least in part on a plurality of voltage differences between the first reference pixel and the second reference pixel corresponding to a plurality of different stress levels of the first reference pixel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Application No. 63/082,833, entitled “Reference Pixel Stressing for Burn-In Compensation Systems and Methods,” filed Sep. 24, 2020, the disclosure of which is incorporated by reference in its entirety for all purposes. 
    
    
     SUMMARY 
     This disclosure relates to image data processing and compensating for pixel burn-in/aging of pixels of an electronic display. 
     Numerous electronic devices—including televisions, portable phones, computers, wearable devices, vehicle dashboards, virtual-reality glasses, and more—display images on an electronic display. As electronic displays gain increasingly higher resolutions and dynamic ranges, they may also become increasingly more susceptible to image display artifacts due to pixel burn-in. This disclosure relates to identifying and compensating for burn-in and/or aging artifacts on an electronic display. Burn-in is a phenomenon whereby pixels degrade over time owing to various factors, including the different amounts of light that different pixels may emit over time. For example, if certain pixels are used more frequently than others, or used in situations that are more likely cause undue aging, such as high temperature environments, those pixels may exhibit more aging than other pixels. As a result, those pixels may gradually emit less light when given the same driving current or voltage values, effectively becoming darker than other pixels when given a signal for the same brightness level. As such, without compensation, burn-in artifacts may be visibly perceived due to non-uniform sub-pixel aging. 
     In some embodiments, circuitry and/or software may monitor or model a burn-in effect that would be likely to occur in the electronic display as a result of the image data that is sent to the electronic display. For example, statistics surrounding the utilization of the pixels of the electronic display and/or environmental conditions (e.g., temperature) during operation of the pixels may be analyzed and tracked (e.g., via a burn-in history map). The statistics may then be used to derive gain maps for adjusting image data before it is sent to the electronic display to reduce or eliminate the appearance of burn-in artifacts on the electronic display. 
     However, the pixels of different display panels may exhibit different aging rates due to environmental factors, manufacturing tolerances, case-specific utilization, etc. As such, embodiments of the present disclosure include reference pixels that may be stressed during the life of the electronic display to generate a panel-specific aging profile. The reference pixels may be stressed and voltage shift measured to determine the panel-specific aging profile. The panel-specific aging profile may correlate burn-in related aging to pixel efficiency drop and changes in luminance output that is specific to the individual electronic display. By using a panel-specific aging profile, the electronic display may have reduced perceivable artifacts and/or may have increased peak brightness capabilities. 
     Additionally or alternatively, the electronic device may stress the reference pixels and measure the luminance output of the reference pixels via a luminance sensor (e.g., photodiode, photoresistor, etc.). The measured luminance output of the reference pixels may provide data to generate a panel-specific luminance profile which may be used instead of, in conjunction with, or as part of the panel-specific aging profile. For example, the luminance output of the reference pixels stressed during the life of the electronic display may be measured at given image data values to give valuable insight into the how pixels of the particular panel age over time and through operation. 
     Burn-in gain maps may be derived to compensate for the burn-in effects based on the tracked operation of the active area pixels using the panel-specific aging profile. In this way, the pixels of the electronic display that have suffered the greatest amount of aging will appear to be equally as bright as the pixels that have suffered the least amount of aging. As such, perceivable burn-in artifacts on the electronic display may be reduced or eliminated. 
     Various refinements of the features noted above may exist in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG.  1    is a block diagram of an electronic device including an electronic display, in accordance with an embodiment; 
         FIG.  2    is an example of the electronic device of  FIG.  1   , in accordance with an embodiment; 
         FIG.  3    is another example of the electronic device of  FIG.  1   , in accordance with an embodiment; 
         FIG.  4    is another example of the electronic device of  FIG.  1   , in accordance with an embodiment; 
         FIG.  5    is another example of the electronic device of  FIG.  1   , in accordance with an embodiment; 
         FIG.  6    is a block diagram of a portion of the electronic device of  FIG.  1    including a display pipeline having a burn-in compensation (BIC) and burn-in statistics (BIS) collection block, in accordance with an embodiment; 
         FIG.  7    is a flowchart of an example process for operating the display pipeline of  FIG.  6   , in accordance with an embodiment; 
         FIG.  8    is a block diagram of the burn-in compensation (BIC) and burn-in statistics (BIS) collection block of  FIG.  6   , in accordance with an embodiment; 
         FIG.  9    is a diagrammatic representation of a display panel having reference pixels, in accordance with an embodiment; 
         FIG.  10    is a graph of example driving currents and pixel voltages, in accordance with an embodiment; 
         FIG.  11    is a graph of example pixel efficiency and burn-in age, in accordance with an embodiment; 
         FIG.  12    is a flow diagram of an example process using a panel-specific aging profile to determine compensated pixel values, in accordance with an embodiment; and 
         FIG.  13    is a flowchart of an example process for compensating input pixel values for potential burn-in related aging effects, in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but may nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding 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. 
     Numerous electronic devices—including televisions, portable phones, computers, wearable devices, vehicle dashboards, virtual-reality glasses, and more—display images on an electronic display. As electronic displays gain increasingly higher resolutions and dynamic ranges, they may also become increasingly more susceptible to image display artifacts due to pixel burn-in. Burn-in is a phenomenon whereby pixels degrade over time owing to the different amount of light that different pixels emit over time. In other words, pixels may age at different rates depending on their relative utilization. For example, pixels used more than others may age more quickly, and thus may gradually emit less light when given the same amount of driving current or voltage. This may produce undesirable burn-in image artifacts on the electronic display. 
     Circuitry and/or software may monitor or model a burn-in effect that would be likely to occur in the electronic display as a result of the image data that is sent to the electronic display. For example, statistics surrounding the utilization of the pixels of the electronic display and/or environmental conditions (e.g., temperature) during operation of the pixels may be analyzed and tracked (e.g., via a burn-in history map) and used to derive gain maps for adjusting image data, before it is sent to the electronic display, to reduce or eliminate the appearance of burn-in artifacts on the electronic display. However, the pixels of different display panels may exhibit different aging rates due to environmental factors, manufacturing tolerances, case-specific utilization, etc. As such, to improve compensation accuracy, embodiments of the present disclosure include reference pixels that may be stressed and monitored during the life of the electronic display to generate a panel-specific aging profile. 
     In some embodiments, the reference pixels may be stressed and voltage shift measured to determine the panel-specific aging profile. The panel-specific aging profile may correlate burn-in related aging to a pixel efficiency drop and a change in luminance output that is specific to the individual electronic display. By using a panel-specific aging profile, the electronic display may have reduced perceivable artifacts and/or may have increased peak brightness capabilities. 
     Additionally or alternatively, the electronic device may stress the reference pixels and measure the luminance output of the reference pixels via a luminance sensor such as a photodiode, photoresistor, or other luminance measuring technique. The measured luminance output of the reference pixels may provide data to generate a panel-specific luminance profile which may be used instead of, in conjunction with, or as part of the panel-specific aging profile. For example, the luminance output of the reference pixels stressed during the life of the electronic display may be measured at given image data values to give valuable insight into the how pixels of the particular panel age over time and through operation. 
     Burn-in gain maps may be derived based on the tracked operation of the active area pixels and the panel-specific aging profile to compensate image data for the burn-in effects. In this way, the pixels of the electronic display that have suffered the greatest amount of aging will appear to be equally as bright as the pixels that have suffered the least amount of aging. As such, perceivable burn-in artifacts on the electronic display may be reduced or eliminated. 
     To help illustrate, one embodiment of an electronic device  10  that utilizes an electronic display  12  is shown in  FIG.  1   . As will be described in more detail below, the electronic device  10  may be any suitable electronic device, such as a handheld electronic device, a tablet electronic device, a notebook computer, and the like. Thus, it should be noted that  FIG.  1    is merely one example of a particular implementation and is intended to illustrate the types of components that may be present in the electronic device  10 . 
     The electronic device  10  may include one or more electronic displays  12 , input devices  14 , input/output (I/O) ports  16 , a processor core complex  18  having one or more processors or processor cores, local memory  20 , a main memory storage device  22 , a network interface  24 , a power source  26 , and image processing circuitry  28 . The various components described in  FIG.  1    may include hardware elements (e.g., circuitry), software elements (e.g., a tangible, non-transitory computer-readable medium storing instructions), or a combination of both hardware and software elements. As should be appreciated, the various components may be combined into fewer components or separated into additional components. For example, the local memory  20  and the main memory storage device  22  may be included in a single component. Additionally, the image processing circuitry  28  (e.g., a graphics processing unit, a display image processing pipeline, etc.) may be included in the processor core complex  18 . 
     The processor core complex  18  may be operably coupled with local memory  20  and the main memory storage device  22 . The local memory  20  and/or the main memory storage device  22  may include tangible, non-transitory, computer-readable media that store instructions executable by the processor core complex  18  and/or data to be processed by the processor core complex  18 . For example, the local memory  20  may include random access memory (RAM) and the main memory storage device  22  may include read only memory (ROM), rewritable non-volatile memory such as flash memory, hard drives, optical discs, and/or the like. 
     The processor core complex  18  may execute instructions stored in local memory  20  and/or the main memory storage device  22  to perform operations, such as generating source image data. As such, the processor core complex  18  may include one or more general purpose microprocessors, one or more application specific processors (ASICs), one or more field programmable logic arrays (FPGAs), or any combination thereof. 
     The network interface  24  may connect the electronic device  10  to a personal area network (PAN), such as a Bluetooth network, a local area network (LAN), such as an 802.11x Wi-Fi network, and/or a wide area network (WAN), such as a 4G or LTE cellular network. In this manner, the network interface  24  may enable the electronic device  10  to transmit image data to a network and/or receive image data from the network. 
     The power source  26  may provide electrical power to operate the processor core complex  18  and/or other components in the electronic device  10 . Thus, the power source  26  may include any suitable source of energy, such as a rechargeable lithium polymer (Li-poly) battery and/or an alternating current (AC) power converter. 
     The I/O ports  16  may enable the electronic device  10  to interface with various other electronic devices. The input devices  14  may enable a user to interact with the electronic device  10 . For example, the input devices  14  may include buttons, keyboards, mice, trackpads, and the like. Additionally or alternatively, the electronic display  12  may include touch sensing components that enable user inputs to the electronic device  10  by detecting occurrence and/or position of an object touching its screen (e.g., surface of the electronic display  12 ). 
     The electronic display  12  may display a graphical user interface (GUI) of an operating system, an application interface, text, a still image, or video content. To facilitate displaying images, the electronic display  12  may include a display panel with one or more display pixels. Additionally, each display pixel may include one or more sub-pixels, which each control the luminance of a color component (e.g., red, green, or blue). As used herein, a display pixel may refer to a collection of sub-pixels (e.g., red, green, and blue subpixels) or may refer to a single sub-pixel. 
     As described above, the electronic display  12  may display an image by controlling the luminance of the sub-pixels based at least in part on corresponding image data. In some embodiments, the image data may be received from another electronic device, for example, via the network interface  24  and/or the I/O ports  16 . Additionally or alternatively, the image data may be generated by the processor core complex  18  and/or the image processing circuitry  28 . Moreover, in some embodiments, the electronic device  10  may include multiple electronic displays  12  and/or may perform image processing (e.g., via the image processing circuitry  28 ) for one or more external electronic displays  12 , such as connected via the network interface  24  and/or the I/O ports  16 . 
     The electronic device  10  may be any suitable electronic device. To help illustrate, one example of a suitable electronic device  10 , specifically a handheld device  10 A, is shown in  FIG.  2   . In some embodiments, the handheld device  10 A may be a portable phone, a media player, a personal data organizer, a handheld game platform, and/or the like. For example, the handheld device  10 A may be a smart phone, such as any iPhone® model available from Apple Inc. 
     The handheld device  10 A may include an enclosure  30  (e.g., housing) to, for example, protect interior components from physical damage and/or shield them from electromagnetic interference. Additionally, the enclosure  30  may surround, at least partially, the electronic display  12 . In the depicted embodiment, the electronic display  12  is displaying a graphical user interface (GUI)  32  having an array of icons  34 . By way of example, when an icon  34  is selected either by an input device  14  or a touch-sensing component of the electronic display  12 , an application program may launch. 
     Furthermore, input devices  14  may be provided through openings in the enclosure  30 . As described above, the input devices  14  may enable a user to interact with the handheld device  10 A. For example, the input devices  14  may enable the user to activate or deactivate the handheld device  10 A, navigate a user interface to a home screen, navigate a user interface to a user-configurable application screen, activate a voice-recognition feature, provide volume control, and/or toggle between vibrate and ring modes. Moreover, the I/O ports  16  may also open through the enclosure  30 . 
     Another example of a suitable electronic device  10 , specifically a tablet device  10 B, is shown in  FIG.  3   . For illustrative purposes, the tablet device  10 B may be any iPad® model available from Apple Inc. A further example of a suitable electronic device  10 , specifically a computer  10 C, is shown in  FIG.  4   . For illustrative purposes, the computer  10 C may be any MacBook® or iMac® model available from Apple Inc. Another example of a suitable electronic device  10 , specifically a watch  10 D, is shown in  FIG.  5   . For illustrative purposes, the watch  10 D may be any Apple Watch® model available from Apple Inc. As depicted, the tablet device  10 B, the computer  10 C, and the watch  10 D each also includes an electronic display  12 , input devices  14 , I/O ports  16 , and an enclosure  30 . 
     The electronic display  12  may display images based at least in part on image data. Before being used to display a corresponding image on the electronic display  12 , the image data may be processed, for example, via the image processing circuitry  28 . The image processing circuitry  28  may include a display pipeline, memory-to-memory scaler and rotator (MSR) circuitry, or additional hardware or software for processing image data. As should be appreciated, the present techniques may be implemented in standalone circuitry, software, and/or firmware. 
     As described above, the image data may be processed to compensate for an estimated amount of burn-in related aging to reduce or eliminate perceivable artifacts due to pixel aging. To help illustrate, a portion of the electronic device  10 , including a display pipeline  36 , is shown in  FIG.  6   . In some embodiments, the display pipeline  36  may be implemented by circuitry in the electronic device  10 , circuitry in the electronic display  12 , or a combination thereof. For example, the display pipeline  36  may be included in the processor core complex  18 , the image processing circuitry  28 , a timing controller (TCON) in the electronic display  12 , or any combination thereof. As should be appreciated, although image processing is discussed herein as being performed via the display pipeline  36 , embodiments may include hardware, software, or firmware components that carry out the present techniques as part of, separate from, and/or parallel with a display pipeline, MSR circuitry, or other image processing circuitry. 
     The electronic device  10  may also include an image data source  38 , a display panel  40 , and/or a controller  42  in communication with the display pipeline  36 . In some embodiments, the display panel  40  of the electronic display  12  may be a liquid crystal display (LCD), a light emitting diode (LED) display, an organic LED (OLED) display, or any other suitable type of display panel  40 . In some embodiments, the controller  42  may control operation of the display pipeline  36 , the image data source  38 , and/or the display panel  40 . To facilitate controlling operation, the controller  42  may include a controller processor  44  and/or controller memory  46 . In some embodiments, the controller processor  44  may be included in the processor core complex  18 , the image processing circuitry  28 , a timing controller in the electronic display  12 , a separate processing module, or any combination thereof and execute instructions stored in the controller memory  46 . Additionally, in some embodiments, the controller memory  46  may be included in the local memory  20 , the main memory storage device  22 , a separate tangible, non-transitory, computer readable medium, or any combination thereof. 
     The display pipeline  36  may receive source image data  48  corresponding to a desired image to be displayed on the electronic display  12  from the image data source  38 . The source image data  48  may indicate target characteristics (e.g., pixel data) corresponding to the desired image using any suitable source format, such as an 8-bit fixed point αRGB format, a 10-bit fixed point αRGB format, a signed 16-bit floating point αRGB format, an 8-bit fixed point YCbCr format, a 10-bit fixed point YCbCr format, a 12-bit fixed point YCbCr format, and/or the like. In some embodiments, the image data source  38  may include the processor core complex  18 , the image processing circuitry  28 , memory  20 , a storage device  22 , the network interface  24 , I/O ports  16 , or a combination thereof. Furthermore, the source image data  48  may reside in a linear color space, a gamma-corrected color space, or any other suitable color space. As used herein, pixels or pixel data may refer to a grouping of sub-pixels (e.g., individual color component pixels such as red, green, and blue) or the sub-pixels themselves. 
     As described above, the display pipeline  36  may operate to process source image data  48  received from the image data source  38 . The display pipeline  36  may include one or more image data processing blocks (e.g., circuitry, modules, or processing stages) such as a burn-in compensation (BIC)/burn-in statistics (BIS) block  50 . As should be appreciated, multiple other image data processing blocks may also be incorporated into the display pipeline  36  such as a color management block, a dither block, etc. Further, the functions (e.g., operations) performed by the display pipeline  36  may be divided between various image data processing blocks, and while the term “block” is used herein, there may or may not be a logical separation between the image data processing blocks. 
     The BIC/BIS block  50  may compensate for burn-in to reduce or eliminate the visual effects of burn-in, as well as to collect image statistics about the degree to which burn-in is expected to have occurred on the electronic display  12 . As such, the BIC/BIS block  50  may receive input pixel values  52  representative of each of the color components of the source image data  48  and output compensated pixel values  54 . As stated above, other image data processing blocks may also be utilized in the display pipeline  36 . As such, the input pixel values  52  and/or the compensated pixel values  54  may be processed by other image data processing blocks before and/or after the BIC/BIS block  50 . By including the BIC/BIS block  50  in image processing, the resulting display image data  56  output by the display pipeline  36  for display on the display panel  40  may suffer substantially fewer or no burn-in artifacts. After processing, the display pipeline  36  may output the display image data  56  to the display panel  40 . Based at least in part on the display image data  56 , the display panel  40  may apply analog electrical signals to the display pixels of the electronic display  12  to display one or more corresponding images. 
     To help illustrate,  FIG.  7    is a flowchart  58  of an example process for operating the display pipeline  36 . Generally, the process of the flowchart  58  may include receiving source image data  48  from the image data source  38  or from another portion of the image processing circuitry  28  (process block  60 ). The display pipeline may also perform burn-in compensation (BIC) and/or collect burn-in statistics (BIS) (process block  62 ), for example, via the BIC/BIS block  50 . The display pipeline may then output the display image data  56 , which is compensated for burn-in effects (process block  64 ). In some embodiments, the process of the flowchart  58  may be implemented based on circuit connections formed in the display pipeline  36 . Additionally or alternatively, in some embodiments, the process of the flowchart  58  may be implemented in whole or in part by executing instructions stored in a tangible non-transitory computer-readable medium, such as the controller memory  46 , using processing circuitry, such as the controller processor  44 . 
     The BIC/BIS block  50  may encompass a BIC sub-block  74  and a BIS collection sub-block  76 , as shown in  FIG.  8   . The BIC sub-block  74  may receive the input pixel values  52  and output the compensated pixel values  54  adjusted for non-uniform pixel aging of the electronic display  12 . Additionally, the BIS collection sub-block  76  may analyze all or a portion of the compensated pixel values  54  to generate a BIS history update  78  (i.e., an incremental update) representing an increased amount of pixel aging that is estimated to have occurred since a corresponding previous BIS history update  78 . In some embodiments, a burn-in history map  80  may maintained as a cumulative mapping of the estimated burn-in related aging of the display panel  40 . 
     Additionally, a panel-specific aging profile  82  may be maintained to correlate the burn-in history map  80  to changes in luminance for the pixels of the display panel  40 . The BIC/BIS block  50  may use the burn-in history map  80  and the panel-specific aging profile  82  in a compute gain maps sub-block  84  to generate gain maps  86  for compensating the input pixel values  52 . In some embodiments, the gain maps  86  may be two-dimensional (2D) maps of per-color-component pixel gains. For example, the gain maps  86  may be programmed into 2D lookup tables (LUTs) in the display pipeline  36  for use by the BIC sub-block  74 . 
     Additionally, in some embodiments, the BIC sub-block  74  may utilize gain parameters  88  to account for dynamic and/or global (e.g., affecting the entire, majority, or preset portions of display pixels) factors such as brightness settings, normalizations, etc. As should be appreciated, the gain parameters  88  are non-limiting and additional parameters may also be included in determining the compensated pixel values  54  such as floating or fixed reference values and/or parameters representative of the type of electronic display panel  40 . As such, the gain parameters  88  may represent any suitable parameters that the BIC sub-block  74  may use to appropriately adjust the values of and/or apply the gain maps  86  to compensate for burn-in. 
     As discussed above, the burn-in compensation processing  74  may utilize a panel-specific aging profile  82  to help determine the compensations to the input pixel values  52 . In order to generate the panel-specific aging profile  82 , the display panel  40  may include one or more reference pixels  90  in addition to the pixels within the active area  92 , as shown in  FIG.  9   . In some embodiments, the reference pixels  90  may be physically, logically, and/or electrically equivalent to pixels within the active area  92  of the display panel  40  to more accurately predict pixel aging for the pixels within the active area  92 . The active area  92  may generally correspond to the portion of the electronic display  12  that operationally displays content based on the compensated pixel values  54  and/or is visible to a user. 
     In order to generate reference data indicative of how the pixels of the display panel  40  exhibit burn-in, some of the reference pixels  90  may be intentionally aged (e.g., subjected to burn-in stress) by activation at known luminance output levels (e.g., 25 percent luminance output, 50 percent luminance output, 75 percent luminance output, or 100 percent luminance output). As such, stressed reference pixels  90 A may exhibit electrical characteristics of burn-in related aging as well as reduced luminance output as the stressed reference pixels  90 A are stressed more and more during the life of the display panel  40 . For comparison, non-stressed reference pixels  90 B may be left off or undergo very little activation during the life of the display panel  40 . During sensing, a comparison may be made between the stressed reference pixels  90 A and the non-stressed reference pixels  90 B. Any suitable number of reference pixels  90  may be used to determine the panel-specific aging profile  82 . For example, the display panel  40  may include 10, 100, 200, 300, 1000, or more reference pixels  90 . As should be understood, each reference pixel  90  may include multiple sub-pixels (e.g., a red sub-pixel, a green sub-pixel, and a blue sub-pixel). Moreover, although discussed herein as relating to pixels, the profiles and mappings of the present disclosure may include sub-profiles or sub-mappings, respectively, for each color component and may be applied on a sub-pixel basis. In some embodiments, the stressed reference pixels  90 A and non-stressed reference pixels  90 B may alternate along a row of reference pixels  90  or be patterned/grouped. Furthermore, in some embodiments, each of the stressed reference pixels  90 A may be stressed the same amount or stressed differently in groups. For example, groups of stressed reference pixels  90 A may be stressed at different rates to maintain reference data points at lower burn-in related age levels as the temporal age of the display panel  40  increases. 
     As discussed herein, stressing and/or sensing (e.g., for measuring burn-in) of the reference pixels  90  may occur during the life of the display panel  40 . In some embodiments, the stressed reference pixels  90 A may be stressed during one or more stress sessions periodically and/or in response to certain conditions. For example, a stress session may be initiated (e.g., via the BIC/BIS block  50 ) to maintain at least a portion of the stressed reference pixels  90 A as aged as the most aged pixel of the active area  92 . As such, the panel-specific aging profile  82  may be applicable for each pixel of the active area  92 . However, if pixels of the active area  92  do exceed the burn-in age of the stressed reference pixels  90 A, a predefined aging profile or estimated extension of the panel-specific aging profile  82  may be used. Further, for electronic devices  10  utilizing a battery, stressing and/or sensing of the reference pixels  90 A may take place while the electronic device  10  is connected to external power (e.g., during charging), to avoid impacts on power consumption. As should be appreciated different modes of operation of the electronic device  10  may enable or disable stressing and sensing of the reference pixels  90 . 
     Additionally, during stressing and/or sensing, the reference pixels  90  may emit light that does not correspond to a desired image to be displayed. As such, in some embodiments, the reference pixels  90  may be hidden from view. For example, the reference pixels  90  may be disposed behind/beneath a border  94  (e.g., mask) of the electronic display  12  and/or disposed internal to the enclosure  30  such that the emitted light is not visible outside of the enclosure  30 . 
     The reference pixels  90  may be driven by drive circuitry  96 , which may be standalone circuitry or implemented as part of the drive circuitry for pixels of the active area  92 . Furthermore, sense circuitry  98  may measure the electrical properties of the reference pixels  90  during sensing to help determine how the stressed reference pixels  90 A have aged in response to the applied stresses. Additionally or alternatively to the sense circuitry  98 , and as discussed further below, the burn-in related aging of the reference pixels  90  may also be measured by luminance sensors  100 , such as photoresistors, photodiodes, etc., controlled via photosense circuitry  102 . In some embodiments, the luminance sensors  100  may be alternatingly disposed on different sides of the reference pixels  90 , for example, for spacing and/or to assist in optical isolation between referenced pixels  90  being sensed. 
     After stressing the stressed reference pixels  90 A, sensing of the reference pixels  90  may be accomplished by driving the stressed reference pixels  90 A and the non-stressed reference pixels  90 B and measuring their respective responses. For example,  FIG.  10    is a graph  104  of drive currents  106  on the y-axis and pixel voltages  108  on the x-axis. In some embodiments, the drive circuitry  96  may provide drive currents  106  to each of the reference pixels  90  at multiple levels (e.g., Ii,  12 , and  13 ) and the pixel voltages  108  may be measured for each of the stressed reference pixels  90 A and the non-stressed reference pixels  90 B. As the drive current  106  is increased (e.g., in steps or continuously), a stressed curve  110  and a non-stressed curve  112  may be determined. Any suitable number of drive current  106  steps may be used (e.g., 3 steps, 10 steps, 20 steps, 100, steps, etc.) depending on desired granularity and implementation factors. In some embodiments, the pixel voltages  108  of the stressed curve  110  and the non-stressed curve  112  may be calculated as averages, medians, or other measures characteristic of the majority of the stressed reference pixels  90 A and the non-stressed reference pixels  90 B, respectively. 
     The voltage difference  114  (e.g., ΔV 1 , ΔV 2 , and ΔV 3 ) between the stressed curve  110  and the non-stressed curve  112  may correspond to an efficiency drop of the stressed reference pixels  90 A associated with their burn-in related age due to the stressing. By stressing the stressed reference pixels  90 A to different burn-in ages and measuring the voltage differences  114 , the efficiency of the stressed reference pixels  90 A may be determined as a function of the burn-in age.  FIG.  11    is a graph  116  of the normalized pixel efficiency  118 , on the y-axis, and the burn-in age  120 , on the x-axis. A reference pixel curve  122  may illustrate the determined pixel efficiencies  118  of the stressed reference pixels  90 A based on the measured voltage differences  114  at different burn-in ages  120  (e.g., as stressed over the life of the display panel  40 ). Because the reference pixels  90  may be representative of the pixels of the display panel  40 , the reference pixel curve  122 , or other data structure based on the measured voltage differences  114 , may represent the panel-specific aging profile  82 . Further, combining the panel-specific aging profile  82  with the burn-in history map  80  may generate profiles for other pixels, for example, as illustrated by pixel  1  curve  124  and pixel  2  curve  126 . The reference pixel curve  122  has a panel efficiency drop  128  for a given burn-in age  120 . Likewise, other pixels may have local efficiency drops  130  relative to the panel efficiency drop  128  due to factors local to those specific pixels such as local temperature during pixel operation and average pixel luminance during pixel operation. 
     To help further illustrate,  FIG.  12    is a flow diagram  132  of how the panel-specific aging profile  82 , generated based on the measured voltage responses of the reference pixels  90 , may be used to determine the compensated pixel values  54 . For example, the panel-specific aging profile  82  may be combined with the burn-in history map  80 , maintained based on BIS history updates  78  of pixels within the active area  92 , to generate the local efficiency map  134 . The local efficiency map  134  may correspond to the local efficiency drops  130  for the pixels of the entire active area  92 . The local efficiency map  134  may be used to generate one or more gain maps  86  that may be combined with the input pixel values  52  to generate the compensated pixel values  54 . 
     Returning to  FIG.  9   , additionally or alternatively to the sense circuitry  98 , the burn-in related aging of the reference pixels  90  may also be measured by luminance sensors  100 , such as photoresistors (e.g., thin-film transistors without gates), photodiodes, etc., controlled via photosense circuitry  102 . For example, during sensing, the drive currents  106  may be applied to the reference pixels  90  and the reference pixels  90  emit light corresponding thereto. The luminance sensors  100  may sense the luminance output of the reference pixels  90 , and a voltage indicative thereof may be measured via the photosense circuitry  102 . 
     Similar to the graph  104  where the voltage differences  114  between the stressed curve  110  and the non-stressed curve  112  are determined, the luminance differences between the stressed reference pixels  90 A and the non-stressed reference pixels  90 B may be indicative of the burn-in related aging of the stressed reference pixels  90 A. In some embodiments, the luminance differences between the stressed reference pixels  90 A and the non-stressed reference pixels  90 B may be used to generate a panel-specific luminance profile, which, when combined with the burn-in history map  80  may be used to generate a local luminance map. The local luminance map may represent the deviations in luminance for pixels of the active area  92  due to burn-in related aging for given applied signals. As such, gain maps  86  may be generated to compensate the input pixel values  52  for the deviations in luminance. 
     The local luminance map may be used in conjunction with or instead of the local efficiency map  134 . Moreover, in some embodiments, the panel-specific luminance profile may be combined with or supplant the panel-specific aging profile  82 , such that the local efficiency map  134  is based, at least in part, on the panel-specific luminance profile. For example, the panel-specific luminance profile and the panel-specific aging profile  82  may be averaged to form a panel-specific combined profile used to generate the local efficiency map  134 . 
       FIG.  13    is a flowchart  136  of an example process for compensating input pixel values  52  for potential burn-in related aging effects. The BIC/BIS block  50  may maintain a burn-in history map  80  indicative of burn-in related aging of pixels in the active area  92  of a display panel  40  (process block  138 ). As should be appreciated, the burn-in history map  80  may be continuously updated throughout the life of the display panel  40  in response to pixel usage. Additionally, reference pixels  90  may be maintained and analyzed to determine panel-specific aging of the pixels of the active area  92 . For example, some reference pixels  90  (e.g., stressed reference pixels  90 A) may be stressed to cause burn-in related aging to the stressed reference pixels  90 A (process block  140 ). The properties of the stressed reference pixels  90 A may then be measured (process block  142 ). As should be appreciated, multiple measurements may be taken at various stress levels (e.g., burn-in related ages) of the stressed reference pixels  90 A. 
     Measuring the properties of the stressed reference pixels  90 A may include measuring voltage differences  114  between stressed reference pixels  90 A and non-stressed reference pixels  90 B (process block  144 ), for example, in response to multiple different driving currents  106 . Additionally or alternatively, measuring the properties of the stressed reference pixels  90 A may include measuring luminance differences between stressed reference pixels  90 A and non-stressed reference pixels  90 B (process block  146 ), for example, in response to multiple different driving currents  106 . The measured voltage differences  114  may be used to determine a panel-specific aging profile  82  (process block  148 ). Similarly, the measured luminance differences may be used to determine a panel-specific luminance profile (process block  150 ). The panel-specific aging profile  82  and/or the panel-specific luminance profile may be combined with the burn-in history map  80  to generate a local efficiency map  134  and/or a local luminance map (process block  152 ). In some embodiments, the panel-specific aging profile  82  and the panel-specific luminance profile may be merged and used to generate the local efficiency map  134 . Further, in some embodiments, the local luminance map may be generated based on the panel-specific luminance profile and used in conjunction with or merged with the local efficiency map  134 . Gain maps  86  may be generated based on the local efficiency map  134  and/or the local luminance map (process block  154 ), and the input pixel values  52  may be compensated, via the gain maps  86 , to generate the compensated pixel values  54  (process block  156 ). 
     By compiling and storing the burn-in history map  80  and augmenting it using the panel-specific aging profile  82  and/or the panel-specific luminance profile, gain maps  86  may be determined that counteract the effects of the non-uniform pixel aging. By applying the gains of the gain maps  86  to the input pixel values  52  before they are provided to the electronic display  12 , burn-in artifacts that might have otherwise appeared on the electronic display  12  may be reduced or eliminated in advance. Thereby, the burn-in compensation of this disclosure may provide a vastly improved user experience while efficiently using resources of the electronic device  10 . 
     Although the above referenced flowcharts  58  and  136  are shown in a given order, in certain embodiments, process blocks may be reordered, altered, merged, deleted, and/or occur simultaneously. Additionally, the referenced flowcharts  58  and  136  are given as illustrative tools and further decision and process blocks may also be added depending on implementation. 
     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: 20210714
Publication Date: 20230627
Grant Date: 20230627
Priority Date: 20200924
Inventors: YANG, MAOFENG
JIN, JIAYI
DOYLE, DAVID A.
ZHANG, YIFAN
YAO, WEIJUN
LEE, JIYE
KOH, TAE-WOOK
MATHAI, MATHEW K.
QIAN, Chuang
TSAI, TSUNG-TING
LANDRY, JAMES P.
PILLAI, Kiran S.
HWANG, INJAE
LI, YONGJUN
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2320/046", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/145", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2330/028", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/2092", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/046", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/043", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/029", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/145", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/145", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2330/028", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/046", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 80739394