In-Pixel Compensation for Current Droop and In-Pixel Compensation Timing

An electronic device may include an electronic display including display pixels to display an image based on compensated image data. As image data is written to a pixel in the row of pixels, capacitive coupling at a driver may lead to distortion on the driver. In particular, the capacitive coupling may cause distortion at a storage capacitor, which may lead to current droop at the pixel. The current droop may be reduced or eliminated in each pixel by performing pixel compensation. The pattern of the pixel compensation may be selected such that, over a number of subframes, an average amount of light is the same or similar to what would be emitted had pixel compensation been performed on each pixel in each subframe.

SUMMARY

This disclosure relates to compensating for pixel distortion to prevent undesirable image artifacts on an electronic display of an electronic device.

Numerous electronic devices—including televisions, portable phones, computers, wearable devices, vehicle dashboards, virtual-reality glasses, and more—display images on an electronic display. Electronic displays with self-emissive display pixels produce their own light. Self-emissive display pixels may include any suitable light-emissive elements, including light-emitting diodes (LEDs) such as organic light-emitting diodes (OLEDs) or micro-light-emitting diodes (μLEDs). By causing different display pixels to emit different amounts of light, individual display pixels of an electronic display may collectively produce images.

In certain electronic displays (e.g., a μLEDs display), a microdriver may drive a row of pixels in succession over a period of time. As subsequent pixels in the row are driven, inherent electrical resistance in the pixels and conductors coupling the pixels may cause a current droop or a current rise in the subsequent pixels in the row. Consequently, each subsequent pixel may emit less light than the prior pixel. The current droop may produce various visible image artifacts (e.g., banding) on the electronic display. The artifacts may be exacerbated by a touch sensor subsystem.

Additionally, as image data is written to a pixel (e.g., via the microdriver) in the row of pixels, capacitive coupling at the microdriver may lead to distortion on the microdriver. In particular, the capacitive coupling may cause distortion at a storage capacitor, which may lead to current droop or current rise at the pixel. Moreover, the distortion may increase at each subsequent pixel in the row of pixels, which may lead to greater distortion, and consequently greater current droop or current rise on the pixels, with pixels in the last row of the pixels experiencing the greatest current droop or the greatest current rise. As a result of the increasing current droop or the increasing current rise, the pixels further along the row may emit less light than the prior pixel. The current droop or rise may produce various visible image artifacts (e.g., banding) on the electronic display.

In an embodiment, the current droop or rise may be reduced or eliminated in each pixel by performing pixel compensation. Pixel compensation (e.g., which may, in some cases, be referred to as in-pixel compensation (IPC)), may include refreshing a storage capacitor by updating the storage voltage on the storage capacitor. In this way, pixel compensation may reduce or eliminate the distortion experienced at the microdriver for a period of time caused by the current droop or the current rise. While using pixel compensation may reduce or eliminate current droop or current rise each time it is performed, performing pixel compensation on each pixel in the electronic display may result in excessive power consumption.

In another embodiment, pixel compensation may be performed on different pixels in a row of pixels for different subframes to prevent adjacent pixels of the row from consistently emitting less light than the prior pixel of the row. The pattern of the pixel compensation may be selected such that, over a number of subframes, an average amount of light is the same or similar to what would be emitted had pixel compensation been performed on each pixel in each subframe. For example, pixel compensation may be performed on every third pixel of the row in a first subframe, and then the pixels on which pixel compensation may be performed may be shifted by a number of pixels in the row. In another example the pixel compensation may be performed on every seventh pixel of a row of eight pixels, such that the first pixel of the row and the eighth pixel are corrected via pixel compensation in a first subframe, the seventh pixel is corrected in a second subframe, the sixth pixel is corrected in a third subframe, and so on. The aforementioned shuffling pattern and/or other shuffling patterns may further reduce an appearance of image artifacts by taking into account an intra-frame pause during a touch sensor operation. While performing pixel compensation may be discussed as reducing or eliminating current droop, it should be noted that the same principles may apply to reducing or eliminating current rise.

DETAILED DESCRIPTION

As image data is written to a pixel (e.g., via a microdriver) in a row of pixels, capacitive coupling at the microdriver may lead to distortion on the microdriver. In particular, the capacitive coupling may cause distortion at a storage capacitor, which may lead to current droop at the pixel. Moreover, the distortion may increase over time such that distortion grows at each subsequent pixel in the row of pixels, which may lead to greater distortion, and consequently greater current droop on the pixels, with pixels in the last row of the pixels experiencing the greatest current droop. As a result of the increasing current droop, the pixels further along the row may emit less light than the prior pixel. Consistent current droop across rows may produce various visible image artifacts (e.g., banding) on the electronic display.

In an embodiment, the current droop may be reduced or eliminated in each pixel by performing pixel compensation. Pixel compensation, as defined herein, may be performed at the microdriver include refreshing a storage capacitor by updating the storage voltage on the storage capacitor. In this way, pixel compensation may reduce or eliminate the distortion experienced at the microdriver for a period of time. While using pixel compensation may reduce or eliminate current droop, performing pixel compensation on each pixel in the electronic display may result in excessive power consumption.

In another embodiment, pixel compensation may be performed on different pixels in a row of pixels for different subframes to prevent adjacent pixels of the row from consistently emitting less light than the prior pixel of the row. The pattern of the pixel compensation may be selected such that, over a number of subframes, an average amount of light is the same or similar to what would be emitted had pixel compensation been performed on each pixel in each subframe. For example, pixel compensation may be performed on every third pixel of the row in a first subframe, and then the pixels on which pixel compensation may be performed may be shifted by a number of pixels in the row. In another example the pixel compensation may be performed on every seventh pixel of a row of eight pixels, such that the first pixel of the row and the eighth pixel are corrected via pixel compensation in a first subframe, the seventh pixel is corrected in a second subframe, the sixth pixel is corrected in a third subframe, and so on. The aforementioned shuffling pattern and/or other shuffling patterns may further reduce an appearance of image artifacts by taking into account an intra-frame pause during a touch sensor operation.

With the preceding in mind, an electronic device10including an electronic display12is shown inFIG.1. As is described in more detail below, the electronic device10may be any suitable electronic device, such as a computer, a mobile phone, a portable media device, a tablet, a television, a virtual-reality headset, a wearable device such as a watch, a vehicle dashboard, or the like. Thus, it should be noted thatFIG.1is merely one example of a particular implementation and is intended to illustrate the types of components that may be present in the electronic device10.

The electronic device10includes the electronic display12, one or more input devices14, one or more input/output (I/O) ports16, a processor core complex18having one or more processing circuitry(s) or processing circuitry cores, local memory20, a main memory storage device22, a network interface24, and a power source26(e.g., power supply). The various components described inFIG.1may include hardware elements (e.g., circuitry), software elements (e.g., a tangible, non-transitory computer-readable medium storing executable instructions), or a combination of both hardware and software elements. It should be noted that the various depicted components may be combined into fewer components or separated into additional components. For example, the local memory20and the main memory storage device22may be included in a single component.

The processor core complex18is operably coupled with local memory20and the main memory storage device22. Thus, the processor core complex18may execute instructions stored in local memory20or the main memory storage device22to perform operations, such as generating or transmitting image data to display on the electronic display12. As such, the processor core complex18may include one or more general purpose microprocessors, one or more application specific integrated circuits (ASICs), one or more field-programmable gate arrays (FPGAs), or any combination thereof.

In addition to program instructions, the local memory20or the main memory storage device22may store data to be processed by the processor core complex18. Thus, the local memory20and/or the main memory storage device22may include one or more tangible, non-transitory, computer-readable media. For example, the local memory20may include random access memory (RAM) and the main memory storage device22may include read-only memory (ROM), rewritable non-volatile memory such as flash memory, hard drives, optical discs, or the like.

The network interface24may communicate data with another electronic device or a network. For example, the network interface24(e.g., a radio frequency system) may enable the electronic device10to communicatively couple to a personal area network (PAN), such as a Bluetooth network, a local area network (LAN), such as an 802.11x Wi-Fi network, or a wide area network (WAN), such as a 4G, Long-Term Evolution (LTE), or 5G cellular network. The power source26may provide electrical power to one or more components in the electronic device10, such as the processor core complex18or the electronic display12. Thus, the power source26may include any suitable source of energy, such as a rechargeable lithium polymer (Li-poly) battery or an alternating current (AC) power converter. The I/O ports16may enable the electronic device10to interface with other electronic devices. For example, when a portable storage device is connected, the I/O port16may enable the processor core complex18to communicate data with the portable storage device.

The input devices14may enable user interaction with the electronic device10, for example, by receiving user inputs via a button, a keyboard, a mouse, a trackpad, or the like. The input device14may include touch-sensing components in the electronic display12. The touch sensing components may receive user inputs by detecting occurrence or position of an object touching the surface of the electronic display12.

In addition to enabling user inputs, the electronic display12may include a display panel with one or more display pixels. The electronic display12may control light emission from the display pixels to present visual representations of information, such as a graphical user interface (GUI) of an operating system, an application interface, a still image, or video content, by displaying frames of image data. To display images, the electronic display12may include display pixels implemented on the display panel. The display pixels may represent sub-pixels that each control a luminance value of one color component (e.g., red, green, or blue for an RGB pixel arrangement or red, green, blue, or white for an RGBW arrangement).

The electronic display12may display an image by controlling light emission from its display pixels based on pixel or image data associated with corresponding image pixels (e.g., points) in the image. In some embodiments, pixel or image data may be generated by an image source, such as the processor core complex18, a graphics processing unit (GPU), or an image sensor. Additionally, in some embodiments, image data may be received from another electronic device10, for example, via the network interface24and/or an I/O port16. Similarly, the electronic display12may display frames based on pixel or image data generated by the processor core complex18, or the electronic display12may display frames based on pixel or image data received via the network interface24, an input device, or an I/O port16.

The electronic device10may be any suitable electronic device. To help illustrate, an example of the electronic device10, a handheld device10A, is shown inFIG.2. The handheld device10A may be a portable phone, a media player, a personal data organizer, a handheld game platform, or the like. For illustrative purposes, the handheld device10A may be a smart phone, such as any IPHONE® model available from Apple Inc.

The handheld device10A includes an enclosure30(e.g., housing). The enclosure30may protect interior components from physical damage or shield them from electromagnetic interference, such as by surrounding the electronic display12. The electronic display12may display a graphical user interface (GUI)32having an array of icons. When an icon34is selected either by an input device14or a touch-sensing component of the electronic display12, an application program may launch.

The input devices14may be accessed through openings in the enclosure30. The input devices14may enable a user to interact with the handheld device10A. For example, the input devices14may enable the user to activate or deactivate the handheld device10A, 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, or toggle between vibrate and ring modes.

Another example of a suitable electronic device10, specifically a tablet device10B, is shown inFIG.3. The tablet device10B may be any IPAD® model available from Apple Inc. A further example of a suitable electronic device10, specifically a computer10C, is shown inFIG.4. For illustrative purposes, the computer10C may be any MACBOOK® or IMAC® model available from Apple Inc. Another example of a suitable electronic device10, specifically a watch10D, is shown inFIG.5. For illustrative purposes, the watch10D may be any APPLE WATCH® model available from Apple Inc. As depicted, the tablet device10B, the computer10C, and the watch10D each also includes an electronic display12, input devices14, I/O ports16, and an enclosure30. The electronic display12may display a GUI32. Here, the GUI32shows a visualization of a clock. When the visualization is selected either by the input device14or a touch-sensing component of the electronic display12, an application program may launch, such as to transition the GUI32to presenting the icons34discussed inFIGS.2and3.

Turning toFIG.6, a computer10E may represent another embodiment of the electronic device10ofFIG.1. The computer10E 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 computer10E may be an iMac®, a MacBook®, or other similar device by Apple Inc. of Cupertino, California. It should be noted that the computer10E may also represent a personal computer (PC) by another manufacturer. A similar enclosure36may be provided to protect and enclose internal components of the computer10E, such as the electronic display12. In certain embodiments, a user of the computer10E may interact with the computer10E using various peripheral input structures14, such as the keyboard14A or mouse14B (e.g., input structures14), which may connect to the computer10E.

FIG.7depicts a block diagram of an example architecture of the electronic display12in the form of a micro-LED display. In the example ofFIG.7, the electronic display12uses an RGB display panel60with pixels that include red, green, and blue micro-LEDs as display pixels. Support circuitry62may receive RGB-format video image data64. It should be appreciated, however, that the electronic display12may, additionally or alternatively, display other formats of image data, in which case the support circuitry62may receive image data of such different image format. In some embodiments, the support circuitry62may include a video timing controller (video TCON) and/or emission timing controller (emission TCON) that receives and uses the image data64in a serial bus to determine a data clock signal (DATA_CLK) and/or a emission clock signal (EM_CLK) to control the provision of the image data64in the electronic display12. The video TCON may also pass the image data64to a serial-to-parallel circuitry that may deserialize the image data64signal into several parallel image data signals. That is, the serial-to-parallel circuitry may collect the image data64into the particular data signals that are passed on to specific columns among a total of M respective columns in the display panel60. As noted above, the video TCON may generate the data clock signal (DATA_CLK), and the emission TCON may generate the emission clock signal (EM_CLK). Collectively, these may be referred to as Data/Row Scan Control signals, as illustrated inFIG.7. The data/row scan controls respectively contain image data corresponding to pixels in the first column, second column, third column, fourth column . . . fourth-to-last column, third-to-last column, second-to-last column, and last column, respectively. The data/row scan controls may be collected into more or fewer columns depending on the number of columns that make up the display panel60.

The display panel60may include microdrivers78. The microdrivers78are arranged in an array79. Each microdriver78drives a number of display pixels77. Different display pixels (e.g., display sub-pixel)77may include different colored micro-LEDs (e.g., a red micro-LED, a green micro-LED, or a blue micro-LED) to represent the image data64in RGB format. Although one of the microdrivers78ofFIG.7is shown to drive twenty-six anodes73having eight display pixels77each, each microdriver78may drive more or fewer anodes73and respective display pixels77. As illustrated, the subset of display pixels77located on each anode73may be associated with a particular color (e.g., red, green, blue). As mentioned above, it should be noted that a respective cathode corresponds to a subset of display pixels77associated with a particular color even though each cathode for a particular color channel is not illustrated inFIG.7. For example, cathode74corresponds to a red color channel (e.g., subset of red display pixels77). Indeed, there may be a second set of cathodes that couple to a green color channel (e.g., subset of green display pixels77) and a third set of cathodes that couple to a blue color channel (subset of blue display pixels77), but these are not expressly illustrated inFIG.7for ease of description.

A power supply84may provide a reference voltage (VREF)86to drive the micro-LEDs, a digital power signal88, and an analog power signal90. In some cases, the power supply84may provide more than one reference voltage (VREF)86signal. Namely, display pixels77of different colors may be driven using different reference voltages. As such, the power supply84may provide more than one reference voltage (VREF)86. Additionally or alternatively, other circuitry on the display panel60may step the reference voltage (VREF)86up or down to obtain different reference voltages to drive different colors of micro-LED.

A block diagram shown inFIG.8illustrates some of the components of one of the microdrivers78. The microdriver78shown inFIG.6includes pixel data buffer(s)100and a digital counter102. The pixel data buffer(s)100may include sufficient storage to hold the image data70that is provided. For instance, the microdriver78may include pixel data buffers to store image data70for a display pixel77at any one time (e.g., for 8-bit image data70, this may be 24 bits of storage). It should be appreciated, however, that the microdriver78may include more or fewer buffers, depending on the data rate of the image data70and the number of display pixels77included in the image data70. The pixel data buffer(s)100may take any suitable logical structure based on the order that the column driver provides the image data70. For example, the pixel data buffer(s)100may include a first-in-first-out (FIFO) logical structure or a last-in-first-out (LIFO) structure.

When the pixel data buffer(s)100has received and stored the image data70, the microdriver78may provide the emission clock signal (EM_CLK). A counter102may receive the emission clock signal (EM_CLK) as an input. The pixel data buffer(s)100may output enough of the stored image data70to output a digital data signal104represent a desired gray level for a particular display pixel77that is to be driven by the microdriver78. The counter102may also output a digital counter signal106indicative of the number of edges (only rising, only falling, or both rising and falling edges) of the emission clock signal (EM_CLK)98. The signals104and106may enter a comparator108that outputs an emission control signal110in an “on” state when the signal106does not exceed the signal104, and an “off” state otherwise. The emission control signal110may be routed to driving circuitry (not shown) for the display pixel77being driven, which may cause light emission112from the selected display pixel77to be on or off. The longer the selected display pixel77is driven “on” by the emission control signal110, the greater the amount of light that will be perceived by the human eye as originating from the display pixel77.

A timing diagram120, shown inFIG.9, provides one brief example of the operation of the microdriver78. The timing diagram120shows the digital data signal104, the digital counter signal106, the emission control signal110, and the emission clock signal (EM_CLK) represented by numeral122. In the example ofFIG.9, the gray level for driving the selected display pixel77is gray level4, and this is reflected in the digital data signal104. The emission control signal110drives the display pixel77“on” for a period of time defined as gray level4based on the emission clock signal (EM_CLK). Namely, as the emission clock signal (EM_CLK) rises and falls, the digital counter signal106gradually increases. The comparator108outputs the emission control signal110to an “on” state as long as the digital counter signal106remains less than the data signal104. When the digital counter signal106reaches the data signal104, the comparator108outputs the emission control signal110to an “off” state, thereby causing the selected display pixel77no longer to emit light.

It should be noted that the steps between gray levels are reflected by the steps between emission clock signal (EM_CLK) edges. That is, based on the way humans perceive light, to notice the difference between lower gray levels, the difference between the amounts of light emitted between two lower gray levels may be relatively small. To notice the difference between higher gray levels, however, the difference between the amounts of light emitted between two higher gray levels may be comparatively much greater. The emission clock signal (EM_CLK) therefore may use relatively short time intervals between clock edges at first. To account for the increase in the difference between light emitted as gray levels increase, the differences between edges (e.g., periods) of the emission clock signal (EM_CLK) may gradually lengthen. The particular pattern of the emission clock signal (EM_CLK), as generated by the emission TCON, may have increasingly longer differences between edges (e.g., periods) so as to provide a gamma encoding of the gray level of the display pixel77being driven.

With the preceding in mind,FIG.10illustrates the microdriver78driving the display pixels77according to the image data70, and thereby enabling image content to be displayed by the electronic display12. As mentioned above, the microdriver78may drive any suitable number of display pixels77, and a subset of display pixels77may be located on respective anodes73of the electronic display12. As illustrated, the subset of display pixels77located on each anode73may be associated with a particular color (e.g., red, green, blue). Further, it should be noted that a respective cathode corresponds to a subset of display pixels77associated with a particular color even though each cathode for a particular color channel is not illustrated inFIG.10. For example, as illustrated, a first set of cathodes corresponds to a red color channel (e.g., subset of red display pixels77). However, there may be a second set of cathodes that couple to a green color channel (e.g., subset of green display pixels77) and a third set of cathodes that couple to a blue color channel (subset of blue display pixels77). The second set of cathodes and the third set of cathodes are not expressly illustrated inFIG.10for ease of description.

FIG.11is an example of driving circuitry1102A,1102B, and1102C (collectively referred to herein as the driving circuitry1102) for driving display pixels77(e.g., of the electronic display12). A current source1104may drive current to each pixel in a row of pixels. For instance, the current sources1104may drive one or more pixels77A,77B, and77C (collectively referred to herein as the pixels77). The pixels77may include red, green, or blue pixels or subpixels.

FIG.12is a schematic diagram of a system1200illustrating a detailed view of driving circuitry (e.g., the driving circuitry1102) for driving subpixels in a row of pixels77. The system1200includes driving circuitry1202A, driving circuitry1202B, and driving circuitry1202C (collectively referred to herein as the driving circuitry1202), which may each be electrically coupled to the microdriver78and the display pixels77and may drive one display pixel77at a time. For example, the drive circuitry1202A may drive blue pixels77, the drive circuitry1202B may drive red pixels77, and the drive circuitry1202C may drive green pixels77. Each drive circuitry may include a series capacitor1204, a parallel capacitor1206, and a control switch1208. The driving circuitries1202may include one or more switching devices1210(e.g., one or more n-channel metal oxide semiconductor (nMOS) field effect transistors or p-channel metal oxide semiconductor (pMOS) field effect transistors) for driving the control switches1208. The switching devices1210may be controlled by an emission pulse signal1212or a bias voltage1214applied to a gate terminal of the switching devices1210.

In some cases, as the control switches1208are opened and closed, capacitive coupling may form at the series capacitors1204and/or the parallel capacitors1206, which may cause distortion in the microdriver78driving the pixels77. This distortion may cause current droop across the pixels77. Moreover, as previously stated, the current droop may increase in each subsequent pixel77in a row of pixels, which may cause each subsequent pixel77in a row of pixels to emit less light than the preceding pixel in the row of pixels. For example, the pixel77A may experience distortion due to the capacitive coupling on the series capacitor1204and/or the parallel capacitor1206, and if the distortion at the77A is not addressed (e.g., an action is not taken at the pixel77to compensate for the current droop at the pixel77), additional distortion may accrue at the subpixel77B. Without compensating for the distortion and current droop, the distortion will continue to accumulate to the pixel77C and the current droop caused by the distortion may be significant enough that the light emitted from the pixel77C may be noticeably less than the light at the pixel77A and the pixel77B, which may result in display image artifacts (e.g., front-of-screen (FOS) artifacts).

The current droop at the pixels77may be reduced or eliminated by performing pixel compensation. Pixel compensation may refresh the charge on the series capacitors1204and/or the parallel capacitors1206, thus removing the distortion from the series capacitors1204and/or the parallel capacitors1206caused by the capacitive coupling of the control switches1208. In some embodiments, pixel compensation may be performed at each row of the pixels77in each subframe of an image frame, thus reducing or eliminating the distortion and reducing or eliminating the current droop across the pixels77. However, performing pixel compensation on all rows in each subframe may consume a prohibitive amount of power. In other embodiments, pixel compensation may be performed on every Nthrow of pixels. For example, if pixel compensation is performed on every 8throw of pixels, the accumulated current droop across the electronic display12may be reduced without consuming excessive power. However, performing pixel compensation in such a pattern may lead to image artifacts (e.g., banding), as will be discussed in greater detail below.

FIG.13is a table1300that may include an amount of current droop across a set of rows of the pixels77that may accumulate at each row across a number of subframes. The table1300illustrates luminance differences for emissions (e.g., emissions from the pixels77in each row within each subframe). The luminance differences may represent a difference between an expected luminance of a particular emission and the actual luminance of the particular emission. For example, using the pixel compensation pattern illustrated in table1300, the luminance difference1302may be equal to 0 when no distortion has accumulated on the pixels77of a row (e.g., no distortion has accumulated on the capacitors1204or1206), or the luminance difference1302may be equal to 0 for a row on which pixel compensation is performed. That is, when pixel compensation is performed on a row during a subframe, the actual emission luminance of the row may be equal to the expected emission luminance of the row during the subframe. The pixel compensation pattern in table1300may be stored in the local memory20or the storage device22of the electronic device10.

As previously discussed, the current droop may accumulate for each row proportional to the length of time that a certain row emits a pulse and the compensated row (e.g., row 0 in the table1300) emits a pulse. For example, in the table1300ofFIG.13, row 1 accumulates some distortion (e.g., due to the capacitive coupling of the driving circuitries1202as described above), but the distortion at row 1 is relatively little, as the microdriver78drives current to row 1 immediately after or a short interval of time after driving current to row 0. However, row 8 accumulates the greatest distortion, as the rows are driven in order and the microdriver78drives current to row 7 after all other rows, and thus the greatest amount of distortion accumulates at row 7 before pixel compensation is performed at row 0 of the subsequent subframe.

As such, the luminance difference increases for each subsequent row in a subframe of the table1300until pixel compensation is again performed on a given row. An average luminance difference1304may be determined based on the luminance difference for a given row across all subframes (e.g., 16 subframes, as shown in the table1300).

Moreover, the total luminance difference across all rows for the entire frame may be calculated by multiplying an estimated current droop across the image frame by the difference between the maximum average luminance for the frame and the minimum average luminance for the frame divided by the number of rows emitting in the frame. That is, the total luminance difference for a particular row across the frame in the table1300can be represented by the equation

In the equation, idroopis the estimated output current droop across each subframe, LMAXis the maximum average luminance difference for the image frame, LMINis the minimum average luminance difference for the image frame, and N is the number of rows in the image frame. For example, the estimated current droop across the image frame (independent of whether the frame is displaying at 480 Hertz (Hz), 960 Hz, or another appropriate frequency) may be equal to approximately 3.3% (e.g., for a nominal current of 0.3 microamps). As such, the total luminance difference for the pixel compensation pattern illustrated in table1300ofFIG.13may be determined using the equation described above accordingly:

As stated above, while performing the pixel compensation may reduce or eliminate the current droop at a row, certain pixel compensation patterns may lead to an image artifact, as is illustrated inFIG.14as may be seen from the image artifact1400that may be displayed on the electronic display12. Because pixel compensation is performed at every 1strow (i.e., row 0) across the subframes displayed on the electronic display12(e.g., as is shown in the table1300ofFIG.13), certain image artifacts may be visible across the electronic display12.

FIG.14is an illustration of an image artifact1400that may be caused by the pixel compensation pattern shown in the table1300. As may be observed, since the pixel compensation is performed at the same row (i.e., row 0) across each subframe inFIG.13, there is significantly less current droop across the upper rows (e.g., meaning the pixels in the upper rows exhibit less luminance difference and may emit brighter light) and significantly more current droop across the lower rows (e.g., meaning the pixels in the lower rows exhibit greater luminance difference and may emit dimmer light). As this pattern is repeated for the rows of the pixels77in the electronic display12, the image artifact1400displayed on the electronic display12may exhibit a banding pattern that may negatively impact user experience. To address this, various pixel compensation patterns may be used to produce similar average luminance differences1304for all rows across the subframes of a frame.

FIG.15is a table1500that tracks another pixel compensation pattern and stores average luminance differences for each row of pixels77in each subframe of a frame. As illustrated, the table1500may include emissions at each row across 8 rows of pixels77for a frame that includes 16 subframes. While 8 rows are shown, it should be noted that the table1500may store data for any appropriate number of rows (e.g., 9 rows or more, 10 rows or more, 20 rows or more, 100 rows or more). Additionally, a frame may be divided up into any appropriate number of subframes (e.g., 2 subframes or more, 4 subframes or more, 10 subframes or more, 20 subframes or more, 50 subframes or more). Similarly to the table1300inFIG.13, the luminance differences1302in the table1500may be 0 at a particular row on which pixel compensation is performed, and the luminance difference1302may increase with each subsequent row until the pixel compensation is again performed.

As may be observed, the pixel compensation pattern for the table1500may include performing pixel compensation whenever the row number is equal to the subframe number for subframes 1-8. For example, at subframe 6, the pixel compensation is performed at row 6. For subframes 9-16, the pixel compensation may be performed when the row counter is equal to the difference between 17 and the subframe number. For example, for subframe 10, the pixel compensation may be performed at row 7. The average luminance difference1304for each row across all 16 subframes (i.e., across one frame) may also be stored in the table1500. As may be observed, due to the pixel compensation pattern illustrated in the table1500, the average luminance difference1304for the rows in the table1500are much closer than the average luminance differences1304in the table1300inFIG.13.

Due to the similarity in the average luminance difference for each row, the rows may output similar brightness levels, and the banding issue illustrated inFIG.14may be decreased or eliminated. Given the values in the table1500, the total luminance difference across all 8 rows for the entire frame may be determined using the equation described above as follows:

As such, the pixel compensation pattern inFIG.15nearly averages out the current droop and subsequent luminance difference across the image frame.

FIG.16is a table1600using the same pixel compensation pattern illustrated in the table1500inFIG.15, however the table1600takes into account additional current droop due to intra-frame pause (IFP)1602. Intra-frame pause1602may cause additional distortion in the microdriver78during touchscreen operation of the electronic display12(e.g., when a user of the electronic device10interacts with the touchscreen-enabled electronic display12). As may be observed in the table1600, IFP1602may cause an additional luminance difference (e.g., an additional luminance difference of 0.7%), resulting in an additional luminance difference every two subframes.

As may be observed from the average luminance difference1304, IFP1602may increase the average luminance difference1304for each row across the frame, and thus may increase the total average luminance difference across the entire image frame. Using the formula for total luminance difference across all rows for the image frame as discussed above, the total luminance difference for the image frame illustrated by the table1600may be calculated accordingly:

As such, it may be appreciated that, while the IFP1602may cause additional luminance difference across the image frame, the applied pixel compensation pattern may still effectuate a greater reduction in luminance difference than other pixel compensation patterns (e.g., the pixel compensation pattern discussed inFIG.13). It should be noted that, while the IFP1602is shown inFIG.16to occur between every two subframes, IFP may occur between at any appropriate interval (e.g., every subframe, every three subframes, every four subframes, every eight subframes, every ten subframes, and so on).

In certain embodiments, a shuffling pattern may be applied to the emission timing for the pixels77of the electronic display12. The pixel compensation patterns discussed previously may not average out the luminance difference across the electronic display12when applied to an electronic display12having a shuffled emission pattern (e.g., such that the pixel compensation may not prevent an image artifact from occurring on the electronic display12). As such, using a shuffled emission pattern may cause greater luminance difference across the image frame even when pixel compensation patterns (e.g., the pixel compensation patterns illustrated inFIGS.15and16) are applied. As such, in certain embodiments, another pixel compensation pattern may be applied that accounts for the shuffled emission pattern.

FIG.17includes an example of shuffled emission pattern1700that may be applied across a frame, and a table1710illustrating an application of a shuffled emission pattern and a shuffled pixel compensation pattern. The values shown in the shuffled emission pattern represent the order in which the rows (e.g., the pixels77in the rows) emit pulses of light. As may be observed, when a shuffled emission pattern is applied to the pixels77in the rows, the rows of the pixels77may not emit in a sequential manner (i.e., row 1 may not emit first, row 2 may not emit following row 1, row 3 may not emit following row 2, and so on). The circled values represent two pixels compensation patterns1702and1704that may account for the shuffled emission pattern. The pixel compensation pattern1702may be performed on the first four subframes of a frame (e.g., as may be observed from subframes 1 through 4 of the table1710) while the pixel compensation pattern1704may be performed on the next four subframes of a frame (e.g., as may be observed from subframes 5 through 8 of the table1710). As may be observed from the table1710, the pixel compensation patterns1702and1704may repeat in reverse order for the remaining eight subframes of the frame. In some embodiments, the emission shuffling patterns (e.g.,1700) may be random, while in other embodiments the pattern may be deterministic.

The shuffled emission pattern1700may increase the luminance difference across the rows of the electronic display12. By applying the equation described above, luminance difference for the shuffled emission pattern1700, even accounting for the pixel compensation patterns1702and1704may be represented accordingly:

As such, it may be desirable to apply one or more pixel compensation patterns that may account for shuffled emission pattern schemes.

FIG.18illustrates multiple pixel compensation patterns that may be effective in reducing or eliminating luminance differences caused by current droop in an electronic display (e.g.,12) utilizing a sequential emission pattern.FIG.18includes a table1802including sequential emission pattern1808and a pixel compensation pattern whereby pixel compensation is performed on every 7throw across 16 subframes, a table1804including the sequential emission pattern1808and a pixel compensation pattern whereby pixel compensation is performed on every 5throw across 16 subframes, and a table1806including the sequential emission pattern1808and a pixel compensation pattern whereby pixel compensation is performed on every 3rdrow across 16 subframes.

By performing pixel compensation on every 7throw, every 5throw, or every 3rdrow, the total luminance difference across the frame may be reduced or eliminated. Applying the total luminance difference equation to the table1802, the total luminance difference across the frame may be determined as follows:

Applying the equation to the table1804, the total luminance difference across the frame may be determined as follows:

Applying the equation to the table1806, the total luminance difference across the frame may be determined as follows:

As such, by performing pixel compensation on every 7throw, 5throw, or 3rdrow, the total luminance difference across an image frame may be kept at or below approximately 0.3% while consuming less power than would be consumed if pixel compensation were to be performed on each row across each subframe.

FIG.19illustrates how the pixel compensation patterns described inFIG.18may be effective in reducing or eliminating luminance differences caused by current droop in an electronic display (e.g.,12) utilizing a shuffled emission pattern.FIG.19includes a table1902including shuffled emission pattern1908and a pixel compensation pattern whereby pixel compensation is performed on every 7throw across 16 subframes, a table1904including the shuffled emission pattern1908and a pixel compensation pattern whereby pixel compensation is performed on every 5throw across 16 subframes, and a table1906including the shuffled emission pattern1908and a pixel compensation pattern whereby pixel compensation is performed on every 3rdrow across 16 subframes.

By performing pixel compensation on every 71row, every 5throw, or every 3rdrow, the total luminance difference across the frame may be reduced or eliminated. Applying the equation described above to the table1902, the total luminance difference across the frame may be determined as follows:

Applying the equation to the table1804, the total luminance difference across the frame may be determined as follows:

Applying the equation to the table1806, the total luminance difference across the frame may be determined as follows:

As such, by performing pixel compensation on every 7throw, 5throw, or 3rdrow, the total luminance difference across an image frame may be kept at or below approximately 0.75% while consuming less power than would be consumed if pixel compensation were to be performed on each row across each subframe.

FIG.20illustrates how the pixel compensation patterns described inFIG.18may be effective in reducing or eliminating luminance differences caused by current droop in an electronic display (e.g.,12) utilizing another shuffled emission pattern.FIG.20includes a table2002including shuffled emission pattern2008and a pixel compensation pattern whereby pixel compensation is performed on every 7throw across 16 subframes, a table2004including the shuffled emission pattern2008and a pixel compensation pattern whereby pixel compensation is performed on every 5throw across 16 subframes, and a table2006including the shuffled emission pattern2008and a pixel compensation pattern whereby pixel compensation is performed on every 3rdrow across 16 subframes.

By performing pixel compensation on every 7throw, every 5throw, or every 3rdrow, the total luminance difference across the frame may be reduced or eliminated. Applying the equation to the table1902, the total luminance difference across the frame may be determined as follows:

Applying the equation to the table1804, the total luminance difference across the frame may be determined as follows:

Applying the equation to the table1806, the total luminance difference across the frame may be determined as follows:

As such, by performing pixel compensation on every 7throw, 5throw, or 3rdrow, the total luminance difference across an image frame may be kept at or below approximately 0.50% while consuming less power than would be consumed if pixel compensation were to be performed on each row across each subframe.

As may be appreciated, by applying pixel compensation to each 7throw, 5throw, or 3rdrow, total luminance difference across the frame (and thus FOS artifacts on the electronic display12) may be reduced without consuming excessive power and may reduce luminance difference across the frame when accounting for additional luminance difference due to IFP1602and/or various emission patterns. While performing pixel compensation on every 7th, 5thand 3rdrow in the frame is shown and discussed inFIGS.18,19, and20above, it should be noted that many pixel compensation methods may be used. However, to increase the effectiveness of the pixel compensation, the interval and the number of rows may be mutually prime. For example, for 8 rows of pixels (as discussed above), performing pixel compensation on every row, every 3rdrow, every 5throw, and every 7throw may provide effective reduction of luminance differences and thus potentially an effective reduction in image artifacts. However, performing pixel compensation on every 2ndrow, every 4throw, every 6th, row, or every 8throw may be less effective in reducing the luminance differences, as the common divisors may result in the same rows receiving pixel compensation repeatedly, and thus may result in some rows emitting consistently brighter light (due to the reduced current droop on those rows) and other rows emitting consistently dimmer light (due to the unmitigated current droop on those rows) across the image frame.