Display system with pixel burn-in compensation

Abstract

In general, the subject matter described in this disclosure can be embodied in methods, systems, and program products for presenting display content on a display of a computing system. A method includes identifying multiple zones of a display device for which to monitor usage, with each zone of the multiple zones being formed of a corresponding group of multiple pixels. The multiple zones are formed of different quantities of pixels that increase with distance from a center of the display device. The method includes determining multiple usage values for the multiple zones of the display device, by determining, for each zone, a usage value based on content presented by pixels of the zone; determining a most-used zone of the multiple zones; and modifying an output sent to pixels of the display device to reduce effects of pixel burn-in.

Description

Attomey Docket No.: 56113-0816WO1DISPLAY SYSTEM WITH PIXEL BURN-IN COMPENSATIONTECHNICAL FIELD

[0001] This document generally relates to display devices such as organic light emitting diode (OLED) devices.BACKGROUND

[0002] Electronic devices can include display systems on which visual images are shown. Display panel pixels can experience a degradation in visible intensity over time. For example, a luminance of a pixel, which is produced by an electrical current that is designated by a given encoded pixel level, may decrease over time due to usage. This reduction of pixel luminosity with use can result in pixel bum-in, in which more-used pixels appear different than less-used pixels.SUMMARY

[0003] This document describes techniques, methods, systems, and other mechanisms for providing a display system with pixel bum-in compensation. In display systems, such as organic light-emitting diode (OLED) display devices, OLED material efficiency can degrade over time. Display degradation can be accelerated due to high current densities (e.g., high luminance), high refresh rates, and conditions such as high temperatures. Display degradation can result in decreasing pixel brightness with usage. For example, at a given driving voltage supplied to a driving transistor of a pixel or sub-pixel, an OLED of the pixel or sub-pixel may become dimmer over time. Pixel degradation over time can be referred to as bum-in.

[0004] The techniques described herein can be implemented to improve display quality by compensating for pixel bum-in. Pixel usage is monitored in multiple different zones of a display panel that are each formed of multiple pixels. The pixel usage is used to determine the efficiency of the zones. Image data is then modified for portions of images corresponding to the monitored zones. As a result, lesser-used zones of the display, when presenting the modified image data, show a same or similar pixel intensity as more-used zones of the display. This improves the quality of the displayed image and extends panel lifetime.

[0005] The described compensation techniques can maintain consistent brightness and color across the display and can extend OLED lifetime. The disclosed techniques can be used to reduce power consumption while monitoring pixel usage and compensating for pixel bum-Attorney Docket No.: 56113-0816WO1 in. For example, monitoring usage of zones of pixels instead of monitoring individual pixels improves power efficiency. Similarly, sampling frames at reduced sampling rates reduces power consumption and use of computational resources.

[0006] The disclosed techniques improve consistency of pixel intensity throughout the display while maintaining or enhancing user experience. Users typically focus on content near the center of the display. Therefore, monitored display zones nearer to the center of the display may be smaller than monitored display zones farther from the center of the display. Bum-in compensation can therefore be more fine-tuned near the center of the display compared to the peripheral areas of the display. In some cases, borders between zones may avoid the center of the display in order to make the borders less perceptible to a user.

[0007] As additional description to the embodiments described below, the present disclosure describes the following embodiments.

[0008] Embodiment 1 is directed to a method to reduce effects of display bum-in, comprising: identifying, by a computing device, multiple zones of a display device for which to monitor usage, with each zone of the multiple zones being formed of a corresponding group of multiple pixels, wherein the multiple zones are formed of different quantities of pixels that increase with distance from a center of the display device, such that a first zone of the multiple zones is formed of fewer pixels than a second zone of the multiple zones that is further from the center of the display device than the first zone; determining, by a computing device, multiple usage values for the multiple zones of the display device, by determining, for each zone of the multiple zones, a usage value based on content presented by pixels of the zone; determining, by the computing device, a most-used zone of the multiple zones based on the usage value for the most-used zone representing a greatest amount of usage among the multiple zones; and modifying, by the computing device based on having determined the most-used zone and the multiple usage values for the multiple zones, an output sent to pixels of the display device to reduce effects of pixel bum-in.

[0009] Embodiment 2 is the method of embodiment 1, wherein determining the multiple usage values for the multiple zones of the display device includes, for each zone of the multiple zones: updating a histogram that is specific to the zone by adding to the histogram an intensity' value that represents an intensity of content presented by pixels of the zone, repeatedly for different presentations of content by pixels of the zone at different times; and determining the usage value for the zone based on intensity values of the histogram that is specific to the zone.Attorney Docket No.: 56113-0816WO1

[0010] Embodiment 3 is the method of any one of the embodiments 1 or 2, comprising: determining the intensity value that represents the intensity of content presented by pixels of the zone, by combining multiple pixel values for pixels of the zone into a single value.

[0011] Embodiment 4 is the method of any one of the embodiments 1 through 3, wherein combining the multiple pixel values for pixels of the zone into the single value includes averaging the multiple pixel values.

[0012] Embodiment 5 is the method of any one of the embodiments 1 through 4. wherein the pixels of the zone for which the multiple pixel values are combined are adapted to present a same color channel.

[0013] Embodiment 6 is the method of any one of the embodiments 1 through 5, wherein: the multiple zones include a third zone that is further from the center of the display device than both the second zone and the first zone; and the third zone is formed of more pixels than both the second zone and the first zone.

[0014] Embodiment 7 is the method of any one of the embodiments 1 through 6, wherein: the first zone has a first height in pixels; the second zone has a second height in pixels, the second height being greater than the first height; and the third zone has a third height in pixels, the third height being greater than both the second height and the first height.

[0015] Embodiment 8 is the method of any one of the embodiments 1 through 7, wherein: the first zone has a first width in pixels; the second zone has a second width in pixels, the second width being greater than the first width; and the third zone has a third width in pixels, the third width being greater than both the second width and the first width.

[0016] Embodiment 9 is the method of any one of the embodiments 1 through 8, wherein: the second zone completely surrounds the first zone.

[0017] Embodiment 10 is the method any one of the embodiments 1 through 9, wherein: the first zone has a rectangle shape; and the second zone has an "‘L” or “U” shape.

[0018] Embodiment 11 is the method of any one of the embodiments 1 through 10, wherein determining the multiple usage values for the multiple zones of the display device includes, for each zone of the multiple zones: combining intensity values that represent an intensity of content presented by pixels of the zone at different times with data that indicates different temperatures of the display device at the different times, to generate the usage value for the zone, such that the usage value for the zone accounts for increased usage that results from outputting content at increased temperatures.

[0019] Embodiment 12 is the method of any one of the embodiments 1 through 11, wherein determining the multiple usage values for the multiple zones of the display deviceAttorney Docket No.: 56113-0816WO1 includes, for each zone of the multiple zones: combining intensity values that represent an intensity of content presented by pixels of the zone at different times with data that indicates different refresh rates of the display device at the different times, to generate the usage value for the zone, such that the usage value for the zone accounts for both intensities of presented content and refresh rates.

[0020] Embodiment 13 is the method of any one of the embodiments 1 through 12, wherein determining the multiple usage values for the multiple zones of the display device includes, for each zone of the multiple zones: combining intensity values that represent an intensity of content presented by pixels of the zone at different times with data that indicates different overall display brightness values for the display device at the different times, to generate the usage value for the zone, such that the usage value for the zone accounts for both intensities of presented content and overall display brightness values.

[0021] Embodiment 14 is the method of any one of the embodiments 1 through 13, wherein modifying the output sent to the pixels of the display device to reduce effects of pixel bum-in includes: modifying the output sent to pixels of other zones of the multiple zones other than the most-used zone, to dim content presented by the other zones and limit a maximum luminance of the other zones to a maximum luminance of the most-used zone.

[0022] Embodiment 15 is the method of any one of the embodiments 1 through 14, wherein: inner zones are zones of the multiple zones that are closer to the center of the display device than the most-used zone; the other zones represent zones of the multiple zones other than the most-used zone and the inner zones; and modifying the output sent to the pixels of the display device to reduce effects of pixel bum-in includes modifying the output sent to pixels of the inner zones to dim content presented by the inner zones and limit a maximum luminance of the inner zones to intensities that are greater than the maximum luminance of the most-used zone.

[0023] Embodiment 16 is the method of any one of the embodiments 1 through 15, wherein modifying the output sent to the pixels of the display device to reduce effects of pixel bum-in, includes: modilying the output sent to pixels of other zones of the multiple zones other than the most-used zone, to dim content presented by the other zones a proportional amount based on differences between the usage values for the other zones and the usage value for the most-used zone.

[0024] Embodiment 17 is the method of any one of the embodiments 1 through 16, wherein the multiple zones of the display device comprise a subset of all zones of the display device.Attorney Docket No.: 56113-0816WO1

[0025] Embodiment 18 is the method of any one of the embodiments 1 through 17, wherein the multiple zones of the display device comprise two neighboring zones of the display device.

[0026] Embodiment 19 is the method of any one of the embodiments 1 through 18, wherein the multiple zones comprise a first set of multiple zones, the method comprising: identifying, by the computing device, a second set of multiple zones of the display device for which to monitor usage, with each zone of the second set of multiple zones being formed of a corresponding group of multiple pixels; determining, by the computing device, a second set of multiple usage values for the second set of multiple zones of the display device, by determining, for each zone of the second set of multiple zones, a usage value based on content presented by pixels of the zone; determining, by the computing device, a most-used zone of the second set of multiple zones; and modifying, by the computing device based on having determined the most-used zone and the second set of multiple usage values for the second set of multiple zones, a second output sent to pixels of the display device to reduce effects of pixel bum-in.

[0027] Embodiment 20 is a computing device, comprising: one or more processors; and one or more storage devices including instructions, that when executed by the one or more processors, cause the computing device to perform operations that include: identifying, by the computing device, multiple zones of a display device for which to monitor usage, with each zone of the multiple zones being formed of a corresponding group of multiple pixels, wherein the multiple zones are formed of different quantities of pixels that increase with distance from a center of the display device, such that a first zone of the multiple zones is formed of fewer pixels than a second zone of the multiple zones that is further from the center of the display device than the first zone; determining, by a computing device, multiple usage values for the multiple zones of the display device, by determining, for each zone of the multiple zones, a usage value based on content presented by pixels of the zone; determining, by the computing device, a most-used zone of the multiple zones based on the usage value for the most-used zone representing a greatest amount of usage among the multiple zones; and modifying, by the computing device based on having determined the most-used zone and the multiple usage values for the multiple zones, an output sent to pixels of the display device to reduce effects of pixel bum-in.

[0028] Embodiment 21 is the computing device of embodiment 20, wherein determining the multiple usage values for the multiple zones of the display device includes, for each zone of the multiple zones: updating a histogram that is specific to the zone by adding to theAttorney Docket No.: 56113-0816WO1 histogram an intensity value that represents an intensity of content presented by pixels of the zone, repeatedly for different presentations of content by pixels of the zone at different times; and determining the usage value for the zone based on intensity values of the histogram that is specific to the zone.

[0029] Embodiment 22 is the computing device of any one of the embodiments 20 or 21, the operations comprising: determining the intensity value that represents the intensity of content presented by pixels of the zone, by combining multiple pixel values for pixels of the zone into a single value.

[0030] Embodiment 23 is the computing device of any one of the embodiments 20 through 22, wherein combining the multiple pixel values for pixels of the zone into the single value includes averaging the multiple pixel values.

[0031] Implementations of the above techniques include methods, apparatus, systems, and computer program products. One such computer program product is suitably embodied in a non-transitory machine-readable medium that stores instructions executable by one or more processors. The instructions are configured to cause the one or more processors to perform the above-described actions.

[0032] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.DESCRIPTION OF DRAWINGS

[0033] FIG. 1 shows a diagram of an example display system of an electronic device.

[0034] FIG. 2 shows a block diagram of a system for compensating pixel bum-in.

[0035] FIGS. 3A to 3E show example zones of a display device for monitoring pixel usage and for modifying content to reduce the effects of pixel bum-in.

[0036] FIG. 4 shows a timing diagram of monitoring zone usage of a display device.

[0037] FIG. 5 A shows example calculations of total zone usage for multiple zones of a display device.

[0038] FIG. 5B shows an example graph including a curve representing zone efficiency vs. total zone usage for a display device.

[0039] FIG. 6 shows a flowchart of a process for operating a display device with pixel bum-in compensation.

[0040] FIG. 7 shows a block diagram of computing devices that may be used to implement the systems and methods described in this document.Attorney Docket No.: 56113-0816WO1

[0041] Like reference symbols in the various drawings indicate like elements.DETAILED DESCRIPTION

[0042] This document generally describes mechanisms for providing a display device with pixel bum-in compensation.

[0043] The following discussion of the figures provides additional detail regarding such mechanisms to mitigate effects of pixel bum-in. The discussion of FIG. 1 provides an overview of operation of a display device and components therein, with FIGS. 2 to 6 describing how such components can be operated to compensate for pixel bum-in.

[0044] FIG. 1 is a diagram of an example display sy stem 100 of computing device 190. The device 190 includes a display panel 104 housed in a chassis 109. A region of the device 190 between the edge of the panel 104 and the edge of the chassis is a bezel region 103.

[0045] The display panel 104 is an OLED display panel 104 that includes an array 112 of light emitting pixels. Each light emitting pixel includes an OLED. The OLED display is driven by drivers, including SCAN / EM drivers 108 and data drivers 110. The SCAN / EM drivers 108 can be integrated, i.e.. stacked, row line drivers. In general, the data drivers 110 provide data signals (e.g., voltage data (VDATA)) to the data lines (e.g., D1-D3), the SCAN / EM Drivers 108 provides a SCAN signal to a selected one of the scan lines (e.g., SCAN1) move the data signals from the data lines to the pixels in the selected scan line, and the SCAN / EM Drivers 108 provide an EMISSION signal to a selected one of the emission lines (e.g., El) to light the OLEDs in the selected row according to image data specified by the data signals. Although FIG. 1 illustrates the display system 100 having the SCAN / EM drivers 108 on a single side of the display, the SCAN / EM drivers 108 can be placed on both left and right sides of the display to improve driving performance (e.g.. increasing speed by having SCAN drivers on the left side of the display and the EM drivers on the right side of the display).

[0046] The pixel array 112 includes a plurality' of light emitting pixels, for example, the pixels Pl 1 through P34. A pixel is a small element of a display that can change color based on the image data supplied to the pixel. Each pixel includes an OLED and circuitry to address the OLED with a data value, store the data value, and drive the OLED at an intensity based on the data value. Each pixel within the pixel array 112 can be addressed individually to produce various intensities of a color produced by the pixel. Each pixel maintains a mostly steady luminance throughout a frame time, displaying light corresponding to the supplied image data.Attorney Docket No.: 56113-0816WO1

[0047] The light intensity of a pixel may be determined by a grayscale value. Pixel light intensities can be represented as grayscale values that include integers from zero to 255, representing an example 8-bit grayscale display. Other grayscale value ranges can be used. For example, grayscale values may range from zero to 1023 for a 10-bit display, or from zero to 65535 for a 16-bit display. Other possible grayscale value ranges may include a range from zero to one, with fractional values in between, and a range from zero percent (%) to 100%.

[0048] For a full color display that spatially synthesizes color, each pixel may include multiple color channels, or subpixels. In some examples, each pixel may include each of a red, green, and blue subpixel. In some examples, each pixel may include each of a cyan, magenta, and yellow subpixel. The light intensities of each subpixel may be represented with grayscale values as described above, e.g., integers from zero to 255 for an 8-bit display.

[0049] Luminance is the amount of light emitted by the surface area of a light source such as a pixel or a display. Display luminance is the luminous intensity coming from the surface of the display. Luminance can be measured in units such as candelas per square meter (cd / m2), which are also referred to as "nils."

[0050] A frame time, or frame period, is an amount of time between a start of a frame and a start of a next frame. The frame time can be the inverse of a frame rate of a display system. For example, a frame rate of 60 frames per second (fps) corresponds to a frame time of one- sixtieth of a second, or 0.0167 seconds.

[0051] The pixel array 112 extends in a plane and includes rows and columns. Each row extends horizontally across the pixel array 1 12. For example, the first row 120 of the pixel array 112 includes pixels Pl 1, P21, and P31. Each column extends vertically down the pixel array 112. For example, the first column 130 of the pixel array 112 includes pixels Pl 1, P12. P13, and P14. Only a few pixels are shown in FIG. 1 for simplicity. In practice, there may be thousands or millions of pixels in the pixel array 112. Increasing the numbers of pixels in a display that remains the same size results in a higher image resolution.

[0052] The display system 100 includes a display driver integration circuit (DDIC) 106 that receives display input data 102. The display input data 102 can include color values for each pixel of the pixel array 112. The color value for a pixel corresponds with a color to be emitted by the pixel. In some examples, the display input data 102 can include brightness values for each pixel of the pixel array 112. The brightness value for a pixel corresponds with a brightness of the light to be emitted by the pixel.

[0053] In some examples, the display input data 102 includes a pixel value that incorporates both color data and brightness data. The RGB values of typical digital images doAttorney Docket No.: 56113-0816WO1 not directly correspond to the physical light intensities, but are rather compressed by a gamma correction function. This transformation better utilizes the limited number of bits in the encoded image by choosing a gamma value that matches the non-linear human perception of luminance. For example, the display input data 102 can include a gamma corrected pixel value for each subpixel of each pixel of the array 112. Addressing a pixel using the gamma corrected pixel value causes the pixel to emit light at the color and brightness specified by the gamma corrected pixel value.

[0054] In some examples, the DDIC 106 receives the display input data 102 from a system-on-chip (SoC) 105. The SoC 105 is a microchip with all the necessary electronic circuits and parts for a given system, such as a smartphone or wearable computer, on a single integrated circuit (IC). The SoC 105 is an integrated circuit that includes multiple components on a single chip. The SoC 105 can include, for example, a processor, a memory, and input / output (I / O) ports. The SoC 105 can be implemented on a single substrate, such as silicon. The SoC 105 can process digital signals, analog signals, and mixed signals.

[0055] The DDIC 106 can be, for example, a semiconductor integrated circuit or a state machine. The DDIC 106 generates signals with suitable voltage, current, timing, and demultiplexing to cause a display panel 104 to show images according to display input data 102. In some examples, the DDIC 106 can be a microcontroller and may incorporate RAM, Flash memory, EEPROM, ROM, etc.

[0056] The DDIC 106 drives the pixel array 112 to emit light according to the display input data 102. For example, the data signal generator 138 of the DDIC 106 generates image data signals 144 from the display input data 102 and provides the image data signals 144 to the data drivers 110. The image data signals 144 can include voltages for each subpixel of the pixel array 112 to drive the subpixels to emit light at a color and brightness specified by the display input data 102.

[0057] The DDIC 106 includes a timing controller 134, a clock signal generator 136, and a data signal generator 138. The DDIC 106 generates control signals 142. The control signals 142 can include, for example, signals that control a display frame start time and a display frame stop time of each frame presented by the display panel 104, where a frame represents a single image in a sequence of images that are presented by the display panel 104. In examples in which each frame presented by the display panel includes multiple emission cycles, the control signals 142 or other signals not illustrated in FIG. 1 can control a display emission start time and a display emission stop time of each emission cycle of the display panel 104.Attorney Docket No.: 56113-0816WO1

[0058] In some examples, the SCAN / EM drivers 108, the data drivers 110, or both, can be integrated with the DDIC 106. The SCAN / EM drivers supply SCAN and EM signals to rows of the pixel array 112. For example, the SCAN / EM drivers 108 supply scan signals via scan lines SI to S4, and EM signals via EM lines El to E4, to the rows of pixels, with each row of pixels in the pixel array 112 being addressed by a scan line and a corresponding emission line. For example, the first row 120 of the pixel array 112 is addressed by scan line SCAN! and emission line El.

[0059] The data drivers 110 supply signals to columns of the pixel array 112. For example, based on the image data signal 144 from the data signal generator 138, the data drivers 110 output data values via source amp output signal lines SAN (e g., a set of source amp signal lines SAI, SA2, and SA3) to a set of multiplexers 114 in the panel 104. The set of multiplexers 114 in the panel 104 receive data values from a corresponding set of source amp output signal lines SAN, and route the received data values among a greater number of data lines. For example. FIG. 1 illustrates a single MUX 114 that is configured to receive a stream of data values from the data driver 110 via the source output signal line SAI. and distribute the stream of data values one at a time among the data signal lines DI -3. In practice there would likely be multiple MUXs, each being fed with data values from the data drivers 110 via a corresponding source control signal line.

[0060] The data drivers 110 supply data voltages via the data lines DI to D3. In some examples, each of the data lines DI to D3 represent multiple data lines. For example, the pixel P l 1 can include three subpixels (e.g., Pl 1R for a red subpixel, Pl 1 G for a green subpixel, and Pl IB for a blue subpixel), and the data line DI can represent three corresponding data lines, each addressing a corresponding subpixel of pixel PIE

[0061] The control signals 142 can be used to drive the SCAN / EM drivers 108 and the data drivers 110. Thus, the DDIC 106 controls the timing of the scan signals, EM signals, and data signals.

[0062] The display system 100 includes a power supply 150. The power supply 150 provides a first supply voltage ELVDD and a second supply voltage ELVSS. both of which are provided to each pixel in the pixel array 112. In some examples, the power supply 150 can be integrated with the DDIC 106.

[0063] Each pixel in the pixel array 112 is addressable by a horizontal scan line, a horizontal EM line, and a vertical data line. For example, the pixel Pl 1 is addressable by the data line DI, the scan line SI, and the EM line El. In another example, the pixel P23 is addressable by the data line D2, the scan line S3, and the EM line E3.Attorney Docket No.: 56113-0816WO1

[0064] The scan lines are addressed sequentially for each frame. A scan direction determines an order in which the scan lines are addressed (e.g., a direction in which rows of pixels receive data values and then light up at intensities based on the received data values). In the display system 100, the scan direction is from a top of the pixel array 112 to a bottom of the pixel array 112. For example, the scan line SI is addressed first, followed by the scan line S2, then S3, etc. In some implementations, all rows of pixels are programmed with data values using SCAN signals (one row at a time), before the display device activates all rows of pixels at intensities based on the programmed data values. In some implementations, a display device may activate rows of pixels while other rows of pixels are still being programmed, such that there is a gap of a few rows between a row currently receiving a SCAN signal and a row of pixels that is activated and begins emitting light.

[0065] While FIG. 1 illustrates that each row is addressed by a single scan line, each row may be addressed by multiple scan lines (e.g., nSCAN and pSCAN). Although FIG. 1 illustrates example components of an OLED display, the described techniques may be applied to other flat panel display technologies that include an array of pixels. The techniques can be applied to curved displays, flexible displays, foldable displays, and rollable displays. For example, the technology may be applied to light emitting diode displays (LED), liquid cry stal displays (LCD), and plasma display panels (PDP). The technology7can also be applied to projectors (e.g., digital light processing projectors) to reduce power consumption and to reduce the amount of heat absorbed and dissipated by the projector.

[0066] FIG. 2 shows a block diagram of a system 200 for compensating pixel bum-in. The system 200 compensates an image to be shown on a display (e.g., the display panel 104).

[0067] The system 200 includes the SoC 105 and the DDIC 106 of the display sy stem 100. The SoC 105 includes a processor 204. The processor 204 includes a zone usage calculator 210, a bum-in compensator 220, and an alpha layer 224.

[0068] The processor 204 can be, for example, a Graphical Processing Unit (GPU). The processor 204 can include, for example, a bus interface, a power management unit, a video processing unit, a graphics memory controller, a display interface, or any combination of these. The processor 204 can include a digital signal processor (DSP). The DSP can perform signal processing operations such as data collection and data processing.

[0069] When generating and displaying images on the display panel 104 of the device 190, the processor 204 can generate visual content data, such as a frame of a video. The visual content data may be for a video sequence that is pre-rendered, e.g., for a film. The visual content data may be for a video sequence that is dynamically generated, e.g., for aAttorney Docket No.: 56113-0816WO1 video game or for user navigation through various operating system screens and menus. In some examples, the visual content data can be compressed, using any appropriate method. In some examples, the visual content data can be uncompressed. The processor 204 can store the generated visual content data in a meniop . The memory may be any appropriate type of memory. For instance, the memory' can be a random access memory' (RAM).

[0070] The SoC 105 can receive, as input, image data 201, a display brightness setting (e.g.. display brightness value (DBV) 212), a temperature 214, a refresh rate 216, or any combination of these. The image data 201 can be, for example, image data for an image frame in a sequence of frames to be presented by the display panel 104.

[0071] The DBV 212 can be a setting of display brightness. The DBV 212 can be an arbitrary number used for computation of display brightness, or a setting that specifies an amount of nits. The DBV 212 can represent an overall brightness of the display system. The DBV can be set by a user (e.g., as a result of the user interacting with a display brightness slider on their phone) and / or can be automatically adjusted (e.g., based on stored preferences, brightness rules, and / or battery settings).

[0072] The temperature 214 can be determined using one or more temperature sensors that are integrated with the computing device 190. In some examples, the temperature 214 is measured by a single temperature sensor, such as a temperature sensor that measured temperature at a point of the display panel. In some examples, the temperature 214 is determined from multiple temperature sensors, such as by averaging measurements of multiple temperature sensors that each measure a temperature at a different location within the computing device 190.

[0073] The refresh rate 216 can indicate a number of times that the display updates with new content per second. Refresh rate can be specified as a value of Hertz (Hz) or frames per second (fps). The refresh rate can vary based on a power saving mode of the device 190. Power saving modes can include normal mode, low power mode, and always-on-display7(ADD) mode.

[0074] In general, the zone usage calculator 210 calculates zone usage values 218 for each of multiple zones of the display device and outputs zone usage values 218 to the bum-in compensator. The zone usage calculator calculates the zone usage values 218 for a zone based on content presented by pixels of the zone. The zone usage values 218 represent an amount of usage by pixels in the zone. The calculation of the zone usage values 218 can also be based on the DBV 212, the temperature 214, the refresh rate 216, or any combination thereof. The bum-in compensator 220 generates compensation values 222 to be applied toAttorney Docket No.: 56113-0816WO1 image data 201 through an alpha layer 224. The compensation values 222, when applied to image data 201, result in the generation of modified image data 202 that mitigates the effects of pixel bum-in. For example, the modified image 202, when presented by pixels of the display, has a more consistent brightness across the image compared to a presentation of the unmodified image data 201.

[0075] Shapes and locations of zones of display devices that are used for monitoring usage are described in greater detail with reference to FIGS. 3A to 3E. Zone usage calculations performed by the zone usage calculator 210 are described in greater detail with reference to FIGS. 4 and 5. Generation of compensation values 222 is described in greater detail with reference to FIG. 5.

[0076] In some examples, the process of generating compensation values 222 can be performed periodically (e.g., daily, semi-daily, weekly, semi-weekly). For example, the zone usage calculator 210 can monitor usage of a zone over a period of time (e.g., one week) and combine the usage of the zone with a previous cumulative zone usage for the zone to output the zone usage values 218. The bum-in compensator 220 can then generate the compensation values 222 based on the total usage of each zone up to and including the period of time. In an example, the bum-in compensator 220 generates updated compensation values 222 every Sunday morning based on zone usage values 218 calculated up through and including the previous seven days.

[0077] The processor 204 stores the compensation values 222 in the alpha layer 224. The alpha layer 224 is an overlay layer that is generated by the processor 204 of the SoC 105 and that can be used for image compensation. The alpha layer 224 can be used for alpha blending. Alpha blending is a process of combining one image with a background to create the appearance of partial or full transparency. Alpha blending is a form of encoding that can be used to render pixels in separate passes or layers and then combine the resulting images into a single, final image called the composite. Alpha blending can be used in computer graphics to put rasterized foreground elements over a background. In order to combine the pixels of the images, an associated alpha value can be kept for each pixel in addition to an intensity value for the pixel. The value of the alpha channel influences the values of the color channels. In a two-dimensional image, a color combination can be stored for each pixel, which may be a combination of red, green, and blue (RGB). When alpha blending is in use, each pixel has an additional numeric value stored in its alpha channel, e.g., with a value ranging from 0 to 1. The RGB channels of a pixel can be multiplied by the alpha value to obtain an encoded value.Attorney Docket No.: 56113-0816WO1

[0078] The processor 204 applies the compensation values 222 to the image data 201 to generate the modified image data 202. For example, the processor 204 can apply the compensation values 222 to the image data 201 by multiplying image data values by corresponding values of the compensation values 222 in the alpha layer 224. In some examples, the processor 204 applies the compensation values 222 to the image data 201 bydividing image data values by corresponding values of the compensation values 222.

[0079] As shown in FIG. 2, the image data 201 is both used by the zone usage calculator 210 to determine zone usage, and also combined with the alpha layer 224 to generate the modified image data 202 for presentation by the display device. A frame of image data 201 is thus modified using compensation values 222, which are generated from zone usage values 218 based on past usage of the display device. The zone usage values 218 calculated for a current frame of image data 201 are used for future updates to the compensation values 222 that will be applied to future frames of image data.

[0080] The SoC 105 provides display input data 102 to the DDIC 106. The display input data 102 can include the modified image data 202 generated by applying the compensation values 222 to the image data 201. Although FIG. 2 shows the SoC 105 generating the modified image data 202 from the image data 201, other implementations are possible. For example, in some implementations, the SoC 105 provides the compensation values 222 and the image data 201 to the DDIC 106, and the DDIC 106 modifies the image data 201 using the compensation values 222.

[0081] FIGS. 3A to 3E show example zones of a display device for monitoring pixel usage and for modifying content to reduce the effects of pixel bum-in. The zones can be non- uniform in shape, size, or both. Generally, the zones increase in size with distance from a center of the display device, so that inner zones that are nearer to the center are smaller than outer zones further from the center. In some examples, the zones are concentric, with an inner zone being completely surrounded by an outer zone.

[0082] FIG. 3A shows a display device 300 with multiple zones 310a to 310f. The multiple zones are used to monitor usage. The zones include a zone 310a having a rectangular shape. The zone 310a overlaps a center 311 of the display device 300. Completely surrounding the zone 310a is a zone 310b having a rectangular annulus shape (e.g., a rectangular frame shape). Completely surrounding the zone 310b is a zone 310c having a rectangular annulus shape. Zones 3 lOd- 1 and 310d-2 combined surround the zone 310c, and each have a U-shape. Zones 310e-l and 310e-2 combined surround the zones 310d-l and 310d-2, and each have a U-shape. Zones 310f-l and 310f-2 combined surround the zonesAttorney Docket No.: 56113-0816WO131 Oe-1 and 310e-2, and each have a U-shape. The zones 31 Of-1 and 310f-2 each abut an outer edge 312 around the periphery of the display device 301.

[0083] The multiple zones 310a to 31 Of are formed of different quantities of pixels that increase with distance from the center 311 of the display device 300. In other words, the multiple zones 310a to 31 Of are formed of different quantities of pixels that decrease with distance from the outer edge 312 of the display device 300. For example, the zone 310a is formed of fewer pixels than the zone 310b, and therefore occupies a smaller display area than the zone 310b, which is further from the center 311 than the zone 310a. Similarly, the zone 310b is formed of fewer pixels than the zone 310c, which is further from the center 311 than the zone 310b. In another example, the zone 310f-l is formed of more pixels than the zone 310e-l, which is nearer to the center 311 than the zone 31 Of-1. Similarly, the zone 31 Oe-1 is formed of more pixels than the zone 31 Od-I , which is nearer to the center 311 than the zone 310e-f. The zones 31 Of-1 and 310f-2 may be formed from the same or approximately same number of pixels as each other.

[0084] In some examples, the multiple zones have different heights in the y-direction that increase with distance from the center 311. For example, the zone 310a has a height in pixels that is less than a height of the zone 310b, which is further from the center 311 than the zone 310a. Similarly, the zone 310b has a height in pixels that is less than a height of the zone 310c. which is further from the center 311 than the zone 310b. In an example, the zone 310a has a height of four pixels, the zone 310b has a height of six pixels, and the zone 310c has a height of eight pixels.

[0085] In some examples, the multiple zones have different widths in the x-direction that increase with distance from the center 311. For example, the zone 310a has a width in pixels that is less than a width of the zone 310b, which is further from the center 311 than the zone 310a. Similarly, the zone 310b has a width in pixels that is less than a width of the zone 310c, which is further from the center 311 than the zone 310b. In another example, the zone 31 Of- 1 has a width in pixels that is more than a width of the zone 31 Oe-1, w hich is nearer to the center 311 than the zone 310f-l . Similarly, the zone 310e-l has a width in pixels that is more than a width of the zone 31 Od- 1. which is nearer to the center 311 than the zone 31 Oe-f. The zones 31 Of-1 and 310f-2 may have a same or approximately same width in pixels as each other. In an example, the zone 310a has a w idth of two pixels, the zone 310b has a width of four pixels, and the zone 310c has a width of six pixels.

[0086] The zone 310a includes multiple pixels. FIG. 3A includes a callout 314 showing example pixels 315 of the zone 310a. Each pixel 315 is labeled with a respective pixelAttorney Docket No.: 56113-0816WO1 intensity value. The pixel intensity values of pixels within a zone can be combined to obtain a zone intensity value. For example, the pixel intensity values can be combined by averaging. In the example of FIG. 3 A, pixel intensity values of the pixels 315 are averaged 316 to obtain a zone intensity value 318 of “123”.

[0087] FIG. 3B shows a display device 301 with multiple zones 320a to 320f. The zones includes a zone 320a having a rectangular shape. The zone 320a overlaps a center 321 of the display device 301. Completely surrounding the zone 320a is a zone 320b having a rectangular annulus shape. Similarly, a zone 320c completely surrounds the zone 320b, a zone 320d completely surrounds the zone 320c, a zone 320e completely surrounds the zone 320d, and a zone 320f completely surrounds the zone 320e. The zone 320f abuts an edge 322 of the display device 301. The number of pixels in each zone increases with distance from the center 321.

[0088] FIG. 3C shows a display device 302 with multiple zones 330a to 330d. Zones 330a-l and 330a-2 each abut a center 331 of the display device 301 and each have a rectangular shape. Zones 330b-l and 330b-2 combined surround the zones 330a-l and 330a-2 and each have a U-shape. Zones 330c-l and 330c-2 combined surround the zones 330b-l and 330b-2 and each have a U-shape. Zones 330d-l and 330d-2 combined surround the zones 330c-l and 330c-2 and each have a U-shape. The zones 330d-l and 330d-2 each abut an outer edge 332 around the periphery of the display device 302. The number of pixels in each zone increases with distance from the center 331.

[0089] FIG. 3D shows a display device 302 with multiple zones 340a to 340d. Zone 340a overlaps a center 341 of the display device 301 and has a rectangular shape. Zones 340b-l to 340b-4 combined surround the zone 340a and each have an L-shape. Zones 340c- 1 to 340c-4 combined surround the zones 340b- 1 to 340b-4 and each have an L-shape. Zones 340d-l to 340d-4 combined surround the zones 340c- 1 to 340c-4 and each have an L-shape. The zones 340d-l to 340d-4 each abut an outer edge 342 around the periphery of the display device 303. The number of pixels in each zone increases with distance from the center 341.

[0090] FIG. 3E shows a display device 304 with multiple zones 350a to 350d that each have a rectangular shape. Zone 350a- 1 overlaps a center 351 of the display device 304. Zones 350a-2 and 350a-2 abut the zone 350a-l and are a same or approximately same size as the zone 350a-l. Zones 350b-l to 350b-4 combined surround the zones 350a-l to 350a-3. Zones 350c-l to 350c-4 combined surround the zones 350b-l to 350b-4. Zones 350c-2 and 350c-4 abut an edge 352 around the periphery of the display device 304. Zones 350d-l and 350d-2Attorney Docket No.: 56113-0816WO1 are positioned at a top and bottom of the display device 304, respectively, and each abut the edge 352. The number of pixels in each zone increases with distance from the center 351.

[0091] In the examples of 3A, 3B, 3D, and 3E, borders between zones avoid crossing through the center of the display devices. This can reduce visual artifacts that may occur at borders between zones at the center of the display, where the user’s attention is most commonly focused.

[0092] FIG. 4 shows a timing diagram 400 of monitoring zone usage of a display device. The diagram 400 shows four frame samples 401, fi to ft. During each frame sample, the zone usage calculator 210 obtains an intensity value 410 for Zone A and an intensity value 414 for Zone B. The zone usage calculator 210 determines a modified intensity value 412 for Zone A and a modified intensity value 416 for Zone B based on display parameters. Display parameters can include a DBV 402, temperature 404, refresh rate 406, or any combination thereof.

[0093] Zone A and Zone B can be any two zones of the display device. For example. Zone A and Zone B can be any two zones of the display devices 300 to 304. Calculations for two zones are shown for illustration, however the zone usage calculator 210 performs zone usage calculations for all zones of the device. In some examples, the zone usage calculator 210 samples a subset of zones during each frame sample. For example, referring to FIG. 3A, during a first frame sample, the zone usage calculator 210 can sample zones 310a, 310c, 310e-l, and 310e-2. During a second frame sample, the zone usage calculator can sample zones 310b, 31 Od- 1 , 310d-2, 31 Of- 1 , and 31 Of-2.

[0094] A frame sample can be any instance of an image frame during which display pixel intensity values and / or display parameters are obtained. The zone usage calculator 210 can obtain samples continually, periodically, and / or intermittently during operation of the display device. Thus, the frame samples fi to f4 might not be immediately consecutive (e.g., time may elapse between some or all frame samples fi to ft).

[0095] At frame sample fi, the DBV 402 is 80%, the temperature is 40°F, and the refresh rate is 120 Hz. Based on the DBV 402, the temperature 404, and the refresh rate 406, the zone usage calculator 210 calculates a modification factor 408 of +6. The modification factor is a factor to apply to the zone intensity values during frame sample fi, and can be a positive or negative value.

[0096] The intensity value 410 of Zone A during frame sample fi is 123. The intensity value of Zone A can be calculated based on pixel intensity values within the zone as described with reference to FIG. 3 A. The modified intensity value 412 of Zone A is thereforeAttorney Docket No.: 56113-0816WO1123+6=129. The intensity value of Zone B during frame sample fi is 77. The modified intensity value of Zone B is therefore 77+6=83.

[0097] At frame sample fz, the DBV 402 is 80%, the temperature is 46°F, and the refresh rate is 120 Hz. Based on the DBV 402, the temperature 404, and the refresh rate 406, the zone usage calculator 210 calculates a modification factor 408 of +8. The modification factor 408 is a factor to apply to the zone intensity values during frame sample fz. The modification factor 408 for frame sample fz is greater than the modification factor 408 for frame sample fi due to the higher temperature resulting in a greater effective usage of pixels, at the same refresh rate and DBV.

[0098] The intensity value 410 of Zone A during frame sample f2 is 102. The modified intensity value 412 of Zone A is therefore 102+8=110. The intensity value of Zone B during frame sample fz is 207. The modified intensity value of Zone B is therefore 207+8=215.

[0099] At frame sample fi. the DBV 402 is 60%, the temperature is 46°F, and the refresh rate is 60 Hz. Based on the DBV 402, the temperature 404, and the refresh rate 406, the zone usage calculator 210 calculates a modification factor 408 of +3. The modification factor 408 is a factor to apply to the zone intensity values during frame sample fi. The modification factor 408 for frame sample fi is less than the modification factor 408 for frame samples fi and fi due to the reduced DBV and reduced refresh rate resulting in a lesser effective usage of pixels.

[0100] The intensity value 410 of Zone A during frame sample fi is 80. The modified intensity value 412 of Zone A is therefore 80+3=83. The intensity value of Zone B during frame sample fz is 141. The modified intensity' value of Zone B is therefore 141+3=144.

[0101] At frame sample ft, the DBV 402 is 60%, the temperature is 46°F, and the refresh rate is 1 Hz. Based on the DBV 402. the temperature 404. and the refresh rate 406, the zone usage calculator 210 calculates a modification factor 408 of -1. The modification factor 408 is a factor to apply to the zone intensity values during frame sample ft The modification factor 408 for frame sample fi is less than the modification factor 408 for frame samples fi to fi due to the reduced refresh rate resulting in a lesser effective usage of pixels.

[0102] The intensity value 410 of Zone A during frame sample ft is 206. The modified intensity value 412 of Zone A is therefore 206-1=205. The intensity value of Zone B during frame sample ft is 108. The modified intensity' value of Zone B is therefore 108-1=107.

[0103] The modified intensity values 412 for Zone A are input to a histogram 420 for Zone A. The histogram 420 includes modified intensity values for pixels of a same color within Zone A. In some examples, the zone usage calculator 210 generates a separateAttorney Docket No.: 56113-0816WO1 histogram for each individual color channel. In some examples, the zone usage calculator 210 generates a single histogram for all color channels in a zone.

[0104] The histogram 420 represents a number of calculated intensity values that fall into each of multiple ’‘buckets.” Each bucket is shown as a bar of the histogram 420, where a height of the bar represents a number of instances of the intensity value. In some examples, each bucket represents an integer intensity value between 0 and 255, such that the total number of buckets is 256. In some examples, each bucket represents a range of integer intensity values (e.g., 0 to 2, 3 to 5). Each time a particular intensity value is calculated by the zone usage calculator 210 for Zone A, the histogram 420 is incremented by +1 for the associated bucket. For example, as a result of calculating the modified intensity values for Zone A for frames fi to ft, the histogram 420 is updated to add +1 to each of the buckets for intensity values 129, 1 10, 83, and 205.

[0105] Similar to Zone A, the modified intensity values 416 for Zone B are input to a histogram 430 for Zone B. As a result of calculating the modified intensity values for Zone B for frames fi to fi, the histogram 430 is updated to add +1 to each of the buckets for intensity values 83, 215, 144, and 107.

[0106] The histograms 420, 430 can each be updated over a sampling period (e.g., one day, one week) such that the histograms 420, 430 represent the distributions of modified intensity values in the Zones A and B, respectively, over sampling period. The histograms 420, 430 can then be used to update zone usage values of Zones A and B based on usage during the period of time, as will be described in greater detail with reference to FIG. 5 A. After the histogram 420 is used to update the zone usage value, the histogram 420 can be reset so that all of the buckets are at zero, and the process of calculating zone intensity values can begin again.

[0107] FIG. 4 illustrates an example in which individual intensity values are modified to account for effects of changing display parameters including DBV 402, temperature 404, and refresh rate 406. In some examples, effects of changing display parameters can instead be accounted for by modifying combined zone intensity values. For example, during a time period when display parameters are steady at a set of first display parameter values, intensityvalues 410 for Zone A can be tallied in a first histogram. One or more display parameters may then change to a second set of display parameter values. Intensity values can then begin to be tallied in a second histogram. The first histogram can be modified based on the first set of display parameter values to account for adjusted usage. The second histogram can be modified based on the second set of display parameters. At the end of a sampling period (e.g.,Attorney Docket No.: 56113-0816WO1 one day, one week), the zone usage for the zone can be determined based on the multiple adjusted histograms for Zone A.

[0108] FIG. 5 A shows example calculations of total zone usage for multiple zones. The zone usage calculator 210 can maintain a running zone usage value over time and can update the zone usage based on the modified zone intensity values determined as described with reference to FIG. 4.

[0109] For Zone A, a previous zone usage 502 is 4250 hrs. The previous zone usage 502 can be a running total of usage for the Zone A determined from previous zone intensity calculations. After obtaining zone intensity values for a new sampling period, the zone usage calculator 210 can determine a new zone usage 504 from the histogram 420 for Zone A. The new zone usage can represent an effective amount of usage caused to the pixels based on the distribution of the zone intensity levels in the histogram 420. In the example of FIG. 5A, usage is represented in hours. Other units of measurement can be used, such as other measurements of time (e.g., minutes, days, years).

[0110] For Zone A, the previous zone usage 502 is 4250 hours, and the new zone usage 504 determined from the histogram 420 is 18 hours. The total zone usage is therefore 4250+18=4268 hours. For Zone B, the previous zone usage 502 is 9284 hours, and the new zone usage 504 determined from the histogram 430 is 26 hours. The total zone usage is therefore 9284+26=9310 hours.

[0111] FIG. 5B shows an example graph 511 including a curve 515 representing zone efficiency 512 vs. total zone usage 506. The graph 51 1 shows a decrease in zone efficiency 512 with increased zone usage 506. The graph 511 can be used to determine an expected zone efficiency from a calculation of total zone usage 506.

[0112] For example, the total zone usage 506 for Zone A. 4250 hours, can be plotted on the graph 511 to identify a point of intersection 520 with the curve 515. The point of intersection 520 is at a zone efficiency 512 of approximately 91%. Thus, the expected zone efficiency of Zone A after 4250 hours of zone usage is approximately 91%. Similarly, the total zone usage 506 for Zone B. 9310 hours, can be plotted on the graph 511 to identify a point of intersection 530 with the curve 515. The point of intersection 530 is at a zone efficiency 512 of approximately 88%. Thus, the expected zone efficiency of Zone B after 9310 hours of zone usage is approximately 88%.

[0113] The curve 515 may be different for different colored pixels. For example, some colored pixels may decay at different rates than other colored pixels. The zone usageAttorney Docket No.: 56113-0816WO1 calculator 210 and / or the bum-in compensator 220 determines the zone efficiency 512 using the appropriate curve 515 for the pixel color.

[0114] The zone efficiency 512 can be used to generate compensation values 222. For example, the bum-in compensator can generate compensation values 222 for each zone based on the zone efficiencies of each zone. In some examples, the bum-in compensator 220 identifies a most-used zone of the multiple zones of the display device. The bum-in compensator 220 can generate compensation values 222 to dim zones other than the most- used zone to limit a maximum luminance of the other zones to the maximum luminance of the most-used zone. In the simplified example of FIG. 5B, Zone B is the most-used zone due to having a greater total zone usage 506 than Zone A. Therefore, compensation values 222 can be generated that modify image data provided to Zone A such that the maximum luminance of Zone A is limited to the maximum luminance of Zone B.

[0001] In some examples, the bum-in compensator 220 determines a difference between usage of a zone and usage of a neighboring zone. A neighboring zone is a zone that is directly adjacent to another zone. For example, referring to FIG. 3B, the zone 320b is a neighboring zone of the zone 320a and of the zone 320c. The zone 320c is a neighboring zone of the zone 320b and of the zone 320d. The bum-in compensator 220 can identify, for any set of two neighboring zones, a more-used zone and a lesser-used zone. The bum-in compensator 220 can generate compensation values 222 to dim the lesser-used zone to reduce the difference between luminance of the lesser-used zone and the more-used zone. In some examples, processor 204 repeats the process of determining zone usage values 218 and generating compensation values 222 for multiple sets of neighboring zones. For example, the processor 204 can generate compensation values 222 for reducing the difference in luminance between the zone 320a and the zone 320b, and can generate compensation values 222 for reducing the difference in luminance between the zones 320b and the zone 320c.

[0002] In some examples, the bum-in compensator 220 compares a difference between usage of neighboring zones to a threshold difference. The bum-in compensator can determine to generate the compensation values in response to determining that the difference between usage of neighboring zones exceeds the threshold difference. The compensation values can dim the luminance of the lesser-used zone to reduce the difference between luminance of the lesser-used zone and luminance of the more-used zone.

[0003] In some examples, the bum-in compensator 220 generates compensation values 222 that limit a maximum luminance of the lesser-used zone to the maximum luminance of the more-used zone. In the simplified example of FIG. 5B, Zone A and Zone B may beAttorney Docket No.: 56113-0816WO1 neighboring zones. Zone B is the more-used zone due to having a greater total zone usage 506 than Zone A. Therefore, compensation values 222 can be generated that modify image data provided to Zone A such that the difference between luminance of Zone A and luminance of Zone B is reduced.

[0115] FIG. 6 shows a flowchart of a process 600 for operating a display device with pixel bum-in compensation. The process may be implemented by a display device or a computing device that includes the display device.

[0116] A computing system receives display content. For example, the computing device 190 described with respect to FIG. 1 can receive image data 201, including display content for presentation on the display panel 104 of the device 190. The display content can include a series of frames of image data for presentation by the display panel 104, for example, before modification of the frames to compensate for display bum-in.

[0117] At box 610, the computing system identifies multiple zones of a display device for which to monitor pixel usage. Each zone of the multiple zones is formed of a corresponding group of multiple pixels. The multiple zones are formed of different quantities of pixels that increase with distance from a center of the display device, such that a first zone of the multiple zones is formed of fewer pixels than a second zone of the multiple zones that is further from the center of the display device than the first zone. For example, referring to FIG. 3E, the zone 350a-l is formed of fewer pixels than the zone 350b-l. which is further from the center 351 than the zone 350a-l. Similarly, the zone 350b-l is formed of fewer pixels than the zone 350d- 1 , which is further from the center 351 than the zone 350b-l .

[0118] In some examples, a height of the second zone is greater than a height of the first zone. For example, referring to FIG. 3C, a first zone 330a-l has a height in pixels in the y-direction that is less than a height of a second zone 330b-l, which is further from the center 331 than the first zone 330a-l.

[0119] In some examples, a width of the second zone is greater than a width of the first zone. For example, referring to FIG. 3B, a first zone 320a has a width in pixels in the x-direction that is less than a width of a second zone 320b, which is further from the center 321 than the first zone 320a.

[0120] In some examples, the second zone completely surrounds the first zone. For example, referring to FIG. 3B, a second zone 320b completely surrounds a first zone 320a.

[0121] In some examples, the multiple zones include a third zone that is further from the center of the display device than both the second zone and the first zone. The third zone can be formed of more pixels than both the second zone and the first zone. A height of the thirdAttorney Docket No.: 56113-0816WO1 zone can be greater than both the height of the first zone and the height of the second zone. A width of the third zone can be greater than both the width of the first zone and the width of the second zone. For example, referring to FIG. 3C, a third zone 330c- 1 is further from the center 331 than both a second zone 330b-l and a first zone 330a-l. The third zone 330c-l is formed of more pixels than both the second zone 330b- 1 and the first zone 330a-l. The third zone 330c-l has a height in pixels that is greater than both the height of the second zone 330b-l and the first zone 330a-l. The third zone 330c- 1 has a width in pixels that is greater than both the width of the second zone 330b-l and the first zone 330a-l.

[0122] At box 620, the computing system determines zone usage values for each of the multiple zones. The computing system determines a usage value for each zone based on content presented by the zone. Determining the zone usage can include combining pixel intensity values to form an initial zone intensity value (622) For example, the computing system determines the intensity value that represents the intensity of content presented by pixels of the zone, by combining multiple pixel values for pixels of the zone into a single value. Combining the multiple pixel values for pixels of the zone into the single value can include averaging the multiple pixel values. For example, referring to FIG. 3A. pixel intensity values for the pixels 315 are averaged to determine a zone intensity value 318. In some examples, the pixels of the zone for which the multiple pixel values are combined are adapted to present a same color channel.

[0123] In some examples, the computing system updates a histogram that is specific to the zone by adding to the histogram an intensity value that represents an intensity of content presented by the zone, repeatedly for different presentations of content by the zone at different times. The computing system determines the zone usage value based on intensity values of the histogram that is specific to the zone. For example, referring to FIG. 4, the computing system can determine the zone usage value based on intensity values of the histogram 420 that is specific to Zone A.

[0124] In some examples, determining the zone usage values includes modiy ing the initial zone intensity value based on display parameters to form a modified zone intensify’ value (624). For example, referring to FIG. 4. intensity values are modified by a modification factor 408 determined based on display parameters.

[0125] In some examples, the computing device combines intensify' values that represent an intensity of content presented by pixels of the zone at different times with data that indicates different temperatures of the display device at the different times, to generate modified zone intensity values. For example, referring to FIG. 4, the modification factor 408Attorney Docket No.: 56113-0816WO1 is based at least in part on temperature 404 measured during each of the respective frame samples. The modified zone intensity values can be used to generate the usage value for the zone, such that the usage value for the zone accounts for increased usage that results from outputting content at increased temperatures.

[0126] In some examples, the computing device combines intensity values that represent an intensity of content presented by pixels of the zone at different times with data that indicates different refresh rates of the display device at the different times, to generate modified zone intensity values. For example, referring to FIG. 4, the modification factor 408 is based at least in part on refresh rate 406 during each of the respective frame samples. The modified zone intensity values can be used to generate the usage value for the zone, such that the usage value for the zone accounts for both intensities of presented content and refresh rates.

[0127] In some examples, the computing device combines intensity values that represent an intensity of content presented by pixels of the zone at different times with data that indicates different overall display brightness values of the display device at the different times, to generate a modified zone intensity value. For example, referring to FIG. 4, the modification factor 408 is based at least in part on DBV 402 during each of the respective frame samples. The modified zone intensity7values can be used to generate the usage value for the zone, such that the usage value for the zone accounts for both intensities of presented content and overall display brightness values.

[0128] Determining the zone usage values includes updating the zone usage value based on one or more modified zone intensity values (626). For example, referring to FIG. 5A, the total zone usage 506 is updated by adding the new zone usage 504 to previous zone usage 502.

[0129] At box 630, the computing system determines a most-used zone of the multiple zones. The computing system determines the most-used zone based on the usage value for the most-used zone representing a greatest amount of usage among the multiple zones. For example, referring to FIG. 5B, the computing system determines that Zone B is the most-used zone based on the total zone usage of 9310 representing the greatest amount of usage (e.g.. greater than the total zone usage of 4268 for Zone A).

[0130] At box 640, the computing system modifies an output sent to pixels of the display device based on the zone usage values and the determination of the most-used zone. The computing system modifies the output sent to the pixels of the display device to reduce effects of pixel bum-in, for example, so that a particular pixel intensity value (e.g., 155 out ofAttomey Docket No.: 56113-0816WO1255) is presented with a same brightness when presented by pixels in different zones with different amounts of bum-in.

[0131] Modifying the output can include modifying output sent to pixels of other zones of the multiple zones other than the most-used zone, to dim content presented by the other zones and limit a maximum luminance of the other zones to a maximum luminance of the most-used zone. In some examples, the computing system modifies the output to dim content presented by the other zones a proportional amount based on the differences between the usage values for the other zones and the usage value for the most-used zone. For example, referring to FIG. 5B, based on the zone usage values for Zones A and B, the zone efficiency for Zone A is determined to be 91% and the zone efficiency for Zone B is determined to be 88%. Therefore, Zone B is the most-used zone, and Zone A is the other zone. Output to pixels of Zone A can be modified to dim content presented by the pixels of Zone A by a proportional amount (e.g., to dim the content by 3% from the original 100% intensify, which corresponds to a reduction in luminance of about 3.3% from a luminance of content when presented at 91% efficiency). A third example zone, Zone C (not shown) may have a calculated zone efficiency of 98%. and output to pixels of Zone C can be modified to dim content presented by the pixels of Zone C by a proportional amount (e g., to dim content by 10% from the original 100% intensify7, which corresponds to a reduction in luminance of about 10.2% from a luminance of content when presented at 98% efficiency).

[0132] In some examples, the amount of dimming applied to each zone is the same regardless of content presented by the zone, such that all content presented by a zone is dimmed the same amount (e.g., such that bright and dark content presented by Zone A are both dimmed 3.3%). In some examples, the content dimming is based on a brightness of content to be presented by the zone (e.g., such that bright content presented by Zone A is dimmed 3.3% and dark content presented by Zone A is dimmed 2.1%). The computing system may store data that represents dimming curves, which can be used to determine an amount to dim content that to be presented by a zone, based on: (i) an amount of dimming to apply to entirely bright content presented by the zone (e.g., with all pixels presenting intensify values of 255 out of 255), and (ii) an intensify of content to be presented by the zone (e.g., with an average intensify7of content in the zone being 142 out of 255).

[0133] In some examples, modifying the output includes modifying output sent to pixels of inner zones to dim content presented by the inner zones and limit a maximum luminance of the inner zones to intensities that are greater than the maximum luminance of the most- used zone. An inner zone is a zone that is closer to the center of the display than the most-Attorney Docket No.: 56113-0816WO1 used zone. In this way, zones outside of the most-used zone can be limited to a maximum brightness of the most-used zone, while zones inside the most-used zone can be dimmed but with a maximum intensity that is brighter than the most-used zone.

[0134] FIG. 7 is a block diagram of computing devices 700, 750 that may be used to implement the systems and methods described in this document, as either a client or as a server or plurality of servers. Computing device 700 is intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. Computing device 750 is intended to represent various forms of mobile devices, such as personal digital assistants, cellular telephones, smartphones, and other similar computing devices. The components shown here, their connections and relationships, and their functions, are meant to be examples only, and are not meant to limit implementations described and / or claimed in this document.

[0135] Computing device 700 includes a processor 702, memory 704, a storage device 706, a high-speed controller 708 connecting to memory 704 and high-speed expansion ports 710, and a low speed controller 712 connecting to low speed expansion port 714 and storage device 706. Each of the components 702, 704, 706, 708, 710, and 712, are interconnected using various busses, and may be mounted on a common motherboard or in other manners as appropriate. The processor 702 can process instructions for execution within the computing device 700, including instructions stored in the memory 704 or on the storage device 706 to display graphical information for a GUI on an external input / output device, such as display 716 coupled to high-speed controller 708. In other implementations, multiple processors and / or multiple buses may be used, as appropriate, along with multiple memories and types of memory. Also, multiple computing devices 700 may be connected, with each device providing portions of the necessary operations (e.g., as a server bank, a group of blade servers, or a multi-processor system).

[0136] The memory7704 stores information within the computing device 700. In one implementation, the memory 704 is a volatile memory7unit or units. In another implementation, the memory 704 is a non-volatile memory unit or units. The memory 704 may also be another form of computer-readable medium, such as a magnetic or optical disk.

[0137] The storage device 706 is capable of providing mass storage for the computing device 700. In one implementation, the storage device 706 may be or contain a computer- readable medium, such as a floppy disk device, a hard disk device, an optical disk device, or a tape device, a flash memory or other similar solid state memory device, or an array ofAttorney Docket No.: 56113-0816WO1 devices, including devices in a storage area network or other configurations. A computer program product can be tangibly embodied in an information carrier. The computer program product may also contain instructions that, when executed, perform one or more methods, such as those described above. The information carrier is a computer- or machine-readable medium, such as the memory' 704, the storage device 706, or memory' on processor 702.

[0138] The high-speed controller 708 manages bandwidth-intensive operations for the computing device 700. while the low speed controller 712 manages lower bandwidthintensive operations. Such allocation of functions is an example only. In one implementation, the high-speed controller 708 is coupled to memory' 704, display 716 (e.g., through a graphics processor or accelerator), and to high-speed expansion ports 710, which may accept various expansion cards (not shown). In the implementation, low-speed controller 712 is coupled to storage device 706 and low-speed expansion port 714. The low-speed expansion port, which may include various communication ports (e.g., USB, Bluetooth, Ethernet, wireless Ethernet) may be coupled to one or more input / output devices, such as a keyboard, a pointing device, a scanner, or a networking device such as a switch or router, e.g.. through a network adapter.

[0139] The computing device 700 may be implemented in a number of different forms, as show n in the figure. For example, it may be implemented as a standard server 720, or multiple times in a group of such servers. It may also be implemented as part of a rack server system 724. In addition, it may be implemented in a personal computer such as a laptop computer 722. Alternatively, components from computing device 700 may be combined with other components in a mobile device (not shown), such as device 750. Each of such devices may contain one or more of computing device 700, 750, and an entire system may be made up of multiple computing devices 700, 750 communicating with each other.

[0140] Computing device 750 includes a processor 752, memory 764, an input / output device such as a display 754, a communication interface 766, and a transceiver 768, among other components. The device 750 may also be provided with a storage device, such as a microdrive or other device, to provide additional storage. Each of the components 750, 752, 764, 754. 766, and 768, are interconnected using various buses, and several of the components may be mounted on a common motherboard or in other manners as appropriate.

[0141] The processor 752 can execute instructions within the computing device 750, including instructions stored in the memory 764. The processor may be implemented as a chipset of chips that include separate and multiple analog and digital processors.Additionally, the processor may be implemented using any of a number of architectures. For example, the processor may be a CISC (Complex Instruction Set Computers) processor, aAttorney Docket No.: 56113-0816WO1RISC (Reduced Instruction Set Computer) processor, or a MISC (Minimal Instruction Set Computer) processor. The processor may provide, for example, for coordination of the other components of the device 750, such as control of user interfaces, applications run by device 750, and wireless communication by device 750.

[0142] Processor 752 may communicate with a user through control interface 758 and display interface 756 coupled to a display 754. The display 754 may be, for example, a TFT (Thin-Film-Transistor Liquid Crystal Display) display or an OLED (Organic Light Emitting Diode) display, or other appropriate display technology. The display interface 756 may comprise appropriate circuitry for driving the display 754 to present graphical and other information to a user. The control interface 758 may receive commands from a user and convert them for submission to the processor 752. In addition, an external interface 762 may be provided in communication with processor 752, so as to enable near area communication of device 750 with other devices. External interface 762 may be provided, for example, for wired communication in some implementations, or for wireless communication in other implementations, and multiple interfaces may also be used.

[0143] The memory 764 stores information within the computing device 750. The memory 764 can be implemented as one or more of a computer-readable medium or media, a volatile memory unit or units, or a non-volatile memory' unit or units. Expansion memory' 774 may also be provided and connected to device 750 through expansion interface 772, which may include, for example, a SIMM (Single In Line Memory Module) card interface. Such expansion memory' 774 may provide extra storage space for device 750, or may also store applications or other information for device 750. Specifically, expansion memory' 774 may include instructions to carry out or supplement the processes described above, and may include secure information also. Thus, for example, expansion memory 774 may be provided as a security module for device 750, and may be programmed with instructions that permit secure use of device 750. In addition, secure applications may be provided via the SIMM cards, along with additional information, such as placing identifying information on the SIMM card in a non-hackable manner.

[0144] The memory may include, for example, flash memory and / or NVRAM memory, as discussed below. In one implementation, a computer program product is tangibly embodied in an information carrier. The computer program product contains instructions that, when executed, perform one or more methods, such as those described above. The information carrier is a computer- or machine-readable medium, such as the memory 764,Attorney Docket No.: 56113-0816WO1 expansion memory 774, or memory on processor 752 that may be received, for example, over transceiver 768 or external interface 762.

[0145] Device 750 may communicate wirelessly through communication interface 766, which may7include digital signal processing circuitry where necessary. Communication interface 766 may provide for communications under various modes or protocols, such as GSM voice calls, SMS, EMS, or MMS messaging, CDMA. TDMA, PDC, WCDMA, CDMA2000. or GPRS, among others. Such communication may occur, for example, through radio-frequency transceiver 768. In addition, short-range communication may occur, such as using a Bluetooth, WiFi, or other such transceiver (not shown). In addition, GPS (Global Positioning System) receiver module 770 may provide additional navigation- and location- related wireless data to device 750, which may be used as appropriate by applications running on device 750.

[0146] Device 750 may also communicate audibly using audio codec 760, which may receive spoken information from a user and convert it to usable digital information. Audio codec 760 may likewise generate audible sound for a user, such as through a speaker, e.g., in a handset of device 750. Such sound may include sound from voice telephone calls, may include recorded sound (e.g., voice messages, music files, etc.) and may also include sound generated by applications operating on device 750.

[0147] The computing device 750 may be implemented in a number of different forms, as shown in the figure. For example, it may be implemented as a cellular telephone 780. It may also be implemented as part of a smartphone 782, personal digital assistant, tablet, or other similar mobile device.

[0148] Additionally computing device 700 or 750 can include Universal Serial Bus (USB) flash drives. The USB flash drives may store operating systems and other applications. The USB flash drives can include input / output components, such as a wireless transmitter or USB connector that may7be inserted into a USB port of another computing device.

[0149] Various implementations of the systems and techniques described here can be realized in digital electronic circuitry7, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and / or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.Attorney Docket No.: 56113-0816WO1

[0150] These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and / or object-oriented programming language, and / or in assembly / machine language. As used herein, the terms “machine-readable medium” “computer-readable medium” refers to any computer program product, apparatus and / or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and / or data to a programmable processor.

[0151] To provide for interaction with a user, the systems and techniques described here can be implemented on a computer having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and a keyboard and a pointing device (e.g., a mouse or a trackball) by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0152] The systems and techniques described here can be implemented in a computing system that includes a back end component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front end component (e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such back end, middleware, or front end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication netw ork). Examples of communication networks include a local area network (“LAN”), a wide area network (“WAN”), peer-to-peer networks (having ad-hoc or static members), grid computing infrastructures, and the Internet.

[0153] The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication net ork. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

[0154] Although a few implementations have been described in detail above, other modifications are possible. Moreover, other mechanisms for performing the systems andAttorney Docket No.: 56113-0816WO1 methods described in this document may be used. In addition, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.

Claims

Attorney Docket No.: 56113-0816WO1WHAT IS CLAIMED IS:

1. A method to reduce effects of display bum-in, comprising: identifying, by a computing device, multiple zones of a display device for which to monitor usage, with each zone of the multiple zones being formed of a corresponding group of multiple pixels, wherein the multiple zones are formed of different quantities of pixels that increase with distance from a center of the display device, such that a first zone of the multiple zones is formed of fewer pixels than a second zone of the multiple zones that is further from the center of the display device than the first zone; determining, by a computing device, multiple usage values for the multiple zones of the display device, by determining, for each zone of the multiple zones, a usage value based on content presented by pixels of the zone; determining, by the computing device, a most-used zone of the multiple zones based on the usage value for the most-used zone representing a greatest amount of usage among the multiple zones; and modifying, by the computing device based on having determined the most-used zone and the multiple usage values for the multiple zones, an output sent to pixels of the display device to reduce effects of pixel bum-in.

2. The method of claim 1, wherein determining the multiple usage values for the multiple zones of the display device includes, for each zone of the multiple zones: updating a histogram that is specific to the zone by adding to the histogram an intensity value that represents an intensity of content presented by pixels of the zone, repeatedly for different presentations of content by pixels of the zone at different times; and determining the usage value for the zone based on intensify values of the histogram that is specific to the zone.

3. The method of claim 2, comprising: determining the intensify value that represents the intensify of content presented by pixels of the zone, by combining multiple pixel values for pixels of the zone into a single value.Attorney Docket No.: 56113-0816WO14. The method of claim 3, wherein combining the multiple pixel values for pixels of the zone into the single value includes averaging the multiple pixel values.

5. The method of claim 4, wherein the pixels of the zone for which the multiple pixel values are combined are adapted to present a same color channel.

6. The method of claim 1 , wherein: the multiple zones include a third zone that is further from the center of the display device than both the second zone and the first zone; and the third zone is formed of more pixels than both the second zone and the first zone.

7. The method of claim 6, wherein: the first zone has a first height in pixels; the second zone has a second height in pixels, the second height being greater than the first height; and the third zone has a third height in pixels, the third height being greater than both the second height and the first height.

8. The method of claim 7, wherein: the first zone has a first width in pixels; the second zone has a second width in pixels, the second width being greater than the first width; and the third zone has a third width in pixels, the third width being greater than both the second width and the first width.

9. The method of claim 1 , wherein: the second zone completely surrounds the first zone.

10. The method of claim 1, wherein: the first zone has a rectangle shape; and the second zone has an “L” or “U"’ shape.Attorney Docket No.: 56113-0816WO111. The method of claim 1, wherein determining the multiple usage values for the multiple zones of the display device includes, for each zone of the multiple zones: combining intensity values that represent an intensity of content presented by pixels of the zone at different times with data that indicates different temperatures of the display device at the different times, to generate the usage value for the zone, such that the usage value for the zone accounts for increased usage that results from outputting content at increased temperatures.

12. The method of claim 1, wherein determining the multiple usage values for the multiple zones of the display device includes, for each zone of the multiple zones: combining intensity values that represent an intensity of content presented by pixels of the zone at different times with data that indicates different refresh rates of the display device at the different times, to generate the usage value for the zone, such that the usage value for the zone accounts for both intensities of presented content and refresh rates.

13. The method of claim 1, wherein determining the multiple usage values for the multiple zones of the display device includes, for each zone of the multiple zones: combining intensity values that represent an intensity' of content presented by pixels of the zone at different times with data that indicates different overall displaybrightness values for the display device at the different times, to generate the usage value for the zone, such that the usage value for the zone accounts for both intensities of presented content and overall display brightness values.

14. The method of claim 1, wherein modifying the output sent to the pixels of the display device to reduce effects of pixel bum-in includes: modify ing the output sent to pixels of other zones of the multiple zones other than the most-used zone, to dim content presented by the other zones and limit a maximum luminance of the other zones to a maximum luminance of the most-used zone.

15. The method of claim 14, wherein: inner zones are zones of the multiple zones that are closer to the center of the display device than the most-used zone; the other zones represent zones of the multiple zones other than the most-used zone and the inner zones; andAttorney Docket No.: 56113-0816WO1 modifying the output sent to the pixels of the display device to reduce effects of pixel bum-in includes modifying the output sent to pixels of the inner zones to dim content presented by the inner zones and limit a maximum luminance of the inner zones to intensities that are greater than the maximum luminance of the most-used zone.

16. The method of claim 1, wherein modifying the output sent to the pixels of the display device to reduce effects of pixel bum-in, includes: modify ing the output sent to pixels of other zones of the multiple zones other than the most-used zone, to dim content presented by the other zones a proportional amount based on differences between the usage values for the other zones and the usage value for the most-used zone.

17. The method of claim 1, wherein the multiple zones of the display device comprise a subset of all zones of the display device.

18. The method of claim 1, wherein the multiple zones of the display device comprise two neighboring zones of the display device.

19. The method of claim 1, wherein the multiple zones comprise a first set of multiple zones, the method comprising: identify ing, by the computing device, a second set of multiple zones of the display device for which to monitor usage, with each zone of the second set of multiple zones being formed of a corresponding group of multiple pixels; determining, by the computing device, a second set of multiple usage values for the second set of multiple zones of the display device, by determining, for each zone of the second set of multiple zones, a usage value based on content presented by pixels of the zone; determining, by the computing device, a most-used zone of the second set of multiple zones; and modifying, by the computing device based on having determined the most-used zone and the second set of multiple usage values for the second set of multiple zones, a second output sent to pixels of the display device to reduce effects of pixel bum-in.

20. A computing device, comprising: one or more processors; andAttorney Docket No.: 56113-0816WO1 one or more storage devices including instructions, that when executed by the one or more processors, cause the computing device to perform operations that include: identifying, by the computing device, multiple zones of a display device for which to monitor usage, with each zone of the multiple zones being formed of a corresponding group of multiple pixels, wherein the multiple zones are formed of different quantities of pixels that increase with distance from a center of the display device, such that a first zone of the multiple zones is formed of fewer pixels than a second zone of the multiple zones that is further from the center of the display device than the first zone; determining, by a computing device, multiple usage values for the multiple zones of the display device, by determining, for each zone of the multiple zones, a usage value based on content presented by pixels of the zone; determining, by the computing device, a most-used zone of the multiple zones based on the usage value for the most-used zone representing a greatest amount of usage among the multiple zones; and modifying, by the computing device based on having determined the most-used zone and the multiple usage values for the multiple zones, an output sent to pixels of the display device to reduce effects of pixel bum-in.

21. The computing device of claim 20, wherein determining the multiple usage values for the multiple zones of the display device includes, for each zone of the multiple zones: updating a histogram that is specific to the zone by adding to the histogram an intensity value that represents an intensity of content presented by pixels of the zone, repeatedly for different presentations of content by pixels of the zone at different times; and determining the usage value for the zone based on intensity values of the histogram that is specific to the zone.

22. The computing device of claim 21, the operations comprising: determining the intensity value that represents the intensity of content presented by pixels of the zone, by combining multiple pixel values for pixels of the zone into a single value.

23. The computing device of claim 22, wherein combining the multiple pixel values for pixels of the zone into the single value includes averaging the multiple pixel values.

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