Brightness control for under-display sensors

Abstract

Disclosed are methods, systems and apparatus, including a computer program encoded on a computer storage medium, for brightness control for an under-display fingerprint sensor. The method includes receiving, at a computing device, an instruction to activate an under-display sensor located under a display of the computing device, and activating a collection of LEDs of the display to provide illumination to the under-display sensor, where activating the collection of LEDs includes a drive circuit for the LEDs activating LEDs in the collection of LEDs by establishing a first overdrive voltage on an LED drive transistor adapted to energize the LEDs, establishing a second overdrive voltage on the LED drive transistor, and establishing a steady-state voltage on the LED drive transistor, and the method further includes activating the under-display sensor by reading a signal from the under-display sensor at a time when the collection of LEDs is activated, including when the steady-state voltage is programmed into the LED drive transistor.

Description

[Technical Field]

[0001] Technical Field FIELD OF THE INVENTION This specification relates generally to electronic devices having a display panel and a sensor positioned below the display panel. [Background technology]

[0002] background An electronic device may include a display panel capable of displaying visual images thereon. A sensor may be located below the display panel. For example, a fingerprint sensor may be located below a portion of the display panel. When a user places a finger on that portion of the display panel, the fingerprint sensor captures an image of the fingerprint. Summary of the Invention [Means for solving the problem]

[0003] overview A brightness control technique for an under-display sensor is disclosed. A fingerprint sensor can be positioned below a display panel of a computing device. The fingerprint sensor can be positioned below the display panel so that the width of the device's bezel is reduced because the bezel no longer needs to accommodate the fingerprint sensor. Therefore, placing the fingerprint sensor below the display panel can increase the screen-to-body ratio of the device. Furthermore, by placing the fingerprint sensor below the display, the presence of a notch in the display can be avoided.

[0004] An under-display fingerprint sensor captures photons of light generated by pixels of a display panel and reflected from a finger placed on the display panel. The fingerprint sensor may include an array of sensor sites. The sensor sites of the fingerprint sensor capture photons for a duration called the integration time. When activating the under-display fingerprint sensor, pixels of the display positioned above the under-display sensor are changed from a lower brightness to a higher brightness. Increasing the pixel intensity to a higher brightness reduces the required integration time of the fingerprint sensor.

[0005] An under-display fingerprint sensor begins integration once the pixel has stabilized at high brightness. A stabilization time is used to increase the light intensity from the previous intensity level to a higher intensity level preferred for fingerprint sensor operation. The stabilization time can last for multiple frame times, e.g., 2 frame times, 3 frame times, 4 frame times, etc.

[0006] The techniques of this disclosure can be used to reduce the stabilization time of pixels in displays with under-display sensors, which reduces the overall time between fingerprint contact detection and fingerprint authentication.

[0007] The settling time of a pixel at high brightness can be reduced by providing data voltage compensation or power supply voltage compensation to the pixel circuit. Both data voltage compensation and power supply voltage compensation involve establishing an overdrive voltage on the pixel's drive transistor to increase the current through the pixel's OLED compared to the current that would flow through the OLED if the voltage were not overdriven. Data voltage compensation achieves the overdrive voltage by adjusting the data voltage signal (VDATA) supplied to the pixel circuit. Power supply voltage compensation achieves the overdrive voltage by adjusting the power supply voltage signal (ELVDD) supplied to the pixel circuit.

[0008] Although described in this disclosure as a fingerprint sensor, the techniques of this disclosure are applicable to any passive optical sensor positioned below or adjacent to a display panel, which may include, for example, an under-display camera, an ambient light sensor, and / or other types of under-display sensors.

[0009] As further explanation of the embodiments described below, the present disclosure describes the following embodiments.

[0010] Embodiment 1 is directed to a method implemented by an electronic apparatus, the method including receiving, at a computing device, an instruction to activate an under-display sensor positioned under a display of the computing device; and activating a collection of LEDs of the display to provide illumination to the under-display sensor, wherein activating the collection of LEDs includes activating an LED in the collection of LEDs, wherein a drive circuit of the LEDs establishes, in a first programming stage of the drive circuit, a first overdrive voltage between a gate terminal of an LED drive transistor adapted to conduct electricity to the LED and a source terminal of the LED drive transistor, the first overdrive voltage being a first overdrive voltage that exceeds a steady-state voltage; and, in a second programming stage of the drive circuit subsequent to the first programming stage, the drive circuit of the LED establishes, between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor, a second overdrive voltage that exceeds the steady-state voltage and is lower than the first overdrive voltage. and the drive circuit for the LEDs establishes the steady-state voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor in a steady-state programming phase of the drive circuit subsequent to the first programming phase and the second programming phase, the method further including activating the under-display sensor by reading a signal from the under-display sensor at a time when the collection of LEDs is activated, including when the steady-state voltage is programmed between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor.

[0011] In a second embodiment, the electronic device of the first embodiment performs a method, wherein the group of LEDs that is activated is a subset of all LEDs of the display.

[0012] In a third embodiment, the electronic device of the second embodiment performs the method, wherein the activated LED cluster is positioned directly above the under-display sensor.

[0013] Embodiment 4 is a method performed by the electronic device of any one of embodiments 1 to 3, wherein the first programming step is performed during a first frame of the drive circuit, and the second programming step is performed during a second frame of the drive circuit, and the second frame immediately follows the first frame such that the second programming step is the next programming step following the first programming step.

[0014] Embodiment 5 is a method performed by the electronic device of any one of embodiments 1 to 4, wherein activating the LEDs in the LED collection includes: the LEDs emitting a first light intensity that is weaker than the steady-state light intensity by a first deficit intensity in a first emission phase following the first programming phase and preceding the second programming phase; the LEDs emitting a second light intensity that is weaker than the steady-state light intensity by a second deficit intensity that is less in absolute amount than the absolute amount of the first deficit intensity in a second emission phase following the second programming phase and preceding the steady-state programming phase; and the LEDs emitting the steady-state light intensity in a steady-state emission phase following the steady-state programming phase.

[0015] Embodiment 6 is a method performed by the electronic device of embodiment 5, wherein the first light intensity decreases logarithmically in the first emission stage and the second light intensity decreases logarithmically in the second emission stage.

[0016] Embodiment 7 is a method performed by the electronic device of any one of embodiments 5 or 6, wherein the computing device is configured to present video content on the display of the computing device by energizing the LEDs through a dynamic range ranging from low intensity to maximum intensity, the maximum intensity being the same as the steady-state light intensity.

[0017] Embodiment 8 is a method performed by the electronic device of any one of embodiments 5 to 7, including, before activating the collection of LEDs, identifying an initial intensity of the LEDs; determining a difference between the initial intensity and the steady-state light intensity of the LEDs; and determining an amount by which the first overdrive voltage exceeds the steady-state voltage based on the difference between the initial intensity and the steady-state light intensity of the LEDs, wherein the computing device is configured to determine a larger amount for the first overdrive voltage when the difference between the initial intensity and the steady-state light intensity of the LEDs is larger, compared to determining a lower amount for the first overdrive voltage when the difference between the initial intensity and the steady-state light intensity of the LEDs is lower.

[0018] Embodiment 9 is a method performed by the electronic device of any one of embodiments 1 to 8, wherein receiving the instruction to activate the under-display sensor includes receiving an instruction indicating user contact with the display at a user contact position corresponding to the position of the under-display sensor.

[0019] Embodiment 10 is a method performed by the electronic device of any one of embodiments 1 to 9, in which activating the LEDs in the LED collection includes establishing a third overdrive voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor in a third programming stage of the drive circuit that follows the second programming stage and precedes the steady-state programming stage, the third overdrive voltage being a third overvoltage that exceeds the steady-state voltage and is lower than the second overvoltage.

[0020] Embodiment 11 is a method performed by the electronic device of embodiment 10, wherein the reduction from the first overdrive voltage to the second overdrive voltage to the third overdrive voltage and further to the steady-state voltage represents a logarithmic voltage reduction.

[0021] Embodiment 12 is a method performed by the electronic device of any one of embodiments 1 to 11, wherein activating the LEDs in the collection of LEDs includes the drive circuit for the LEDs establishing the steady-state voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor in multiple steady-state programming stages of the drive circuit subsequent to the steady-state programming stage, such that the LEDs emit at a steady-state light intensity over multiple consecutive frames of the display.

[0022] Embodiment 13 is a method performed by the electronic device of any one of Embodiments 1 to 12, in which establishing the first overdrive voltage between the gate terminal of the LED driving transistor and the source terminal of the LED driving transistor comprises a data scan line sending a first data voltage to the drive circuit in the first programming stage, where the first data voltage is lower than a steady-state data voltage; establishing the second overdrive voltage between the gate terminal of the LED driving transistor and the source terminal of the LED driving transistor comprises a data scan line sending a second data voltage to the drive circuit in the second programming stage, where the second data voltage is higher than the first data voltage and lower than the steady-state data voltage; and establishing the steady-state voltage between the gate terminal of the LED driving transistor and the source terminal of the LED driving transistor comprises the data scan line sending the steady-state data voltage to the drive circuit in the steady-state programming stage.

[0023] Embodiment 14 is a method performed by the electronic device of any one of embodiments 1 to 13, wherein the computing device presents video content at a first frame rate on the display, and the computing device establishes the first overdrive voltage and the second overdrive voltage at a second frame rate greater than the first frame rate.

[0024] Embodiment 15 is a method performed by the electronic device of any one of embodiments 1 to 14, wherein the under-display sensor includes an under-display fingerprint sensor.

[0025] Embodiment 16 is directed to a computing device including a display, an under-display sensor positioned below the display, and electronics configured to cause the computing device to perform an operation, the operation including receiving an instruction to activate the under-display sensor positioned below a display of the computing device, and activating a collection of LEDs of the display to provide illumination to the under-display sensor, wherein activating the collection of LEDs includes activating LEDs in the collection of LEDs, wherein a drive circuit of the LEDs establishes a first overdrive voltage, the first overvoltage exceeding a steady-state voltage, between a gate terminal of an LED drive transistor adapted to conduct an LED and a source terminal of the LED drive transistor in a first programming stage of the drive circuit; and in a second programming stage of the drive circuit subsequent to the first programming stage, establishing a second overdrive voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor, the second overdrive voltage being a second overvoltage exceeding the steady-state voltage and being lower than the first overdrive voltage; and in a steady-state programming stage of the drive circuit subsequent to the first programming stage and the second programming stage, the drive circuit for the LEDs starting up the LEDs by establishing the steady-state voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor, the operation further including starting up the under-display sensor by reading a signal from the under-display sensor when the collection of LEDs is started up, including when the steady-state voltage is programmed between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor.

[0026] Embodiment 17 is directed to an electronic apparatus-implemented method, the method including: receiving, at a computing device, an instruction to activate an under-display fingerprint sensor positioned under a display of the computing device; and activating a collection of LEDs of the display to provide illumination to the under-display sensor, wherein activating the collection of LEDs includes activating an LED in the collection of LEDs, wherein a drive circuit of the LED establishes, in a first programming phase of the drive circuit, a first overdrive voltage between a gate terminal of an LED drive transistor adapted to conduct an LED and a source terminal of the LED drive transistor, the first overdrive voltage being a first overvoltage exceeding a steady-state voltage; the LED emits, in a first emission phase following the first programming phase, a first light intensity that is less than a steady-state light intensity by a first under-intensity; and the drive circuit of the LED activates, in a first emission phase of the drive circuit following the first emission phase, a first overdrive voltage exceeding a steady-state light intensity by a first under-intensity. establishing a second overdrive voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor in a second programming phase, the second overdrive voltage being a second overvoltage above the steady-state voltage that is lower than the first overvoltage; the LED emitting a second light intensity that is weaker than the steady-state light intensity by a second under-intensity that is less than the absolute amount of the first under-intensity in a second emission phase subsequent to the second programming phase; the drive circuit of the LED establishing the steady-state voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor in a steady-state programming phase of the drive circuit subsequent to the second emission phase; the LED emitting a steady-state light intensity in a steady-state emission phase subsequent to the steady-state programming phase;and activating the LEDs by establishing the steady-state voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor such that the LEDs emit at a steady-state light intensity over a plurality of consecutive frames of the display, the method further including activating the under-display sensor by reading a signal from the under-display sensor at a time when the collection of LEDs is activated, including when the LEDs emit the steady-state light intensity.

[0027] Embodiment 18 is a method performed by the electronic device of embodiment 17, in which establishing the first overdrive voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor comprises a data scan line sending a first data voltage lower than a steady-state data voltage to the drive circuit in the first programming phase; establishing the second overdrive voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor comprises a data scan line sending a second data voltage higher than the first data voltage and lower than the steady-state data voltage to the drive circuit in the second programming phase; and establishing the steady-state voltage between the gate terminal of the LED drive transistor and the source terminal of the LED drive transistor comprises a data scan line sending the steady-state data voltage to the drive circuit in the steady-state programming phase.

[0028] Embodiment 19 is a method performed by the electronic device of either embodiment 17 or 18, wherein the group of LEDs that is activated is a subset of all LEDs of the display that is located directly above the under-display fingerprint sensor.

[0029] Embodiment 20 is a method performed by the electronic device of any one of embodiments 17 to 19, wherein the first programming step is performed during a first frame of the drive circuit, and the second programming step is performed during a second frame of the drive circuit, and the second frame immediately follows the first frame such that the second programming step is the next programming step following the first programming step.

[0030] Implementations of the above technologies 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 actions described above.

[0031] The details of one or more embodiments of the subject matter herein are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, drawings, and claims. [Brief explanation of the drawings]

[0032] [Figure 1A] FIG. 1 illustrates an exemplary electronic device having a display panel and a fingerprint sensor. [Figure 1B] FIG. 1 illustrates an exemplary electronic device having a display panel and a fingerprint sensor. [Figure 2] FIG. 1C illustrates an exemplary display system of the electronic device of FIGS. 1A and 1B. [Figure 3] 3 is an example block diagram illustrating a timing controller of the example display system of FIG. 2. [Figure 4] FIG. 10 is an example timing diagram of under-display fingerprint sensor operation. [Figure 5] FIG. 2 illustrates an example pixel circuit for a display system. [Figure 6A]FIG. 10 is an exemplary timing diagram illustrating pixel circuit operation without data voltage compensation. [Figure 6B] FIG. 10 is an exemplary timing diagram illustrating pixel circuit operation with data voltage compensation. [Figure 7A] FIG. 10 is an exemplary timing diagram illustrating pixel circuit operation without power supply voltage compensation. [Figure 7B] FIG. 10 is an exemplary timing diagram illustrating pixel circuit operation with power supply voltage compensation. [Figure 8A] 10 is an example graph showing OLED luminance without voltage compensation. [Figure 8B] 10 is an example graph showing OLED luminance with voltage compensation. [Figure 9] 1 is a flow diagram illustrating an example process of brightness control for an under-display fingerprint sensor. DETAILED DESCRIPTION OF THE INVENTION

[0033] Like reference numbers and designations in the various drawings indicate like elements. Detailed Description An example of a flat panel display that can include an under-display fingerprint sensor is an OLED display. An OLED display generally includes an array of pixels, each pixel including one or more OLEDs. An OLED display is typically driven by a driver circuit including a row driver and a column driver. A row driver, e.g., a scan driver, typically sequentially selects each row of pixels in the display, and a column driver, e.g., a data driver, supplies a data voltage to the pixel circuit of the selected row. The pixel circuit generates a current corresponding to the data voltage and supplies the current to the OLED of the pixel, thereby enabling the selected OLED to emit light, thereby displaying an image on the display. Signal lines, such as horizontal scan lines and vertical data lines, can be used to control the pixels to display an image on the display.

[0034] The light intensity of a pixel may be determined by a grayscale value. Pixel light intensity may be represented as a grayscale value, including integers from zero to 255, corresponding to the example of an 8-bit grayscale display. Other grayscale value ranges may also 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 the range from zero to 1, including decimal values ​​therebetween, and the range from zero percent (%) to 100%.

[0035] In a full-color display that spatially combines colors, each pixel can include multiple color channels or subpixels. In some embodiments, each pixel can include each of red, green, and blue subpixels. In some embodiments, each pixel can include each of cyan, magenta, and yellow subpixels. The light intensity of each subpixel can be represented by a grayscale value, as described above, e.g., an integer between zero and 255 for an 8-bit display.

[0036] 1A and 1B are diagrams of an example computing device 100 having a display panel 110 and a fingerprint sensor (FPS) 120. Figure 1A shows a front view of computing device 100. Figure 1B shows an example cross-sectional view of a portion of computing device 100.

[0037] Referring to FIG. 1A , computing device 100 may be, for example, a smartphone, a tablet computer, a television, a smartwatch, or a handheld game console. Display panel 110 includes an array of light-emitting pixels. In operation, display panel 110 can display images by illuminating the light-emitting pixels. Display panel 110 may be, for example, an active matrix organic light-emitting diode (OLED) panel or a light-emitting diode (LED) liquid crystal display (LCD) panel. Computing device 100 includes fingerprint sensor 120 adjacent to display panel 110. For example, fingerprint sensor 120 can be positioned below the display panel, e.g., behind display panel 110 when viewed from a front oblique side of computing device 100.

[0038] 1B, the top layer of a cross section of computing device 100 includes a cover glass 106. Positioned below cover glass 106 is a polarizing film 108. Positioned below polarizing film 108 is a display panel 110 including an array of light-emitting pixels.

[0039] Fingerprint sensor 120 is positioned below display panel 110 in a cross-sectional view of computing device 100. Display panel 110 includes an array of light-emitting pixels. Fingerprint sensor 120 is configured to receive light emitted by at least some of the pixels in the array and reflected from a finger 124 placed on display panel 110 at the location of fingerprint sensor 120. Thus, the pixels of display panel 110 are positioned above fingerprint sensor 120 in some embodiments.

[0040] Fingerprint sensor 120 is mounted relative to display panel 110 such that fingerprint sensor 120 is exposed to light generated by display panel 110 and reflected by finger 124. In some embodiments, fingerprint sensor 120 may be mechanically coupled to the motherboard of computing device 100.

[0041] In some embodiments, fingerprint sensor 120 may be mechanically coupled to an opaque cover positioned below display panel 110, such as back cover 112 of computing device 100. In some embodiments, back cover 112 defines an opening 126. Fingerprint sensor 120 may be aligned with opening 126 to receive light generated by display panel 110 and reflected by finger 124.

[0042] The fingerprint sensor 120 may include a light receiver. In operation, the pixels of the display panel 110 emit light 122. The emitted light 122 reflects off a finger 124 and passes through the display panel 110 to the fingerprint sensor 120. The light receiver of the fingerprint sensor 120 therefore receives a return pulse of reflected light 116.

[0043] The fingerprint sensor 120 may include an optical detector, such as a charge-coupled device (CCD) or a complementary metal-oxide semiconductor circuit (CMOS). The optical detector may include an array of light-sensitive optical sensors. The array of optical sensors may be arranged in rows and columns. A row or column of optical detectors may be considered a line of the FPS.

[0044] A contact detection signal may be generated based on a user interaction with the computing device 100 to trigger operation of the fingerprint sensor 120. For example, a user may place a finger 124 on a portion of the display panel positioned over the fingerprint sensor 120. The display panel 110 may include a sensor, such as a capacitive sensor, that detects contact applied to the display panel 110 by the finger 124. When the capacitive sensor detects contact by the finger 124, the capacitive sensor sends a contact detection signal to the CPU of the computing device 100.

[0045] The CPU can receive a touch detect signal indicating activation of an under-display sensor positioned below the display panel 110. The touch detect signal indicates the presence of a finger 124 on a portion of the display panel positioned above the fingerprint sensor 120. In some embodiments, the fingerprint sensor 120 can have a large area such that a user can touch the display panel 110 at any of multiple locations positioned above the fingerprint sensor 120. In some embodiments, the fingerprint sensor 120 can have a smaller area such that there is a narrow portion of the display panel 110 that the user needs to touch for detection by the fingerprint sensor 120.

[0046] In some embodiments, the contact detection signal may be triggered by a user selection of a virtual user interface element that triggers fingerprint recognition (e.g., a user selection of a "Buy" button, which prompts the computing device to prompt the user to provide a fingerprint and begin analyzing the data received by the fingerprint sensor 120).

[0047] In response to the touch detect signal, the CPU can activate a collection of LEDs on the display to provide illumination to the under-display sensor. The activated collection of LEDs can be a subset of all LEDs on the display. In some embodiments, the activated collection of LEDs is positioned directly above the under-display sensor.

[0048] In operation, each photosensor in fingerprint sensor 120 generates an electrical signal in response to capturing a photon of light. The length of time that a photosensor is exposed to light is called the exposure time or integration time. Each photosensor records a pixel value representing the light incident on the photosensor during the integration time. The pixels form an image of the scanned fingerprint. In some embodiments, an analog-to-digital converter can process the analog electrical signal to generate a digital representation of the fingerprint image.

[0049] The fingerprint image may be compared to stored fingerprint images, e.g., to determine whether the fingerprint is a recognized fingerprint, to determine the user's identity, etc. Based on the recognition of the fingerprint, the computing device may take action. For example, based on recognizing the fingerprint as belonging to an authorized user of the computing device, the computing device may allow the user to access the computing device, complete a purchase using the computing device, etc.

[0050] Fingerprint sensor 120 has an integration time that can be longer than the frame time of the display panel. In some embodiments, fingerprint sensor 120 has an integration time that is much longer than the emission cycle time of the display panel. In one embodiment, the integration time may be approximately 100 milliseconds, the frame time of the display panel may be approximately 16 milliseconds, and the emission cycle time of the display panel may be approximately 4 milliseconds.

[0051] The fingerprint sensor 120 includes multiple sensor lines, e.g., rows, columns, or both. When the fingerprint sensor is activated, the multiple sensor lines are not activated simultaneously. There is a delay between the sensor lines. Thus, the sensor lines have a staggered or rolling shutter and integration start and stop times. As an example, the delay between the start of the integration start time of the first sensor line and the start of the integration time of the last sensor line may be, for example, 50 milliseconds or less, 10 milliseconds or less, 1 millisecond or less, etc.

[0052] FIG. 2 is a diagram of an exemplary display system 200 of computing device 100. Display system 200 is an OLED display system including an array 212 of light-emitting pixels. Each light-emitting pixel includes an OLED. The OLED display is driven by a driver including a SCAN / EM driver 208 and a data driver 210. SCAN / EM driver 208 can be an integrated, or stacked, row line driver. Generally, SCAN / EM driver 208 selects a row of pixels in the display, and data driver 210 provides data signals (e.g., voltage data (VDATA)) to the pixels in the selected row to light up the selected OLEDs according to image data. Signal lines such as scan lines, EM lines, and data lines can be used in controlling the pixels to display an image on the display. While FIG. 2 shows display system 200 with SCAN / EM driver 208 on one side, SCAN / EM driver 208 can be located on both the left and right sides of the display, thereby improving driving performance (e.g., speed).

[0053] The display system 200 includes a pixel array 212 that includes a plurality of light-emitting pixels, e.g., pixels P11 through P43. Pixels are microscopic elements on a display that can change color based on image data supplied to them. Each pixel in the pixel array 212 can be separately addressed to produce various intensities of color. Each pixel maintains a largely stable luminance over a frame time, displaying light corresponding to the supplied image data as programmed. The frame time, or frame period, is the length of time between the start of one frame and the start of the next. The frame time can be the reciprocal of the frame rate of the display system. For example, a frame rate of 60 frames per second (fps) corresponds to a frame time of 1 / 60th of a second, or 0.0167 seconds.

[0054] The pixel array 212 extends in a plane and includes rows and columns. Each row extends horizontally across the pixel array 212. For example, the first row 220 of the pixel array 212 includes pixels P11, P12, and P13. Each column extends vertically downward across the pixel array 212. For example, the first column 230 of the pixel array 212 includes pixels P11, P21, P31, and P41. For simplicity, only a few pixels are shown in FIG. 2 . In reality, the pixel array 212 may have thousands or millions of pixels. The more pixels there are, the higher the image resolution.

[0055] The display system 200 includes a display driver integrated circuit (DDIC) 206 that receives display input data 202. The DDIC may be, for example, a semiconductor integrated circuit or a state machine. The DDIC generates the appropriate voltage, current, timing, and demultiplexing signals to display an image on the display 110 according to the display input data 202. In some embodiments, the DDIC may be a microcontroller and may incorporate RAM, flash memory, EEPROM, ROM, etc.

[0056] The DDIC 206 includes a timing controller 234, a clock signal generator 236, and a data signal generator 238. The DDIC 206 generates a clock signal 242. The clock signal 242 may be, for example, a signal that controls a display frame start time and a display frame stop time for each frame presented by the display panel 110. In some embodiments, the clock signal 242 may be a signal that controls a display light start time and a display light stop time for each emission cycle of the display panel 110.

[0057] Display system 200 includes a SCAN / EM driver 208 and a data driver 210. In some embodiments, SCAN / EM driver 208, data driver 210, or both may be integrated with DDIC 206. The SCAN / EM driver provides SCAN signals and EM signals to rows of pixel array 212. For example, SCAN / EM driver 208 provides scan signals via scan lines S1-S4 and EM signals via EM lines E1-E4 to the rows of pixels.

[0058] The data driver 210 provides signals to columns of the pixel array 212. For example, based on an image data signal 244 from the DDIC 206, the data driver 210 provides data to the columns of pixels via data lines D1-D4. The data driver 210 selects a data voltage for each pixel according to the image data signal 244. The data driver 210 provides the selected data voltage as a data signal to the data lines D1-D4.

[0059] The clock signal 242 can be used to drive the SCAN / EM driver 208 and the data driver 210. Thus, the DDIC 206 controls the timing of the scan, EM, and data signals.

[0060] The display system 200 includes a power supply 250. The power supply 250 provides a first power supply voltage ELVDD and a second power supply voltage ELVSS. In some embodiments, the power supply 250 can be integrated with the DDIC 206.

[0061] Each pixel in pixel array 212 is addressable by horizontal scan and EM lines and vertical data lines. For example, pixel P11 is addressable by scan line S1, EM line E1, and data line D1. In another example, pixel P32 is addressable by scan line S3, EM line E3, and data line D2.

[0062] The SCAN / EM driver 208 and the data driver 210 provide signals to the pixels, enabling the pixels to reproduce images on the display. The SCAN / EM driver 208 and the data driver 210 provide signals to the pixels via scan lines, emission lines, and data lines. To provide signals to the pixels, the SCAN / EM driver 208 selects a scan line and controls the light-emitting operation of the pixel. The data driver 210 provides data signals to the pixels addressable by the selected scan line to cause the selected OLED to emit light according to image data.

[0063] The scan lines are addressed sequentially, frame by frame. A frame is a single image in a series of images being displayed. The scan direction determines the order in which the scan lines are addressed. In display system 200, the scan direction is from the top to the bottom of pixel array 212. For example, scan line S1 is addressed first, then scan line 2, then S3, and so on.

[0064] The DDIC 206 can communicate with the fingerprint sensor controller 240, for example, via an electrical connection. In some embodiments, the DDIC 206 can include the fingerprint sensor controller 240. The fingerprint sensor controller 240 controls the operation of the fingerprint sensor 120. In some embodiments, the fingerprint sensor controller 240 can receive a contact detect signal from the computing device and communicate with the DDIC to indicate that the FPS should be activated. In some embodiments, the DDIC can receive a contact detect signal from the computing device and communicate with the fingerprint sensor controller 240 to indicate that the FPS should be activated.

[0065] 2 shows example components of an OLED display, the techniques described are applicable to any flat panel display that includes an array of pixels. For example, the process for reducing artifacts due to electromagnetic radiation can be applied to light emitting diodes (LEDs), liquid crystal displays (LCDs), and plasma display panels (PDPs).

[0066] 3 is an example block diagram of the timing controller 234 of the DDIC 206. The timing controller includes a mobile industry processor interface (MIPI) receiver 302, a frame memory 304, a register bank 306, and a command parser 308. The timing controller 234 includes an under display fingerprint sensor (UDFPS) lighting overlay 310 and a compensation generator 312.

[0067] When a finger touch is detected at the UDFPS location, a local high brightness mode (LHBM) 314 is activated for the portion of the display panel overlying the UDFPS. A compensation generator 312 generates a compensated voltage. In some embodiments, the compensation generator 312 generates a compensated VDATA signal 320 for the UDFPS illumination overlay. The compensated VDATA signal 320 overdrives the VDATA of affected pixels of the display panel to increase the speed at which the pixels reach high brightness. In some embodiments, the compensation generator 312 generates a compensated ELVDD signal 324. The compensation generator 312 can output the compensated ELVDD signal 324 to a power supply 350. The compensated ELVDD signal 316 overdrives the ELVDD of affected pixels of the display panel to increase the speed at which the pixels reach high brightness. The effects of the compensated VDATA signal 320 and the compensated ELVDD signal 316 are described in more detail with reference to FIGS. 6 and 7, respectively.

[0068] 4 is an example timing diagram 400 of under-display fingerprint sensor operation. Timing diagram 400 includes stages including contact detection 401, display on and pattern generation 407, LHBM 411, stabilization (“stable”) 413, sensor integration 415, and image generation 417. In timing diagram 400, the frame time can be, for example, 16.6 ms or 33.2 ms.

[0069] In touch detection 401, the display panel can be turned on or off. The contact IC can be in a low-power or idle mode 402 until a touch is detected. The contact IC undergoes debounce 404 for approximately three frames. Debounce can be used to ensure that time-consuming tasks such as fingerprint detection do not trigger too frequently. Debounce delays activation of the contact IC. The contact IC undergoes scan and process 406 to measure the location where the touch is detected and generate a touch detect signal. The contact IC sends the touch detect signal to the CPU of the computing device 100.

[0070] In display on and pattern generation 407, the CPU powers up the display with a power-up sequence 408. The length of time for the power-up sequence 408 may depend on the state of the display panel before the detected touch. For example, if the display panel is on, the power-up sequence 408 may be shorter or unnecessary. The CPU initiates pattern generation 410 to draw a pattern representing the location of the detected touch. The FPS can then perform fingerprint detection at the location of the detected touch.

[0071] In some embodiments, the CPU can draw a pattern on the display panel to indicate to the user where the UDFPS is located. For example, a user may open an application that requires fingerprint detection to access the application. The CPU can draw a pattern on the display panel to mark where the user places their finger.

[0072] In LHBM 411, the pixel at the sensing location is triggered to enter a localized high brightness mode. LHBM 411 may have a duration of approximately one frame. In stabilization 413, the pixel ramps up from a previous brightness level to a high brightness and remains stable at the high brightness. Stabilization 413 may have a duration of approximately three frames. Implementations of the present disclosure can be used to shorten the duration of stabilization phase 413.

[0073] Once stabilization has occurred, the CPU activates the under-display sensor by reading the signal from the under-display sensor. Thus, once the pixels have stabilized at high brightness, sensor integration 415 begins. During sensor integration 415, the sensor sites of the fingerprint sensor capture photons. Sensor integration 415 can have a duration of approximately 100 milliseconds.

[0074] Once the sensor integration 415 is complete, the fingerprint sensor transfers data 418 to the CPU. For example, the fingerprint sensor may transfer data 418 representing an image of the fingerprint.

[0075] During image generation 417, the CPU uses the fingerprint to perform authentication 420. Based on authentication 420, the CPU renders an image 422 on the display panel. For example, based on fingerprint authentication, the CPU can determine that the user is authorized to view a particular display screen and can render an image of that particular display screen. The display then returns to normal operation 424.

[0076] FIG. 5 is a diagram 500 of an LED and corresponding drive circuitry of a display system (diagram 500 can also represent a sub-pixel LED and corresponding drive circuitry, but for simplicity, may hereinafter be referred to as pixel 500). For example, FIG. 5 may show a more detailed diagram of a pixel of display system 200. Pixel 500 is an active matrix OLED (AMOLED) pixel. Pixel 500 receives a scan signal "SCAN(N)" and a reset scan signal "SCAN(N-1)." Pixel 500 receives a data voltage "VDATA" and an emission signal "EM." Pixel 500 receives a first power supply voltage ELVDD and an initial reference voltage VINIT. Pixel 500 is connected to a common ground ELVSS.

[0077] The pixel 500 includes an organic light-emitting diode (OLED) 520. The OLED 520 includes a layer of organic compounds that emits light in response to a current IOLED. The organic layer is disposed between two electrodes, an anode and a cathode. The OLED 520 is driven by a current source circuit that receives a power supply voltage ELVDD. The current source circuit drives the OLED 520 to emit light.

[0078] The pixel 500 includes a storage capacitor CST 506, transistors T2-T7, and an OLED drive transistor 508. The pixel 500 is programmed by control signals, namely, SCAN, EM, and VDATA. The OLED current IOLED varies based on the voltage present across the LED drive transistor 508. The drive transistor 508 has a gate terminal (G), a source terminal (S), and a drain terminal (D). The drive transistor 508 has a threshold voltage VTH. The threshold voltage VTH is the minimum gate-to-source voltage required to form a conductive path between the source and drain terminals of the drive transistor 508.

[0079] In operation, pixel 500 goes through an initialization phase, a programming phase, and an emission phase. During the initialization phase, OLED 520 is turned off in preparation for programming. OLED 520 is turned off by switching off the EM signal (by setting it high), thereby turning off T5 and T6. The SCAN(N-1) signal is turned on, thereby turning on T4 and setting G to VINIT.

[0080] During the programming phase, the SCAN(N) signal is turned on, thereby turning on T2, T3, and T7. Voltage data VDATA passes through T2 to drive transistor 508, thereby setting G to VDATA minus VTH. Thus, when pixel 500 receives data voltage VDATA during the programming phase of a frame, this voltage is programmed onto the “G” node of drive transistor 508.

[0081] During the emission phase, the EM(N) signal is turned on, thereby turning on T5 and T6. A current flows through the OLED 520, with the current level of the OLED 520 being determined by G. Thus, after the pixel 500 transitions to the emission phase of a frame, a current IOLED flows through the OLED 520 based on a voltage set at the "G" node of the drive transistor (e.g., based on the received data voltage VDATA) so that the OLED 520 emits light when the current IOLED flows through it. The intensity or brightness of the light depends on the amount of applied current IOLED. A higher current generally results in brighter light. Thus, the intensity of the light emitted from the OLED 520 is based on VDATA, which is programmed into the "G" node and corresponds to the image data for the individual pixel. A storage capacitor CST maintains this pixel state so that the pixel 500 remains illuminated throughout the emission phase following the programming / addressing phase.

[0082] FIG. 6A shows an example timing diagram of pixel circuit operation without data voltage (VDATA) compensation. The voltages shown in FIGS. 6A and 6B are referenced to ground. As shown in FIG. 6A, when the pixel switches to high brightness, VDATA changes 602 from a higher value to a lower value. The higher value corresponds to the initial color of the pixel before activating the high brightness mode. In some embodiments, the higher value can correspond to a black pixel color, and the lower value can correspond to a white pixel color. In some embodiments, the higher value can correspond to a grayscale pixel color.

[0083] Although described as black, grayscale, or white, the diagrams shown in Figures 6A and 6B can represent the behavior of sub-pixels of a pixel. Thus, in some embodiments, higher and lower values ​​of VDATA can correspond to darker and lighter intensities of the sub-pixel color.

[0084] The pixel enters an initialization phase 601 by receiving a reset signal SCAN(N-1). In the initialization phase 601, the gate voltage G is dropped 611 from a first value 623 to a lower value, e.g., VINIT. The pixel then enters a first programming phase 621 by receiving a scan signal SCAN(N). In some embodiments, the first programming phase 621 occurs during the first frame of the drive circuit.

[0085] In a first programming phase 621, a change in VDATA causes the gate voltage G to increase from VINIT to a second voltage 603. The second voltage 603 is higher than VINIT but lower than the first value 623. The change in VDATA also changes VTH over time 622. In a subsequent second programming phase 631, the gate voltage G changes from the second value 603 to a third value 604. In a subsequent second programming phase 641, the gate voltage G changes again from the third value 604 to a fourth value 605. After a fourth programming phase 651, the gate voltage G reaches a steady-state value 640.

[0086] A change in gate voltage G from a first value 623 to a second value 603 causes IOLED to rise 606 and then decay 607. After the first programming phase 621 and before the second programming phase 631, the OLED is illuminated and emits light during a first emission phase. The decay 607 during the emission phase occurs by changing VTH during the emission phase due to changes in the electrical characteristics of the drive transistor 508 as current flows from source to drain during emission. Each programming phase 631, 641 causes a change in gate voltage G, for example, to values ​​604 and 605, respectively. IOLED rises with each emission phase and is initially limited in magnitude due to the capacitance of the OLED. The OLED current during each emission phase decays due to changes in the threshold voltage of the drive transistor 508 during each emission phase. After a fourth programming phase 651, VTH reaches a steady-state value 633, gate voltage G reaches a steady-state value 640, and IOLED reaches a steady-state current 610.

[0087] As can be seen in Figure 6A, it takes multiple programming steps of the pixel before the OLED reaches a steady-state current 610. Thus, the brightness or luminance of the pixel gradually increases during this time. Although shown as occurring over four programming steps, the rise of IOLED to steady state can occur over more or fewer programming steps, for example, two, three, five, or six programming steps.

[0088] Figure 8A shows an example graph 810 illustrating IOLED, or pixel luminance, over time for a pixel operated according to Figure 6A. Each oscillation in graph 810 represents an emission cycle of IOLED. The solid line graph 801 in Figure 8A represents the expected or ideal pixel luminance as a result of a change in VDATA from dark to light. As shown in Figure 8A, IOLED gradually rises to a steady-state value.

[0089] 6B shows an example timing diagram of pixel circuit operation with VDATA compensation. Generally, data voltage compensation is applied by sending reduced VDATA signals 613, 614, 615 to the pixel circuit to cause a more rapid voltage change in the gate voltage G of the drive transistor 508 compared to the voltage change shown in FIG. 6A without data voltage compensation. The more rapid change in the gate voltage G causes a more rapid increase in the current (IOLED) through the OLED 520. Therefore, the OLED 520 reaches high brightness more quickly with the applied VDATA compensation.

[0090] 6B, similar to FIG. 6A, when a pixel switches to high brightness, VDATA changes 602 from initial VDATA 628 to a new steady-state VDATA 630. Initial VDATA 628 is higher than steady-state VDATA 630. The difference between initial VDATA 628 and steady-state VDATA 630 represents the brightness change between the initial pixel brightness and the new brighter pixel brightness. For example, for a change from black to white, the difference between initial VDATA 628 and steady-state VDATA 630 will be larger than for a change from gray to white.

[0091] The pixel enters the programming phase 661 by receiving a scan signal SCAN(N). In the first programming phase 661, a first reduced VDATA signal 613 is applied. The first reduced VDATA signal 613 is reduced compared to the steady state VDATA 630. This reduction in VDATA compared to the steady state VDATA 630 establishes a higher voltage at the “G” node of the drive transistor 508 than would be the case if VDATA 630 were applied to the “G” node of the drive transistor 508. At the end of the first programming phase 661, the gate voltage G is the difference between the reduced VDATA signal 613 and the current magnitude of VTH.

[0092] In some embodiments, the difference between the first reduced VDATA signal 613 and the steady-state VDATA 630 is determined based on the difference between the initial VDATA 628 and the steady-state VDATA 630. For example, if the difference between the initial VDATA 628 and the steady-state VDATA 630 is smaller, the difference between the reduced VDATA signal 613 and the steady-state VDATA 630 may be smaller. Conversely, if the difference between the initial VDATA 628 and the steady-state VDATA 630 is larger, the difference between the first reduced VDATA signal 613 and the steady-state VDATA 630 may be larger. In one embodiment, the initial VDATA 628 may be 5 volts, which corresponds to black, and the steady-state VDATA 630 may be 1 volt, which corresponds to white. The first reduced VDATA signal 613 may be minus 1 volt.

[0093] The first reduced VDATA signal 613 establishes an overdrive voltage between the gate and source terminals of transistor 508. The overdrive voltage can be expressed as the difference between the gate voltage "G" and the source voltage "S" of drive transistor 508. The overdrive voltage is the excess voltage compared to the steady-state voltage between the gate and source terminals.

[0094] In a first programming phase, the gate voltage G changes from a first value 623 to a second value 644 due to a change in VDATA. The second value 644 in FIG. 6B is less than the second value 603 in FIG. 6A due to the first reduced VDATA signal 613 that occurs in programming phase 661. Thus, the change in gate voltage G between the first value 623 and the second value 644 in FIG. 6B is greater than the change in gate voltage G between the first value 623 and the second value 603 in FIG. 6A.

[0095] As a result of the change in gate voltage G, IOLED increases 616. The increase 616 in FIG. 6B is greater than the increase 606 in FIG. 6A. A graph of IOLED from FIG. 6A is shown by dashed line 650 in FIG. 6B for comparison. After the first programming stage 621 and before the second programming stage 631, in a first emission stage, the OLED is illuminated and emits light at a first light intensity. The first light intensity is weaker than the steady-state light intensity corresponding to IOLED 620 by a first deficit intensity (although, in ideal compensation, the first light intensity would be the same as the steady-state light intensity). In some embodiments, the first light intensity decreases logarithmically in the first emission stage, for example, according to decay 617.

[0096] A second reduced VDATA signal 614 is then applied in a second programming phase 671. In some embodiments, the second programming phase 671 occurs during a second frame of the driver circuit. In some embodiments, the second frame immediately follows the first frame. The second reduced VDATA signal 614 is reduced by a smaller amount than the first reduced VDATA signal 613 so that the value of the second reduced VDATA signal 614 is closer to the steady-state VDATA 630 than the first reduced VDATA signal 613. Thus, the voltage of the second reduced VDATA signal 614 is higher than the voltage of the first reduced VDATA signal 614 and lower than the steady-state VDATA signal 630. In some embodiments, the difference in magnitude between the first reduced VDATA signal 613, the second reduced VDATA signal 614, and subsequent reduced VDATA signals exhibits an exponential decay. In the above example, the first reduced VDATA signal 613 may be minus 1 volt, and the second reduced VDATA signal 614 may be minus 0.5 volts.

[0097] The second reduced VDATA signal 614 establishes a second overdrive voltage between the gate and source terminals of transistor 508. The second overdrive voltage can be expressed as the difference between VTH and G. The second overdrive voltage is an excess voltage compared to the steady-state voltage between the gate and source terminals. The second overdrive voltage is less than the first overdrive voltage.

[0098] After the second programming stage 671 and before the third programming stage 681, in a second emission stage, the OLED is illuminated and emits light at a second light intensity. The second light intensity is less than the steady-state light intensity corresponding to the IOLED 620 by a second deficit intensity. The absolute amount of the second deficit intensity is less than the absolute amount of the first deficit intensity. In some embodiments, the second light intensity decreases logarithmically during the second emission stage.

[0099] After the programming phase 671, the gate voltage G is the difference between the second reduced VDATA signal 614 and the current magnitude of VTH. Similarly, after the programming phase 681, the gate voltage G is the difference between the third reduced VDATA signal 615 and the current magnitude of VTH. Due to the change in VTH 643 offsetting the difference between the second reduced VDATA signal 614 and the third reduced VDATA signal 615, the gate voltage G maintains the second value 644 after both the second programming phase 671 and the third programming phase 681. The final, steady-state value of the gate voltage G is the difference between the steady-state VDATA 630 and the steady-state VTH 653.

[0100] In a third programming phase 681, a third reduced VDATA signal 615 establishes a third overdrive voltage between the gate and source terminals of transistor 508. The third overdrive voltage is an excess voltage compared to the steady-state voltage between the gate and source terminals. The third overdrive voltage is less than the first overdrive voltage and less than the second overdrive voltage. In some embodiments, the third programming phase 681 occurs during a third frame of the drive circuit. In the above example, the first reduced VDATA signal 613 can be minus 1 volt, the second reduced VDATA signal 614 can be minus 0.5 volts, and the third reduced VDATA signal 615 can be minus 0.2 volts.

[0101] After the third programming stage 681 and before the fourth programming stage 691, in a third emission stage, the OLED is illuminated and emits light at a third light intensity. The third light intensity is less than the steady-state light intensity corresponding to the IOLED 620 by a third deficit intensity. The absolute amount of the third deficit intensity is less than the absolute amounts of the first and second deficit intensities. In some embodiments, the third light intensity decreases logarithmically during the third emission stage.

[0102] A change in gate voltage G from a first value 623 to a second value 644 causes IOLED to rise 616 and then decay 617. Each programming step 671, 681 causes a corresponding rise 618, 619 in IOLED, each followed by a decay. In a fourth, steady-state programming step 691, the drive circuit establishes a steady-state voltage between the gate and source terminals of drive transistor 508 by setting VDATA to steady-state VDATA 630. In a fourth emission step following steady-state programming step 691, the OLED is illuminated and emits light at a steady-state light intensity corresponding to IOLED 620. In some embodiments, the steady-state light intensity is the maximum intensity value of the OLED's dynamic range during normal operation (e.g., during the display of visual content excluding its role as a light source for an under-display sensor).

[0103] In some embodiments, the reduction from the first overdrive voltage to the second overdrive voltage to the third overdrive voltage to the steady-state voltage exhibits a logarithmic voltage reduction. In some embodiments, the display panel presents video content through the display at a first frame rate, and the overdrive voltages are established at a second frame rate different from the first frame rate. For example, the first overdrive voltage, the second overdrive voltage, and the third overdrive voltage can each be established at a second frame rate greater than the first frame rate.

[0104] After steady state programming step 691, V reaches a steady state value 653, gate voltage G remains at second value 644, and I reaches steady state IOLED 620. In some embodiments, in multiple steady state programming steps after steady state programming step 691, the drive circuit establishes a steady state voltage between the gate and source terminals of transistor 508. Thus, OLED emits at a steady state intensity over multiple consecutive frames of the display.

[0105] As can be seen in Figure 6B, the change in VDATA 602 causes a rise in IOLED over several programming steps of the pixel before OLED reaches a steady-state IOLED 620. Thus, the brightness, intensity, and luminance of the pixel gradually increase during this time. However, the rises 616, 618, and 619 are greater than the corresponding rises 606, 608, and 609 in Figure 6A, respectively. Thus, the pixel reaches full brightness more quickly in Figure 6B compared to Figure 6A due to the compensated VDATA.

[0106] FIG. 8B shows an example graph 820 illustrating pixel luminance over time for a pixel operated according to FIG. 6B. Each oscillation in graph 820 represents an EM pulse for the pixel. The solid line graph 801 in FIG. 8B represents the expected or ideal pixel luminance as a result of a change in VDATA from dark to light. As shown in FIG. 8B, IOLED rises quickly to its steady-state value. Thus, the rise in pixel luminance in FIG. 8B occurs more rapidly compared to the rise in pixel luminance in FIG. 8A. Referring back to FIG. 4, the more rapid rise in pixel luminance results in a shorter period for stabilization 413.

[0107] After a steady-state voltage is established between the gate and source terminals of transistor 508 for each LED in the collection of LEDs (the operation of a single such LED in a collection is described above), the DDIC 206 can activate the under-display sensor, for example, by sending a control signal to fingerprint sensor controller 240. Fingerprint sensor controller 240 can then begin sensor integration 415 of fingerprint sensor 120.

[0108] An example timing diagram of pixel circuit operation without power supply voltage (ELVDD) compensation is shown in Figure 7A. The operation of the pixel shown in Figure 7A is the same as that of the pixel shown in Figure 6A. As shown in Figure 7A, ELVDD maintains a constant steady-state value 701 throughout pixel operation.

[0109] Figure 8A shows an example graph 810 illustrating IOLED, or pixel luminance, over time for a pixel operated according to Figure 7A. Each oscillation in graph 810 represents an emission cycle of IOLED. The solid line graph 801 in Figure 8A represents the expected or ideal pixel luminance as a result of a change in VDATA from dark to light. As shown in Figure 8A, IOLED gradually rises to a steady-state value.

[0110] 7B shows an example timing diagram of pixel circuit operation with power supply voltage (ELVDD) compensation. Generally, ELVDD compensation is applied by sending elevated ELVDD signals 702, 704, 706 to the pixel circuit to cause a more rapid rise in current (I OLED ) through the OLED 520 compared to the current rise shown in FIG. 7A. Thus, the OLED 520 reaches high brightness more quickly with the application of ELVDD compensation.

[0111] ELVDD compensation can be added by supplying a first ELVDD 702 at a voltage higher than the steady-state ELVDD 701, and then supplying a second ELVDD 704 at a voltage higher than the steady-state ELVDD 701 but lower than the first ELVDD 702. A third ELVDD 706 can be applied at a voltage higher than the steady-state ELVDD 701 but lower than both the first ELVDD 702 and the second ELVDD 704. The ELVDD can then return to the steady-state ELVDD 701.

[0112] In some embodiments, the first ELVDD 702 is applied as VDATA changes 716 to produce high brightness for the fingerprint sensor. Between the first programming stage 711 and the second programming stage 721, a change from the first ELVDD 702 to the second ELVDD 704 can occur. Between the second programming stage 721 and the third programming stage 731, a change from the second ELVDD 704 to the third ELVDD 706 can occur. Between the third programming stage 731 and the fourth, steady-state programming stage 741, a change from the third ELVDD 706 to the steady-state ELVDD 701 can occur.

[0113] In some cases, all pixels of a display panel are supplied with the same ELVDD. Therefore, when ELVDD compensation is applied, pixels of the display outside the area above the fingerprint sensor are also affected by the changed ELVDD. To avoid interfering with the light intensity of pixels outside the fingerprint sensor area, the VDATA of those pixels can be adjusted based on the ELVDD.

[0114] For example, when a first ELVDD 702 is applied, VDATA can be set to a first VDATA 722, which is higher than the steady-state VDATA 742. Then, while ELVDD varies from the first ELVDD 702 to the fourth ELVDD 701, VDATA can be stepped down, for example, to VDATA 722, VDATA 732, and VDATA 742. Adjusting VDATA can reduce undesirable effects that the varying ELVDD has on the luminance of pixels not located over the fingerprint sensor.

[0115] FIG. 8B shows an example graph 820 illustrating pixel luminance over time for a pixel operated according to FIG. 7B. Each oscillation in graph 820 represents an EM pulse for the pixel. The solid line graph 801 in FIG. 8B represents the expected or ideal pixel luminance as a result of a change in VDATA from dark to light. As shown in FIG. 8B, IOLED rises rapidly to its steady-state value. Thus, the rise in pixel luminance in FIG. 8B occurs more rapidly compared to the rise in pixel luminance in FIG. 8A. Referring back to FIG. 4, the more rapid rise in pixel luminance results in a shorter period for stabilization 413. The shortened period for stabilization 413 can shorten the period from when touch is detected 401 to when authentication 420 and image drawing 422 are completed.

[0116] 9 is a flow diagram illustrating an example process 900 of brightness control for an under-display fingerprint sensor. Process 900 includes receiving an instruction to activate an under-display sensor positioned below a display of a computing device (902). For example, referring to FIG. 4, a contact IC detects contact of a finger 124 with the display panel 110 and generates a contact detection signal. In some embodiments, an application program causes the computing device to prompt a user to place a finger on the under-display sensor and also generates an instruction to activate the under-display sensor.

[0117] The process 900 includes establishing 904 a first overdrive voltage for an LED drive transistor adapted to energize an LED of a display. For example, referring to FIGS. 3 and 6B, the compensation generator 312 generates a compensated VDATA signal 320. Based on the VDATA signal 320, the DDIC 206 provides a first reduced VDATA signal 613 to pixels located in the UDFPS region to establish a first overdrive voltage between the gate and source of each LED drive transistor of the pixel LED.

[0118] The process 900 includes establishing 906 a second overdrive voltage for an LED drive transistor that is less than the first overdrive voltage. For example, referring to FIG. 6B, the DDIC 206 provides a second reduced VDATA signal 614 to a pixel located in the UDFPS region to establish the second overdrive voltage for the LED drive transistor of the pixel LED.

[0119] The process 900 includes establishing 908 a steady-state voltage for an LED drive transistor that is less than the first overdrive voltage and the second overdrive voltage. For example, referring to FIG. 6B, to establish a steady-state voltage for an LED drive transistor of a pixel LED, the DDIC 206 sets VDATA to the steady-state VDATA 630 for a pixel located in the UDFPS region.

[0120] The process 900 includes activating 910 an under-display sensor. For example, referring to FIG. 2, once the collection of LEDs located above the fingerprint sensor 120 are activated and stabilized, the DDIC 206 sends a signal to the fingerprint sensor controller 240 to activate the fingerprint sensor 120.

[0121] Embodiments of the subject matter and functional operations described herein may be implemented in any suitable electronic device, such as a personal computer, a mobile phone, a smartphone, a smart watch, a smart TV, a portable audio or video player, a game console, or a combination of one or more of these devices.

[0122] The electronic device may include various components such as a memory, a processor, a display, and an input / output unit. The input / output unit may include, for example, a transceiver capable of communicating with one or more networks to transmit and receive data. The display may be any suitable display for displaying images, including, for example, a cathode ray tube (CRT), a liquid crystal display (LCD), or a light emitting diode (LED) display.

[0123] Various implementations of the systems and techniques described herein can be realized in digital electronic circuitry, integrated circuits, 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, whether special purpose or general purpose, executable and / or interpretable on a programmable system including at least one programmable processor, which can be coupled to receive data and instructions from, and transmit data and instructions to, a storage system, at least one input device, and at least one output device.

[0124] Embodiments may be implemented as one or more computer program products, e.g., one or more modules of computer program instructions encoded on a computer-readable medium for execution by or to control the operation of a data processing apparatus. The computer-readable medium may be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter producing a machine-readable propagated signal, or a combination of one or more of these. The term "data processing apparatus" encompasses all apparatuses, devices, and machines for processing data, including, by way of example, a programmable processor, a computer, or a multiprocessor or computer. In addition to hardware, an apparatus may include code that forms an execution environment for a subject computer program, such as code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of these. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that encodes information for transmission to an appropriate receiver apparatus.

[0125] A computer program (also referred to as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as modules, components, subroutines, or other units suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored as part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the subject program, or in multiple linked files (e.g., one or more modules, subprograms, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communications network.

[0126] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both.

[0127] Elements of a computer may include a processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include one or more mass storage devices, such as magnetic, magneto-optical, or optical disks, for storing data, or be operatively coupled to receive data from and / or transmit data to such devices. However, a computer need not have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, by way of example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices, magnetic disks, such as internal hard disks or removable disks, magneto-optical disks, and CD-ROM and DVD-ROM disks. The processor and memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[0128] While many specific implementation details are described herein, these should not be construed as limitations on the scope of what can be claimed, but rather as descriptions of features that may be unique to particular embodiments. Certain features that are described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable combination. Also, while features may be described above as functioning in a combination and initially claimed as such, one or more features of a claimed combination may, in some cases, be excluded from that combination, and the claimed combination may include subcombinations or variations of subcombinations.

[0129] Similarly, although the figures may depict operations in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown, or in a sequential order, or that all of the depicted operations be performed, to achieve desirable results. In some situations, multitasking and parallel processing may be advantageous. Also, the separation of various system modules and components in the above-described embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may be integrated together as a single software product or packaged into multiple software products.

[0130] The foregoing describes specific embodiments of the present subject matter. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. By way of example, the processes depicted in the accompanying figures do not necessarily require the particular order or sequential order shown to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.

Claims

1. A method implemented by an electronic device, comprising: receiving, at a computing device, instructions to activate an under-display sensor positioned below a display of the computing device; activating a collection of LEDs in the display to provide illumination to the under-display sensor; activating the LED collection includes activating LEDs in the LED collection, a data line of the display providing a first overdrive voltage to the driving circuit of the LED during a first programming phase of the driving circuit of the LED, the first overvoltage exceeding a steady-state voltage; the data lines of the display supplying a second overdrive voltage to the driver circuit of the LED in a second programming stage of the driver circuit following the first programming stage, the second overdrive voltage being a second overvoltage above the steady-state voltage that is lower than the first overvoltage; the data lines of the display supplying the steady-state voltage to the driver circuits of the LEDs in a steady-state programming phase of the driver circuits subsequent to the first programming phase and the second programming phase; activating the LED by The method comprises: The method performed by the electronic device further includes activating the under-display sensor by reading a signal from the under-display sensor when the group of LEDs is activated based on providing the steady-state voltage to the drive circuit of the LED.

2. 10. The electronic device-implemented method of claim 1, wherein the collection of LEDs that are activated is a subset of all LEDs of the display.

3. 3. The electronic device-implemented method of claim 2, wherein the group of LEDs that are activated are positioned directly above the under-display sensor.

4. the first programming step occurs during a first frame of the drive circuit; the second programming step occurs during a second frame of the drive circuit; 4. The method performed by an electronic device according to claim 1, wherein the second frame immediately follows the first frame such that the second programming stage is the immediately next programming stage following the first programming stage.

5. activating the LEDs in the collection of LEDs includes: the LED emitting a first light intensity that is less than a steady-state light intensity by a first deficit intensity in a first emission phase following the first programming phase and prior to the second programming phase; the LED emitting a second light intensity that is weaker than the steady-state light intensity by a second deficit intensity that is less in absolute amount than the first deficit intensity in a second emission phase that follows the second programming phase and precedes the steady-state programming phase; The method performed by the electronic device of any one of claims 1 to 4, further comprising: the LED emitting the steady-state light intensity in a steady-state emission phase subsequent to the steady-state programming phase.

6. 6. The method performed by the electronic device of claim 5, wherein the first light intensity decreases logarithmically during the first emission stage and the second light intensity decreases logarithmically during the second emission stage.

7. the computing device is configured to present video content on the display of the computing device by energizing the LEDs through a dynamic range ranging from low intensity to maximum intensity; 7. The method performed by an electronic device according to claim 5 or 6, wherein the maximum intensity is the same as the steady-state light intensity.

8. The LEDs have an initial light intensity before activating the LED cluster, and the method comprises: identifying the initial light intensity of the LEDs before activating the LED collection; determining a difference between the initial light intensity and the steady-state light intensity of the LED; and determining an amount by which the first overdrive voltage exceeds the steady-state voltage based on the difference between the initial light intensity and the steady-state light intensity of the LED, wherein the computing device is configured to determine a larger amount for the first overdrive voltage when a difference between the initial light intensity and the steady-state light intensity of the LED is larger, compared to determining a lower amount for the first overdrive voltage when the difference between the initial light intensity and the steady-state light intensity of the LED is lower.

9. A method executed by an electronic device described in any one of claims 1 to 8, wherein receiving the instruction to activate the under-display sensor includes receiving an instruction indicating user contact with the display at a user contact location corresponding to the location of the under-display sensor.

10. activating the LEDs in the collection of LEDs includes:

10. The method executed by the electronic device of claim 1, wherein the data lines of the display include supplying a third overdrive voltage to the drive circuit of the LED in a third programming stage of the drive circuit that follows the second programming stage and precedes the steady-state programming stage, the third overdrive voltage being a third overvoltage that exceeds the steady-state voltage, and the third overvoltage being lower than the second overvoltage.

11. 11. The electronic device-implemented method of claim 10, wherein the reductions from the first overdrive voltage to the second overdrive voltage, from the second overdrive voltage to the third overdrive voltage, and from the third overdrive voltage to the steady-state voltage represent logarithmic voltage reductions.

12. activating the LEDs in the collection of LEDs includes:

12. A method performed by an electronic device according to any one of claims 1 to 11, comprising supplying the steady-state voltage to the driver circuit of the LED such that the data lines of the display emit at a steady-state light intensity over multiple successive frames of the display in multiple steady-state programming stages of the driver circuit following the steady-state programming stage.

13. Providing the first overdrive voltage to the drive circuit of the LED includes the data line delivering a first data voltage to the drive circuit during the first programming stage, the first data voltage being lower than a steady-state data voltage; providing the second overdrive voltage to the drive circuit of the LED includes the data line delivering a second data voltage to the drive circuit during the second programming phase, the second data voltage being higher than the first data voltage and lower than the steady-state data voltage; 13. A method performed by an electronic device according to any one of claims 1 to 12, wherein supplying the steady-state voltage to the drive circuit of the LED comprises the data line delivering the steady-state data voltage to the drive circuit during the steady-state programming phase.

14. the computing device presents video content at a first frame rate on the display; The method executed by the electronic device of any one of claims 1 to 13, wherein the computing device performs the supply of the first overdrive voltage and the supply of the second overdrive voltage at a second frame rate greater than the first frame rate.

15. The method performed by the electronic device of any one of claims 1 to 14, wherein the under-display sensor comprises an under-display fingerprint sensor.

16. 1. A computing device comprising: The display and an under-display sensor positioned below the display; and an electronic apparatus configured to cause the computing device to perform an operation, the operation comprising: receiving an instruction to activate the under-display sensor positioned below the display of the computing device; activating a collection of LEDs in the display to provide illumination to the under-display sensor; activating the LED collection includes activating LEDs in the LED collection, a data line of the display providing a first overdrive voltage to the driving circuit of the LED during a first programming phase of the driving circuit of the LED, the first overvoltage exceeding a steady-state voltage; the data lines of the display supplying a second overdrive voltage to the driver circuit of the LED in a second programming stage of the driver circuit following the first programming stage, the second overdrive voltage being a second overvoltage exceeding the steady-state voltage that is lower than the first overvoltage; the data lines of the display supplying the steady-state voltage to the driver circuits of the LEDs in a steady-state programming phase of the driver circuits subsequent to the first programming phase and the second programming phase; activating the LED by The operation is The computing device further includes activating the under-display sensor by reading a signal from the under-display sensor when the collection of LEDs is activated based on providing the steady-state voltage to the drive circuit of the LEDs.

17. A method implemented by an electronic device, comprising: receiving, at a computing device, instructions to activate an under-display fingerprint sensor positioned below a display of the computing device; activating a collection of LEDs in the display to illuminate the under-display fingerprint sensor; activating the LED collection includes activating LEDs in the LED collection, a data line of the display providing a first overdrive voltage to the driving circuit of the LED during a first programming phase of the driving circuit of the LED, the first overvoltage exceeding a steady-state voltage; the LED emitting a first light intensity that is less than a steady-state light intensity by a first deficit intensity in a first emission phase following the first programming phase; the data lines of the display supplying a second overdrive voltage to the driver circuit of the LED during a second programming phase of the driver circuit following the first emission phase, the second overdrive voltage being a second overvoltage above the steady-state voltage that is lower than the first overvoltage; the LED emitting a second light intensity, during a second emission phase following the second programming phase, that is weaker than the steady-state light intensity by a second deficit intensity that is less than the absolute amount of the first deficit intensity; the data lines of the display supplying the steady-state voltage to the driver circuits of the LEDs in a steady-state programming phase of the driver circuits following the second emission phase; the LED emitting the steady-state light intensity in a steady-state emission phase following the steady-state programming phase; supplying the steady-state voltage to the driver circuit of the LED such that the data lines of the display emit at a steady-state light intensity over a plurality of successive frames of the display in a plurality of steady-state programming stages of the driver circuit following the steady-state programming stage; activating the LED by The method comprises: The method executed by the electronic device further includes activating the under-display fingerprint sensor by reading a signal from the under-display fingerprint sensor when the collection of LEDs is activated, including when the LEDs emit the steady-state light intensity.

18. The method of claim 17, wherein providing the first overdrive voltage to the drive circuit of the LED includes the data line delivering a first data voltage to the drive circuit during the first programming phase, the first data voltage being lower than a steady-state data voltage; providing the second overdrive voltage to the drive circuit of the LED includes the data line delivering a second data voltage to the drive circuit during the second programming phase, the second data voltage being higher than the first data voltage and lower than the steady-state data voltage; 20. The electronic device-implemented method of claim 17, wherein supplying the steady-state voltage to the drive circuit of the LED includes the data line carrying the steady-state data voltage to the drive circuit during the steady-state programming phase.

19. 19. A method performed by an electronic device as described in claim 17 or 18, wherein the group of LEDs that are activated is a subset of all LEDs on the display that is positioned directly above the under-display fingerprint sensor.

20. the first programming step occurs during a first frame of the drive circuit; the second programming step occurs during a second frame of the drive circuit; 20. The electronic device implemented method of claim 17, wherein the second frame immediately follows the first frame such that the second programming stage is the immediately next programming stage following the first programming stage.

Images