Brightness control for under-display sensor
Methods, systems, and apparatus, including computer programs encoded on computer storage media, for brightness control for under-display fingerprint sensor are disclosed. A method includes receiving, at a computing device, an indication to activate an under-display sensor that is located underneath a display of the computing device; activating a collection of LEDs of the display to provide illumination for the under-display sensor, including activating an LED in the collection of LEDs by: establishing, by drive circuitry of the LED, a first overdriven voltage across an LED-driving transistor that is arranged to energize the LED; establishing a second overdriven voltage across the LED-driving transistor; and establishing a steady state voltage across the LED-driving transistor; and activating the under-display sensor by reading a signal from the under-display sensor once the collection of LEDs has activated, including once the steady state voltage has been programmed across the LED-driving transistor.
1. A method, comprising:
providing, with a data line of a display during a programming stage of each of multiple first contiguous frames, an initial steady state voltage to a pixel circuit for a pixel of the display, to cause an LED of the pixel circuit to emit light at a first light intensity for the multiple first contiguous frames;
receiving an indication to activate an under-display sensor that is located underneath the display;
providing, with the data line of the display during a programming stage of an intermediate frame that follows the multiple first contiguous frames, responsive to receiving the indication to activate the under-display sensor, an overdriven voltage to the pixel circuit, to cause the LED of the pixel circuit to emit light at a second light intensity that is greater than the first light intensity;
providing, with the data line of the display during a programming stage of a second intermediate frame that follows the intermediate frame, a second overdriven voltage to the pixel circuit, the second overdriven voltage being between the overdriven voltage and a second steady state voltage, the second steady state voltage being between the initial steady state voltage and the overdriven voltage, a voltage difference between the second overdriven voltage and the second steady state voltage being less than a voltage difference between the overdriven voltage and the second steady state voltage;
providing, with the data line of the display during a programming stage of each of multiple second contiguous frames that follow the second intermediate frame, the second steady state voltage that is between the initial steady state voltage and the overdriven voltage, to cause the LED of the pixel circuit to emit light at a third light intensity that is greater than the first light intensity, for the multiple second contiguous frames; and
activating the under-display sensor, including reading a signal from the under-display sensor during the multiple second contiguous frames.
2. The method of claim 1 , wherein:
the pixel is included in a subset of all pixels of the display, with the subset comprising pixels that are located directly over the under-display sensor.
3. The method of claim 1 , wherein the under-display sensor comprises an under-display fingerprint sensor.
4. The method of claim 1 , wherein:
receiving the indication to activate the under-display sensor includes receiving an indication of user contact with the display at a user-contacted location that corresponds to a location of the under-display sensor.
5. The method of claim 1 , comprising:
determining a difference between the first light intensity and the third light intensity; and
selecting the overdriven voltage based on the difference between the first light intensity and the third light intensity, including:
selecting a larger overdriven voltage when the difference between the first light intensity of the LED and the third light intensity is greater; and
selecting a smaller overdriven voltage when the difference between the first light intensity of the LED and the third light intensity is lesser.
6. The method of claim 1 , comprising:
providing, with the data line of the display during a programming stage of a third intermediate frame that follows the second intermediate frame, a third overdriven voltage to the pixel circuit, the third overdriven voltage being between the second overdriven voltage and the second steady state voltage, a voltage difference between the third overdriven voltage and the second steady state voltage being less than the voltage difference between the second overdriven voltage and the second steady state voltage.
7. The method of claim 6 , wherein:
a decline from the overdriven voltage to the second overdriven voltage to the third overdriven voltage to the second steady state voltage represents a logarithmic voltage decline.
8. The method of claim 1 , wherein:
a computing device is configured to present video content on the display by energizing the LED through a dynamic range that extends from a minimum intensity to a maximum intensity; and
the maximum intensity is the same as the third light intensity.
9. The method of claim 1 , wherein:
a computing device presents video content with the display at a first frame rate; and
the computing device performs the providing the overdriven voltage to the pixel circuit and the providing the second overdriven voltage to the pixel circuit at a second frame rate that is greater than the first frame rate.
10. A computing device, comprising:
a display;
an under-display sensor that is located underneath the display; and
electronics that are configured to cause the computing device to perform operations that include:
providing, with a data line of the display during a programming stage of each of multiple first contiguous frames, an initial steady state voltage to a pixel circuit for a pixel of the display, to cause an LED of the pixel circuit to emit light at a first light intensity for the multiple first contiguous frames;
receiving an indication to activate the under-display sensor that is located underneath the display;
providing, with the data line of the display during a programming stage of an intermediate frame that follows the multiple first contiguous frames, responsive to receiving the indication to activate the under-display sensor, an overdriven voltage to the pixel circuit, to cause the LED of the pixel circuit to emit light at a second light intensity that is greater than the first light intensity;
providing, with the data line of the display during a programming stage of a second intermediate frame that follows the intermediate frame, a second overdriven voltage to the pixel circuit, the second overdriven voltage being between the overdriven voltage and a second steady state voltage, the second steady state voltage being between the initial steady state voltage and the overdriven voltage, a voltage difference between the second overdriven voltage and the second steady state voltage being less than a voltage difference between the overdriven voltage and the second steady state voltage;
providing, with the data line of the display during a programming stage of each of multiple second contiguous frames that follow the second intermediate frame, the second steady state voltage that is between the initial steady state voltage and the overdriven voltage, to cause the LED of the pixel circuit to emit light at a third light intensity that is greater than the first light intensity, for the multiple second contiguous frames; and
activating the under-display sensor, including reading a signal from the under-display sensor during the multiple second contiguous frames.
11. The computing device of claim 10 , wherein:
the pixel is included in a subset of all pixels of the display, with the subset comprising pixels that are located directly over the under-display sensor.
12. A display system, comprising:
a display;
an under-display sensor that is located underneath the display; and
electronics that are configured to cause the display system to perform operations that include:
providing, with a data line of the display during a programming stage of each of multiple first contiguous frames, an initial steady state voltage to a pixel circuit for a pixel of the display, to cause an LED of the pixel circuit to emit light at a first light intensity for the multiple first contiguous frames;
receiving an indication to activate the under-display sensor that is located underneath the display;
providing, with the data line of the display during a programming stage of an intermediate frame that follows the multiple first contiguous frames, responsive to receiving the indication to activate the under-display sensor, an overdriven voltage to the pixel circuit, to cause the LED of the pixel circuit to emit light at a second light intensity that is greater than the first light intensity;
providing, with the data line of the display during a programming stage of a second intermediate frame that follows the intermediate frame, a second overdriven voltage to the pixel circuit, the second overdriven voltage being between the overdriven voltage and a second steady state voltage, the second steady state voltage being between the initial steady state voltage and the overdriven voltage, a voltage difference between the second overdriven voltage and the second steady state voltage being less than a voltage difference between the overdriven voltage and the second steady state voltage;
providing, with the data line of the display during a programming stage of each of multiple second contiguous frames that follow the second intermediate frame, the second steady state voltage that is between the initial steady state voltage and the overdriven voltage, to cause the LED of the pixel circuit to emit light at a third light intensity that is greater than the first light intensity, for the multiple second contiguous frames; and
activating the under-display sensor, including reading a signal from the under-display sensor during the multiple second contiguous frames.
13. The method of claim 1 , comprising providing the overdriven voltage to the pixel circuit during an emission-off period of the LED.
14. The method of claim 1 , comprising providing the second steady state voltage to the pixel circuit during an emission-off period of the LED, wherein
the LED emits the light at the third light intensity during an emission stage that follows the emission-off period.
15. The method of claim 1 , wherein the third light intensity corresponds to the second light intensity.
16. The method of claim 1 , wherein providing the overdriven voltage to the pixel circuit before providing the second steady state voltage to the pixel circuit reduces stabilization time of the LED at the third light intensity, compared to stabilization time of the LED at the third light intensity that would result from the data line of the display providing the second steady state voltage to the pixel circuit without beforehand providing the overdriven voltage to the pixel circuit.
17. The method of claim 1 , wherein the LED emitting light at the third light intensity provides greater illumination for the under-display sensor compared to the LED emitting light at the first light intensity.
18. The computing device of claim 10 , wherein the third light intensity corresponds to the second light intensity.
19. The computing device of claim 10 , wherein providing the overdriven voltage to the pixel circuit before providing the second steady state voltage to the pixel circuit reduces stabilization time of the LED at the third light intensity, compared to stabilization time of the LED at the third light intensity that would result from the data line of the display providing the second steady state voltage to the pixel circuit without beforehand providing the overdriven voltage to the pixel circuit.
20. The method of claim 1 , wherein the method comprises activating the pixel to provide illumination for the under-display sensor, the method comprising:
activating a subset of all pixels of the display to provide illumination for the under-display sensor, wherein the subset of pixels that is activated is located directly over the under-display sensor.