Rejecting display leakage light in under-display sensors
This document describes systems and directed at rejecting display leakage light in under-display sensors. In aspects, an ambient light sensor of an electronic device rejects leakage light originating from pixels in a display using a look-up table and an ambient light calculating formula. In implementations, the look-up table is developed based on a variety of operating conditions that the electronic device may experience, including variable refresh rates and display luminosities. The look-up table includes pre-calculated values of a leakage light ratio, for given operating conditions, that can be used to reject leakage light originating from displays by computing the ambient light calculating formula.
1. An electronic device comprising:
an under-display ambient light sensor configured to collect ambient light measurements;
a display comprising:
a pixel array including one or more pixel circuits, each pixel circuit of the one or more pixel circuits comprising a diode configured to illuminate; and
an emission control-line driver operably coupled to the pixel array, the emission control-line driver configured to:
supply, based on intended display operating conditions, a low emission-control signal and a high emission-control signal effective to cause at least portions pf the pixel array to illuminate and darken, respectively; and
a processor configured to:
receive ambient light measurements during the low emission-control signal and the high emission-control signal; and
calculate, based on display operating conditions and a look-up table, ambient light external to a display-side of the electronic device by rejecting leakage light originating from the pixel array, the processor configured to calculate ambient light using an ambient light formula:
L Y =α*L ON /α−1 −−L OFF /(α−1),
where ‘L Y ’ corresponds to the calculated ambient light, ‘a’ corresponds to the leakage light ratio, ‘L ON ’ corresponds to ambient light measurements during the low emission-control signal, and ‘L OFF ’ corresponds to ambient light measurements during the high emission-control signal.
2. The electronic device of claim 1 , wherein the look-up table comprises pre-calculated leakage light ratios for a variety of display operating conditions.
3. The electronic device of claim 2 , wherein the leakage light ratio is calculated during development of the look-up table on a second electronic device, the leakage light ratio based on a formula:
a=L X_OFF /L X_ON ,
where ‘a’ corresponds to the leakage light ratio, ‘L X_OFF ’ corresponds to ambient light measurements collected during a high emission-control signal on the second electronic device, and ‘L X_ON ’ corresponds to ambient light measurements collected during a low emission-control signal on the second electronic device.
4. The electronic device of claim 3 , wherein the processor is further configured to receive, prior to the receipt of ambient light measurements, the look-up table developed on the second electronic device.
5. The electronic device of claim 1 , wherein the processor is further configured to adjust, based on the calculated ambient light, a first brightness of the display to a second brightness, the second brightness smaller in luminosity than the first brightness and sufficient to promote viewing of on-screen content.
6. The electronic device of claim 1 , wherein the current operating conditions of the display include at least one of a display refresh rate or a display brightness.
7. The electronic device of claim 1 , wherein the processor is packaged with the under-display ambient light sensor.