Compensation for crosstalk between electronic display and ambient light sensor
An electronic display includes an ambient light sensor (ALS) located beneath an active area to sense ambient light above the active area. The ALS is synchronized with blanking periods of a display pixel on the active area. An emission-off scale factor is calculated based on an emission profile of the display pixel when the display pixel is turned off. The emission-off scale factor is used with display content to calculate a crosstalk compensation for the ALS.
1 . A method comprising:
operating an ambient light sensor of an electronic display to sense light signals during an integration period occurring after a time offset within an emission blanking period of a region of display pixels of the electronic display when emission from the region of display pixels of the electronic display is less than a threshold luminance value;
generating an emission-off scale factor for a display pixel of the electronic display at least in part based on a brightness level of the electronic display and a gray level of display content displayed at the display pixel, wherein the emission-off scale factor is indicative of an amount of light emission of the display pixel during the integration period of the ambient light sensor;
calculating a crosstalk compensation for the ambient light sensor using the emission-off scale factor; and
applying the crosstalk compensation to a reading of the ambient light sensor.
2 . The method of claim 1 , wherein the emission-off scale factor is generated for the brightness level by interpolating a plurality of calculated emission-off scale factor values.
3 . The method of claim 2 , wherein the emission-off scale factor is generated for the gray level by interpolating the plurality of calculated emission-off scale factor values.
4 . The method of claim 2 , wherein the plurality of calculated emission-off scale factor values are generated based on an emission profile of the region of display pixels when the region of display pixels is turned off.
5 . The method of claim 4 , wherein the plurality of calculated emission-off scale factor values are generated for one or more brightness levels of the electronic display.
6 . The method of claim 4 , wherein the plurality of calculated emission-off scale factor values are generated for one or more gray levels of the electronic display.
7 . The method of claim 4 , wherein the region of display pixels comprises an organic light emitting diode.
8 . An electronic device, comprising:
an ambient light sensor configured to detect measurements of ambient light for an electronic display coupled to the electronic device; and
circuitry configured to generate an emission-off scale factor, which is used to compensate the measurements of ambient light, by:
selecting a plurality of emission lookup tables based on a current brightness of the electronic display, wherein the plurality of emission lookup tables correspond to respective brightnesses of the electronic display;
interpolating the plurality of emission lookup tables to obtain an interpolated emission lookup table for the current brightness of the electronic display; and
generating the emission-off scale factor using the interpolated emission lookup table, wherein generating the emission-off scale factor comprises:
selecting a plurality of rows in the interpolated emission lookup table based on a gray level of the electronic display; and
interpolating the plurality of rows to obtain the emission-off scale factor.
9 . The electronic device of claim 8 , wherein the plurality of emission lookup tables comprise a plurality of calculated emission-off scale factors obtained based on an emission profile of a display pixel of the electronic display when the display pixel is turned off.
10 . The electronic device of claim 9 , wherein the display pixel comprise an organic light emitting diode (OLED).
11 . The electronic device of claim 9 , wherein the plurality of calculated emission-off scale factors are generated for a plurality of brightness levels of the electronic display.
12 . The electronic device of claim 9 , wherein the plurality of calculated emission-off scale factors are generated for a plurality of gray levels of the electronic display.
13 . The electronic device of claim 8 , wherein the electronic device comprises a handheld device, a notebook computer, a mobile phone, a tablet, a wearable device, a desktop computer, or any combination thereof.
14 . An electronic device comprising:
an active area of an electronic display;
an ambient light sensor configured to sense ambient light above the active area during an integration period occurring after a time offset within an emission blanking period of a region of display pixels of the electronic display when emission from the region of display pixels of the electronic display is less than a threshold luminance value; and
circuitry configured to:
generate an emission-off scale factor for a display pixel of the electronic display at least in part based on a brightness level of the electronic display and a gray level of display content displayed at the display pixel, wherein the emission-off scale factor is indicative of an amount of light emission of the display pixel during the integration period of the ambient light sensor;
calculate a crosstalk compensation for the ambient light sensor using the emission-off scale factor; and
apply the crosstalk compensation to a reading of the ambient light sensor.
15 . The electronic device of claim 14 , wherein the ambient light sensor is located beneath the region of display pixels.
16 . The electronic device of claim 14 , wherein a first portion of display pixels of the electronic display are on and emitting light and a second portion of the display pixels of the electronic display are off and are emitting residual light after previously being on.
17 . The electronic device of claim 16 , wherein the ambient light sensor is configured to receive residual light emission from the second portion of the display pixels.
18 . The electronic device of claim 17 , wherein the residual light emission from the second portion of the display pixels are estimated based on an emission profile of the display pixels.
19 . The electronic device of claim 18 , wherein the emission profile is associated with a global brightness level of the electronic display.
20 . The electronic device of claim 18 , wherein the emission profile is associated with a gray level of display content displayed on the electronic display.
21 . The electronic device of claim 18 , wherein the display pixels comprise an organic light emitting diode (OLED).