LOCAL DIMMING FOR ARTIFICIAL REALITY SYSTEMS

1 . A method, implemented by a computing system, comprising:

receiving an image to be shown on a display of an artificial reality system, the display having a plurality of backlight zones;

computing a backlight matrix for adjusting brightness levels of the backlight zones of the display of the artificial reality system by:

for each of the backlight zones, computing a zone statistic to represent grayscale levels of a portion of the image within the backlight zone;

mapping the zone statistic of each of the backlight zones to a brightness value using a particular mapping technique configured to adjust any of the backlight zones having a zone statistic that is below a predetermined threshold; and

generating the backlight matrix by filtering the brightness values;

adjusting the brightness levels of the backlight zones of the display of the artificial reality system based on the backlight matrix; and

responsive to adjusting the brightness levels of the backlight zones, presenting the image on the display of the artificial reality system.

2 . The method of claim 1 , wherein prior to computing the zone statistic, generating a mipmap of the image, and wherein generating the mipmap of the image comprises:

downscaling the image to a reduced resolution.

3 . The method of claim 1 , wherein computing the zone statistic to represent the grayscale levels of the portion of the image within the backlight zone comprises:

computing, for each color component of a plurality of color components in the image, an average value of the color component across a plurality of pixels within the backlight zone; and

determining a maximum value among average values of the plurality of color components.

4 . The method of claim 3 , wherein the plurality of color components comprises red, green, and blue (RGB) color components.

5 . The method of claim 1 , wherein mapping the zone statistic of each of the backlight zones to the brightness value comprises:

determining backlight zones with zone statistics below the predetermined threshold; and

dimming the brightness levels of the determined backlight zones using the particular mapping technique.

6 . The method of claim 1 , wherein the predetermined threshold corresponds to low or dark grayscale levels.

7 . The method of claim 1 , wherein the particular mapping technique comprises a lookup table comprising predetermined brightness values corresponding to different zone statistics.

8 . The method of claim 1 , wherein the mapping results in an initial backlight matrix comprising of the brightness values for the backlight zones, wherein the initial backlight matrix comprises one or more artifacts.

9 . The method of claim 8 , wherein generating the backlight matrix by filtering the brightness values comprises:

performing spatial-temporal filtering to minimize the one or more artifacts in the initial backlight matrix.

10 . The method of claim 9 , wherein performing the spatial-temporal filtering to minimize the one or more artifacts in the initial backlight matrix comprises:

temporally filtering the brightness values in the initial backlight matrix based on a current frame and previous frames to minimize first artifacts; and

spatially filtering the brightness values in the initial backlight matrix based on neighboring backlight zones to minimize second artifacts.

11 . The method of claim 10 , wherein:

the first artifacts comprise backlight flickering artifacts due to head motion or moving objects; and

the second artifacts comprise over-dimming artifacts or halo effects.

12 . The method of claim 1 , wherein adjusting the brightness levels of the backlight zones of the display of the artificial-reality system comprises:

adjusting the brightness levels of the backlight zones of the display based on the brightness values in the backlight matrix.

13 . The method of claim 1 , wherein the brightness levels are adjusted without modifying color values of a plurality of color components in the image.

14 . (canceled)

15 . The method of claim 1 , wherein the artificial reality system is a virtual reality headset.

16 . The method of claim 1 , wherein the backlight matrix is computed by an algorithm running on a central processing unit (CPU) of the artificial reality system and without needing a dedicated hardware for computing the backlight matrix.

17 . One or more computer-readable non-transitory storage media embodying software that is operable when executed to:

receive an image to be shown on a display of an artificial reality system, the display having a plurality of backlight zones;

compute a backlight matrix for adjusting brightness levels of the backlight zones of the display of the artificial reality system by:

for each of the backlight zones, computing a zone statistic to represent grayscale levels of a portion of the image within the backlight zone;

mapping the zone statistic of each of the backlight zones to a brightness value using a particular mapping technique configured to adjust any of the backlight zones having a zone statistic that is below a predetermined threshold; and

generating the backlight matrix by filtering the brightness values;

adjust the brightness levels of the backlight zones of the display of the artificial reality system based on the backlight matrix; and

responsive to adjusting the brightness levels of the backlight zones, present the image on the display of the artificial reality system.

18 . The media of claim 17 , wherein prior to computing the zone statistic, the software is further operable when executed to generate a mipmap of the image, and wherein generating the mipmap of the image comprises:

downscaling the image to a reduced resolution.

19 . A system comprising:

one or more processors; and

one or more computer-readable non-transitory storage media coupled to one or more of the processors and comprising instructions operable when executed by one or more of the processors to cause the system to:

receive an image to be shown on a display of an artificial reality system, the display having a plurality of backlight zones;

compute a backlight matrix for adjusting brightness levels of the backlight zones of the display of the artificial reality system by:

for each of the backlight zones, computing a zone statistic to represent grayscale levels of a portion of the image within the backlight zone;

mapping the zone statistic of each of the backlight zones to a brightness value using a particular mapping technique configured to adjust any of the backlight zones having a zone statistic that is below a predetermined threshold; and

generating the backlight matrix by filtering the brightness values;

adjust the brightness levels of the backlight zones of the display of the artificial reality system based on the backlight matrix; and

responsive to adjusting the brightness levels of the backlight zones, present the image on the display of the artificial reality system.

20 . The system of claim 19 , wherein prior to computing the zone statistic, the one or more processors are further operable when executing the instructions to cause the system to generate a mipmap of the image, and wherein generating the mipmap of the image comprises:

downscaling the image to a reduced resolution.

21 . The method of claim 2 , wherein the downscaling of the image is based on at least a number of backlight zones of the display of the artificial reality system.