CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Swedish patent application No. 2250765-1, filed on 22 Jun. 2022, entitled “AN EYE TRACKING SYSTEM,” and is hereby incorporated by reference in its entirety.

FIELD

The present disclosure generally relates to the field of eye tracking. In particular, the present disclosure relates to controllers, algorithms, eye tracking systems and methods for improving the evenness with which a plurality of light sources illuminate a user's eye when the eye tracking system is in use.

BACKGROUND

In eye tracking applications, digital images are retrieved of the eyes of a user and the digital images are analysed in order to estimate gaze direction of the user. The estimation of the gaze direction may be based on computer-based image analysis of features of the imaged eye. One known example method of eye tracking includes the use of infrared light and an image sensor. The infrared light is directed towards eye(s) of a user and the reflection of the light is captured by an image sensor.

Many eye tracking systems estimate gaze direction based on identification of a pupil position together with glints or corneal reflections in the digital images. However, gaze estimation techniques can suffer from errors due to assumptions about the shape and/or position of the features of the eye. Therefore, improving the accuracy of such feature determination can be important for eye tracking systems and methods.

Portable or wearable eye tracking devices have been previously described. One such eye tracking system is described in U.S. Pat. No. 9,041,787 (which is hereby incorporated by reference in its entirety). A wearable eye tracking device is described using illuminators and image sensors for determining gaze direction.

SUMMARY

According to a first aspect of the present disclosure there is provided an eye tracking system comprising:

- a plurality of light sources that are arranged to illuminate a user's eye when the eye tracking system is in use; and
- a controller configured to:
  - receive a first-image of a surface, acquired while the surface is illuminated by a first set of the plurality of light sources;
  - receive a second-image of the surface, acquired while the surface is illuminated by a second set of the plurality of light sources, wherein the second set of light sources is different to the first set of light sources;
  - process the first-image and the second-image to determine an illumination contribution of one or more of the light sources; and
  - determine light-source-control-signalling for one or more of the light sources based on the determined illumination contribution of the one or more of the light sources, wherein the light-source-control-signalling is for setting the intensity of light provided by the respective light sources when the eye tracking system is in use.

Advantageously, setting the light-source-control-signalling in this way can enable the light sources to more evenly illuminate the user's eye when the eye tracking system is in use such that improved eye tracking can be achieved.

The first set of the plurality of light sources may comprise all of the light sources. The second set of the plurality of light sources may comprise a subset of the light sources. The controller may be configured to:

- process the first-image and the second-image to determine an illumination contribution of the light sources that are not included in the second set of the plurality of light sources; and
- determine light-source-control-signalling for the light sources that are not included in the second set of the plurality of light sources based on the determined illumination contribution of the light sources that are not included in the second set of the plurality of light sources.