Gaze tracking apparatus and systems

1. A system configured to perform an eye tracking process using a head-mountable eye-tracking arrangement, the system comprising:

an eye tracking unit, located on the head-mountable arrangement, operable to detect motion of one or both of the user's eyes;

a relative motion identification unit operable to identify motion of the head-mountable arrangement relative to the user's head; and

a correction unit operable to determine a correction to the eye tracking process in dependence upon the identified motion of the user's head relative to the head-mountable arrangement,

wherein the relative motion identification unit is operable to input one or more measurements into a model used to predict or estimate relative motion between the head-mountable arrangement and the user's head, and to use the predicted or estimated relative motion as the identified motion.

2. The system of claim 1 , the system comprising one or more sensors operable to detect one or both of motion of the user's head and motion of the head-mountable arrangement.

3. The system of claim 2 , wherein the sensors include one or more of a shear sensor, one or more cameras for tracking predetermined features, capacitive sensors, and/or a vibration sensor.

4. The system of claim 1 , comprising a head motion detection unit operable to detect motion of the user's head.

5. The system of claim 1 , comprising a head-mountable arrangement motion detection unit operable to detect motion of the head-mountable arrangement.

6. The system of claim 1 , wherein the correction unit is operable to modify the results of a detection of the user's eye position in dependence upon the determined correction.

7. The system of claim 6 , wherein the correction unit is operable to apply a correction to each of the user's eyes individually.

8. The system of claim 1 , wherein the correction unit is operable to generate a modified input to an application in dependence upon the determined correction.

9. The system of claim 1 , wherein the relative motion identification unit is operable to identify two or more values for the relative motion each corresponding to different respective methods of determining the relative motion.

10. The system of claim 1 , wherein the relative motion identification unit is operable to identify an expected relative motion in dependence upon content to be displayed to a user via a display device.

11. The system of claim 1 , wherein the head-mountable arrangement is a head-mountable display unit.

12. A method for performing an eye tracking process using a head-mountable eye-tracking arrangement, the method comprising:

detecting motion of one or both of the user's eyes;

identifying motion of the head-mountable arrangement relative to the user's head; and

determining a correction to the eye tracking process in dependence upon the identified motion of the user's head relative to the head-mountable arrangement,

wherein the identifying motion includes inputting one or more measurements into a model used to predict or estimate relative motion between the head-mountable arrangement and the user's head, and using the predicted or estimated relative motion as the identified motion.

13. A non-transitory machine-readable storage medium which stores computer software which, when executed by a computer, causes the computer to perform a method for performing an eye tracking process using a head-mountable eye-tracking arrangement, the method comprising:

detecting motion of one or both of the user's eyes;

identifying motion of the head-mountable arrangement relative to the user's head; and

determining a correction to the eye tracking process in dependence upon the identified motion of the user's head relative to the head-mountable arrangement,

wherein the identifying motion includes inputting one or more measurements into a model used to predict or estimate relative motion between the head-mountable arrangement and the user's head, and using the predicted or estimated relative motion as the identified motion.