Calibration of an eye tracking system

Patent metadata

Field	Value
Publication number	US-11568560-B2
Application number	US-202117242908-A
Country	US
Kind code	B2
Filing date	Apr 28, 2021
Priority date	Apr 28, 2020
Publication date	Jan 31, 2023
Grant date	Jan 31, 2023

Abstract

There is provided mechanisms for calibration of an eye tracking system. An eye tracking system comprises a pupil centre corneal reflection (PCCR) based eye tracker and a non-PCCR based eye tracker. A method comprises obtaining at least one first eye position of a subject by applying the PCCR based eye tracker on an image set depicting the subject. The method comprises calibrating a head model of the non-PCCR based eye tracker, as applied on the image set, for the subject using the obtained at least one first eye position from the PCCR based eye tracker as ground truth. The head model comprises facial features that include at least one second eye position. The calibrating involves positioning the head model in order for its at least one second eye position to be consistent with the at least one first eye position given by the PCCR based eye tracker.

First claim

The invention claimed is:

1. An eye tracking system, the eye tracking system comprising a pupil centre corneal reflection fPCCR) based eye tracker and a non-PCCR based eye tracker, wherein the PCCR based eye tracker is unable to track movement of at least one first eye position when a subject gazes at points located outside a circle, wherein the PCCR based eye tracker is used to track movement of the at least one first eye position of the subject when the subject gazes at points located inside the circle, and wherein the non-PCCR based eye tracker is used to track movement of at least one second eye position of the subject when the subject gazes at points located outside the circle, the eye tracking system being configured to:
obtain at least one first eye position of a subject by applying the PCCR based eye tracker on an image set depicting the subject; and
calibrate a head model of the non-PCCR based eye tracker, as applied on the image set, for the subject using the obtained at least one first eye position from the PCCR based eye tracker as ground truth, wherein the head model comprises facial features that include at least one second eye position, and wherein the calibrating involves positioning the head model in order for its at least one second eye position to be consistent with the at least one first eye position given by the PCCR based eye tracker.

2. The eye tracking system according to claim 1 , wherein the at least one first eye position is represented by cornea positions of the subject, and wherein the at least one second eye position is represented by pupil positions of the subject.

3. The eye tracking system according to claim 1 , further being configured to:
calculate gaze of the subject in the image set using the PCCR based eye tracker or the non-PCCR based eye tracker.

4. The eye tracking system according to claim 3 , further being configured to:
track movement of the at least one first eye position of the subject in the image set using the PCCR based eye tracker,
wherein the gaze of the subject is calculated using the tracked movement of the at least one first eye position of the subject using the PCCR based eye tracker.

5. The eye tracking system according to claim 3 , further being configured to:
track movement of the at least one second eye position of the subject in the image set using the non-PCCR based eye tracker,
wherein the gaze of the subject is calculated using the tracked movement of the at least one second eye position and/or head pose of the subject using the non-PCCR based eye tracker.

6. The eye tracking system according to claim 5 , wherein movement of the at least one second eye position of the subject in the image set is tracked using the non-PCCR based eye tracker when the PCCR based eye tracker is unable to track movement of the at least one first eye position.

7. The eye tracking system according to claim 6 , wherein the PCCR based eye tracker is determined to be unable to track movement of the at least one first eye position based at least on one of the following: by no glints being obtainable by the PCCR based eye tracker; more glints being obtainable by the PCCR based eye tracker than the number of illuminators illuminating an eye of the subject; and an illuminator pattern, introduced by the positions of the illuminators illuminating the eye, does not match a pattern of the glints in the eye of the subject.

8. The eye tracking system according to claim 1 , wherein positioning the head model to match its at least one second eye position to the at least one first eye position given by the PCCR based eye tracker involves any of rotating, translating, and/or scaling the head model.

9. The eye tracking system according to claim 1 , wherein calibrating the head model involves updating geometry parameters of the facial features.

10. An eye tracking system, the eye tracking system comprising a pupil centre corneal reflection (PCCR) based eye tracker and a non-PCCR based eye tracker, wherein the PCCR based eye tracker is unable to track movement of at least one first eye position when subject gazes at points located outside a circle, wherein the PCCR based eye tracker is used to track movement of the at least one first eye position of the subject when the subject gazes at points located inside the circle, and wherein the non-PCCR based eye tracker is used to track movement of at least one second eye position of the subject when the subject gazes at points located outside the circle, the eye tracking system further comprising:
an obtain module configured to obtain at least one first eye position of a subject by applying the PCCR based eye tracker on an image set depicting the subject; and
a calibrate module configured to calibrate a head model of the non-PCCR based eye tracker, as applied on the image set, for the subject using the obtained at least one first eye position from the PCCR based eye tracker as ground truth, wherein the head model comprises facial features that include at least one second eye position, and wherein the calibrating involves positioning the head model in order for its at least one second eye position to be consistent with the at least one first eye position given by the PCCR based eye tracker.

11. A vehicle comprising the eye tracking system according to claim 1 , wherein the subject is a driver or a passenger of the vehicle.

12. A method for calibration of an eye tracking system, the eye tracking system comprising a pupil centre corneal reflection (PCCR) based eye tracker and a non-PCCR based eye tracker, wherein the PCCR based eye tracker is unable to track movement of at least one first eye position when a subject gazes at points located outside a circle, wherein the PCCR based eye tracker is used to track movement of the at least one first eye position of the subject when the subject gazes at points located inside the circle, and wherein the non-PCCR based eye tracker is used to track movement of at least one second eye position of the subject when the subject gazes at points located outside the circle, the method comprising:
obtaining at least one first eye position of a subject by applying the PCCR based eye tracker on an image set depicting the subject; and
calibrating a head model of the non-PCCR based eye tracker, as applied on the image set, for the subject using the obtained at least one first eye position from the PCCR based eye tracker as ground truth, wherein the head model comprises facial features that include at least one second eye position, and wherein the calibrating involves positioning the head model in order for its at least one second eye position to be consistent with the at least one first eye position given by the PCCR based eye tracker.

13. The method according to claim 12 , further comprising:
calculating gaze of the subject in the image set using the PCCR based eye tracker or the non-PCCR based eye tracker.

14. The method according to claim 13 , further comprising:
tracking movement of the at least one first eye position of the subject in the image set using the PCCR based eye tracker,
wherein the gaze of the subject is calculated using the tracked movement of the at least one first eye position of the subject using the PCCR based eye tracker.

15. The method according to claim 13 , further comprising:
tracking movement of the at least one second eye position of the subject in the image set using the non-PCCR based eye tracker,
wherein the gaze of the subject is calculated using the tracked movement of the at least one second eye position and/or head pose of the subject using the non-PCCR based eye tracker.

Assignees

• Tobii Ab

Inventors

• Fogelström Per
• Redz Anna
• Dahl Anders
• Ollesson Niklas

Classifications

• G06T7/70 Primary

  Determining position or orientation of objects or cameras (camera calibration G06T7/80) · CPC title

• G06V40/193

  Preprocessing; Feature extraction · CPC title

• G06T2207/30201

  Face · CPC title

• G06V20/597

  Recognising the driver's state or behaviour, e.g. attention or drowsiness · CPC title

• G06T7/251 Primary

  involving models · CPC title