Adaptive Camera And Illuminator Eyetracker

• US 20130107214A1
• Filed: 12/17/2012
• Published: 05/02/2013
• Est. Priority Date: 04/01/2009
• Status: Active Grant

• Current Assignee: Tobii Technology AB
• Original Assignee: Tobii Technology AB
• Inventors: BLIXT, PETER, Troili, Gunnar, Elvesj, John Mikael, Skog, Mrten, Hglund, Anders
• Granted Patent: US 8,944,600 B2
• Time in Patent Office: Days
• US Class Current: 351/210
• CPC Class Codes: A61B 3/0008 provided with illuminating means A61B3/117 takes precedence; goniolenses used for laser treatment A61F9/009; illuminating means for optical instruments G02B27/00
• CPC Class Codes: A61B 3/0025 characterised by electronic signal processing, e.g. eye models
• CPC Class Codes: A61B 3/113 for determining or recording eye movement
• CPC Class Codes: A61B 3/14 Arrangements specially adapted for eye photography apparatus or arrangements for taking photographs per se G03B
• CPC Class Codes: A61B 3/145 by video means
• CPC Class Codes: G06V 40/19 Sensors therefor

Abstract

An eye tracker includes at least one illuminator for illuminating an eye, at least two cameras for imaging the eye and a controller. The configuration of the reference illuminator and cameras is such that, at least one camera is coaxial with a reference illuminator and at least one camera is non-coaxial with a reference illuminator. The controller selects one of the cameras to be active to increase an image quality metric and avoid obscuring objects. The eye tracker is operable in a dual-camera mode to improve accuracy.

Claims

1. An eye tracker comprising:

at least one reference illuminator for illuminating an eye;

a plurality of cameras for imaging the eye, with at least one camera being arranged coaxially with said at least one reference illuminator, and with at least one other camera being arranged non-coaxially with said at least one reference illuminator; and

a controller configured to repeatedly evaluate an image quality metric based on at least one image quality factor for images provided by said at least one camera and said at least one other camera, and to select said at least one camera or said at least one other camera to be active based on the image quality metric.

2. The eye tracker according to claim 1, wherein said at least one reference illuminator comprises a plurality of reference illuminators.

3. The eye tracker according to claim 2, wherein each camera is associated with a coaxial and substantially point-shaped illuminator of said at least plurality of reference illuminators.

4. The eye tracker according to claim 2, wherein said controller is further configured to repeatedly select a combination of one of said at least one camera and said at least one other camera to be active, based on the image quality metric and a centric location of a corneo-scleral reflection.

5. The eye tracker according to claim 1, wherein said controller is configured to select said at least one camera and said at least one other camera so that the eye tracker is operate in a dual-camera mode.

6. The eye tracker according to claim 5, wherein said plurality of cameras are separated by 70 mm or more.

7. The eye tracker according to claim 5, wherein said controller is further configured to determine a location of a first Purkinje reflection based on two images acquired simultaneously by different cameras in the dual-camera mode.

8. The eye tracker according to claim 2, wherein said controller is operable in an evaluation mode and activates said at least one camera and said at least one other camera while sequentially scanning the plurality of reference illuminators.

9. The eye tracker according to claim 1, wherein said at least one reference illuminator is configured to emit at least one of infrared light and near-infrared light.

10. The eye tracker according to claim 2, wherein said controller is further configured to determine a gaze direction of the eye based on locations of corneo-scleral reflections of said at least one reference illuminator.

11. The eye tracker according to claim 2, further comprising a processor configured to:

define a mapping between a coordinate system in an object coordinate plane and a coordinate system in a plane of an eye image based on locations in the eye image of corneo-scleral reflections of said plurality of reference illuminators; and

determine, based on the mapping, a gaze point of the eye in the object coordinate system;

with the mapping comprising an ellipsoidal reflection mapping and a perspective projection.

12. The eye tracker according to claim 1, wherein the at least one image quality factor comprises at least one of a number of detected pupils, a gaze-detection noise, a pupil contrast, a gradient of pupil-iris boundary, a presence of obstacles, and a signal-to-noise ratio.

13. A method for selecting a combination of an active illuminator from a plurality of reference illuminators for illuminating an eye and an active camera from a plurality of cameras for imaging the eye, with at least one combination comprising an illuminator and a camera which are coaxial, and with at least one combination comprises an illuminator and a camera which are non-coaxial, the method comprising:

a) defining an image quality metric based on at least one image quality factor;

b) selecting an imaging mode based on values of the image quality metric for at least two eye images, with one of the eye images being obtained using a coaxial combination and with the other eye image being obtained using a non-coaxial combination;

c) selecting an active camera based on values of the image quality metric for eye images acquired using combinations according to the selected imaging mode; and

d) selecting an active reference illuminator based on the centricity of a corneo-scleral reflection of each reference illuminator from the plurality of reference illuminators.

14. The method according to claim 13, further comprising the sequential steps of:

e) if the at least one image quality factor is below a predetermined level, performing steps c) and d) and then, if the at least one image quality factor is still below the predetermined level, further performing steps b) and c); and

f) performing step d).

15. The method according to claim 13, wherein the at least one image quality factor comprises at least one of a number of detected pupils, a gaze-detection noise, a pupil contrast, a gradient of pupil-iris boundary, a presence of obstacles, and a signal-to-noise ratio.

16. A non-transitory computer-readable medium having computer executable instructions for causing an eye tracker to perform steps comprising:

selecting a combination of an active illuminator from a plurality of reference illuminators for illuminating an eye and an active camera from a plurality of cameras for imaging the eye, with at least one combinetion comprising an illuminator and a camera which are coaxial, and with at least one combination comprises an illuminator and a camera which are non-coaxial, the selecting comprising

a) defining an image quality metric based on at least one image quality factor;

b) selecting an imaging mode based on values of the image quality metric for at least two eye images, with one of the eye images being obtained using a coaxial combination and with the other eye image being obtained using a non-coaxial combination;

c) selecting an active camera based on values of the image quality metric for eye images acquired using combinations according to the selected imaging mode; and

d) selecting an active reference illuminator based on the centricity of a corneo-scleral reflection of each reference illuminator from the plurality of reference illuminators.

17. The non-transitory computer-readable medium according to claim 16, further comprising the sequential steps of:

e) if the at least one image quality factor is below a predetermined level, performing steps c) and d) and then, if the at least one image quality factor is still below the predetermined level, further performing steps b) and c); and

f) performing step d).

18. The non-transitory computer-readable medium according to claim 16, wherein the at least one image quality factor comprises at least one of a number of detected pupils, a gaze-detection noise, a pupil contrast, a gradient of pupil-iris boundary, a presence of obstacles, and a signal-to-noise ratio.