Power management in an eye-tracking system

1. A personal computer system comprising:

a visual display;

an imaging device, comprising one or more cameras and being adapted to provide eye-tracking data by imaging at least one eye of a viewer of the visual display; and

an input device configured to accept eye-tracking control data and other input data,

wherein:

the imaging device is switchable between at least an active mode, a ready mode and an idle mode;

the switching time from the idle mode to the active mode is longer than the switching time from the ready mode to the active mode;

the imaging device is configured to use active eye illumination in the active mode, which enables tracking of a corneal reflection; and

the imaging device is configured, in the ready mode, to reduce an illumination intensity from the value it has in active mode, and to provide eye-tracking data which include eye position but not eye orientation.

2. The personal computer system of claim 1 , wherein the active mode and the ready mode differ with respect to an operating frequency of the imaging device.

3. The personal computer system of claim 1 , wherein:

the eye-tracking data which the imaging device is configured to provide in the active mode include eye position and eye orientation.

4. The personal computer system of claim 1 , wherein:

the imaging device is configured to disable active eye illumination in the ready mode.

5. The personal computer system of claim 1 , wherein the eye-tracking data which the imaging device is configured to track, in the ready mode, relate to an eye location in an image plane but not in world coordinates.

6. The personal computer system of claim 1 , wherein the imaging device is configured to activate, in the active mode, at least one additional unit selected from the group comprising:

camera, and

light source,

wherein said at least one additional unit is disabled in the ready mode.

7. The personal computer system of claim 1 , wherein the imaging device is configured to pre-process optical data by binning at a higher binning ratio in the ready mode than in the active mode.

8. The personal computer system of claim 1 , wherein the input device includes:

at least one dedicated input device configured to accept eye-tracking control data only; and

at least one general-purpose input device configured to accept at least said other input data.

9. The personal computer system of claim 8 , wherein the dedicated input device forces the imaging device into active mode.

10. The personal computer system of claim 9 , wherein the dedicated input device forces the imaging device into active mode by directly triggering an interrupt.

11. The personal computer system of claim 8 , wherein the dedicated input device is a hardware touch-actuated input device configured to force the imaging device into idle mode.

12. The personal computer system of claim 11 , wherein:

the imaging device is selectively connected to drive power; and

the dedicated input device forces the imaging device into idle mode by disconnecting the imaging device from said drive power.

13. The personal computer system of claim 1 , further comprising a viewer presence detector configured to provide at least one of:

a positive detection signal causing the imaging device to switch from idle mode into ready mode;

a negative detection signal causing the imaging device to switch from active mode into idle mode;

a negative detection signal causing the imaging device to switch from ready mode into idle mode.

14. The personal computer system of claim 13 , wherein:

the viewer presence detector is a proximity sensor at a push button and is arranged to sense proximity of a finger; and

the proximity sensor is configured to provide a positive detection signal causing the image device to switch from idle mode into ready mode.

15. A method in a personal computer system comprising:

a visual display;

an imaging device, comprising one or more cameras and being adapted to provide eye-tracking data by imaging at least one eye of a viewer of the visual display; and

an input device configured to accept eye-tracking control data and other input data, said method comprising the steps of:

switching the imaging device between at least an active mode, a ready mode and an idle mode, wherein the switching time from the idle mode to the active mode is longer than the switching time from the ready mode to the active mode;

in the active mode of the imaging device, using active eye illumination, which enables tracking of a corneal reflection; and

in the ready mode of the imaging device, reducing an illumination intensity from the value it has in active mode, and providing eye-tracking data which include eye position but not eye orientation.

16. The method of claim 15 , further comprising the step of disabling active eye illumination in the ready mode.

17. The method of claim 15 , wherein the ready mode and the active mode differ with respect to a binning ratio, said binning ratio being higher in the ready mode than in the active mode.

18. A computer program product embodied on a non-transitory computer readable medium, the computer program product comprising computer-executable instructions of executing the method of claim 15 .

19. The method of claim 15 , further comprising the step of providing, in the active mode of the imaging device, eye-tracking data which include eye position and eye orientation.