Systems and methods for presence detection
View Patent ↗Systems and methods are provided for presence detection using an image system. The image system may be a camera that is integrated into an electronic device. In some embodiments, the image system can accommodate multiple operating modes of the electronic device. For example, when the electronic device is operating in a normal power mode, control circuitry of the image system can detect when a user has left and is no longer using the electronic device. When the electronic device is operating in a power saving mode, the control circuitry can detect user presence (e.g., when a user has come back to the electronic device). In some embodiments, the control circuitry can adjust for both gradual and sudden light changes.
1. A method of performing presence detection, the method comprising:
selecting a first image frame as a reference frame, wherein the reference frame is divided into a first grid of zones, and wherein the first grid of zones is associated with a set of reference luminance values;
selecting a second image frame as a current frame, wherein the current frame is divided into a second grid of zones, and wherein the second grid of zones is associated with a set of current luminance values;
calculating a set of parameters between the set of reference luminance values and the set of current luminance values;
determining that at least one of the set of parameters satisfies a pre-determined threshold:
in response to the determining, performing one or more actions based at least in part of the at least one parameter and an operating mode of an electronic device;
monitoring at least one of a number of positively changed zones, a number of negatively changed zones, a number of changed zones, and a number of changed columns;
detecting if a sudden light change has occurred based at least in part on the number of positively changed zones, the number of negatively changed zones, and the number of changed zones; and
in response to detecting that the sudden light change has not occurred:
determining that an operating mode of an electronic device is a power saving mode;
determining that a number of changed zones is above a second zone threshold;
determining that a number of changed columns is above a column threshold; and
detecting user presence in close proximity to the electronic device.
2. The method of claim 1 , wherein the selecting the first image frame further comprises storing the set of reference luminance values.
3. The method of claim 1 , wherein the calculating the set of parameters comprises calculating an absolute differential between the set of current luminance values and the set of reference luminance values.
4. The method of claim 1 , wherein the calculating the set of parameters comprises calculating a percentage differential between the set of current luminance values and the set of reference luminance values.
5. The method of claim 1 , further comprising switching the operating mode, wherein the switching the operating mode comprises enabling the electronic device to enter a normal power mode.
6. The method of claim 5 , wherein the enabling the electronic device comprises:
adjusting a signal state of a control line to a power management circuitry of the electronic device; and
triggering the power management circuitry to wake up the electronic device.
7. The method of claim 1 , further comprising:
determining that a time-dependent counter has reached a counter threshold;
determining that a number of changed zones is within a number of zones threshold; and
selecting a third image frame as the reference frame.
8. An image system comprising:
an image sensor operative to calculate a set of luminance values;
an auto-exposure module for adjusting exposure of an image; and
control circuitry for performing presence detection, wherein the control circuitry is operative to:
disable the auto-exposure module while detecting user presence;
receive, from the image sensor, a set of reference luminance values corresponding to a reference frame and a set of current luminance values corresponding to a current frame;
calculate a set of parameters between the set of reference luminance values and the set of current luminance values;
determine that at least one parameter of the set of parameters satisfies a pre-determined threshold; and
in response to the determining, perform one or more actions based at least in part on the at least one parameter and an operating mode of an electronic device.
9. The image system of claim 8 , wherein each luminance value of the set of reference luminance values corresponds to each zone of a plurality of zones of a reference frame, and wherein each luminance value of the set of current luminance values corresponds to each zone of a plurality of zones of a current frame.
10. The image system of claim 8 , wherein the control circuitry is operative to monitor at least one of a number of positively changed zones, a number of negatively changed zones, a number of changed zones, and a number of changed columns.
11. The image system of claim 10 , wherein the control circuitry is operative to detect if a sudden light change has occurred based at least in part on the number of positively changed zones, the number of negatively changed zones, and the number of changed zones.
12. The image system of claim 11 , wherein the control circuitry is operative to:
determine that one of the number of positively changed zones and the number of negatively changed zones is equal to zero;
determine that the number of changed zones is above or equal to a high zone threshold; and
detect that the sudden light change has occurred.
13. The image system of claim 11 , wherein in response to detecting that the sudden light change has not occurred, the control circuitry is operative to:
determine that the operating mode of the electronic device is a normal power mode;
determine that the number of changed zones is greater than a first zone threshold; and
detect user presence in close proximity to the image system.
14. The image system of claim 11 , wherein in response to detecting that the sudden light change has not occurred, the control circuitry is further operative to:
determine that the operating mode of the electronic device is a power saving mode;
determine that the number of changed zones is above a second zone threshold;
determine that the number of changed columns is above a column threshold; and
detect user presence in close proximity to the image system.
15. The image system of claim 8 , wherein the control circuitry is operative to:
monitor exposure of the image;
determine if the exposure of the image satisfies at least a first condition;
in response to the determining, suspend the detection of user presence; and
enable the auto-exposure module.
16. The image system of claim 15 , wherein the control circuitry is operative to:
monitor an average luminance value of the image; and
determine that the average luminance value falls below a low luminance threshold or exceeds a high luminance threshold.
17. The image system of claim 15 , wherein the auto-exposure module is operative to adjust the exposure.
18. The image system of claim 17 , wherein the control circuitry is operative to:
determine if the exposure of the image satisfies at least a second condition;
disable the auto-exposure module;
receive, from the image sensor, a new set of reference luminance values corresponding to a new reference frame; and
resume the detection of user presence.