Periodic parameter estimation for visual-inertial tracking systems

1. A method for calibrating a visual-inertial tracking system comprising:

detecting, at a head-mounted device, that a virtual object display application that is configured to operate at the head-mounted device is not requesting tracking operations from the visual-inertial tracking system of the head-mounted device;

in response to the detection, operating, at the head-mounted device, the visual-inertial tracking system

by accessing sensor data from a plurality of sensors only at the head-mounted device;

identifying, at the head-mounted device, a first calibration parameter value of the visual-inertial tracking system based on the sensor data from the plurality of sensors only at the head-mounted device;

storing, in a storage of the head-mounted device, the first calibration parameter value;

detecting an operation of the virtual object display application at the head-mounted device by detecting a tracking request from the virtual object display application to the visual-inertial tracking system; and

in response to detecting the tracking request, accessing, at the storage of the head-mounted device, the first calibration parameter value and determining, at the head-mounted device, a second calibration parameter value of the virtual-inertial tracking system from the first calibration parameter value.

2. The method of claim 1 , wherein operating the visual-inertial tracking system further comprises:

periodically accessing the sensor data from the plurality of sensors,

wherein the visual-inertial tracking system operates independently from the virtual object display application.

3. The method of claim 1 , further comprising:

detecting a calibration trigger event at the head-mounted device,

wherein operating the visual-inertial tracking system is in response to detecting the calibration trigger event.

4. The method of claim 3 , wherein the trigger event comprises at least one of a temperature change exceeding a temperature threshold, an accelerometer sensor value exceeding an accelerometer threshold value, a battery level of the device exceeding a battery threshold value, a user-activation of the head-mounted device, or a detection that the head-mounted device is worn by a user.

5. The method of claim 1 , wherein identifying the first calibration parameter value is based on a convergence between a first virtual object data point location and a second virtual object data point location, the first virtual object data point location being determined based on the sensor data that are adjusted with the first parameter value, the second virtual object data point location being determined based on the sensor data that are adjusted with a default calibration parameter value of the head-mounted device.

6. The method of claim 1 , further comprising:

turning off the visual-inertial tracking system after storing the first calibration parameter value; and

activating the visual-inertial tracking system in response to detecting an operation of the virtual object display application.

7. The method of claim 1 , further comprising:

calibrating the visual-inertial tracking system with the first calibration parameter value before operating the virtual object display application.

8. The method of claim 1 , further comprising:

calibrating the visual-inertial tracking system with the second calibration parameter value after detecting the tracking request from the virtual object display application.

9. The method of claim 1 , wherein determining the second calibration parameter value further comprises:

replacing a starting value comprising a default calibration value with the first calibration parameter value; and

performing a calibration of the visual-inertial tracking system starting with the starting value.

10. The method of claim 1 , wherein storing the first calibration parameter value further comprises:

storing the first calibration value in at a server.

11. A computing apparatus comprising:

a processor; and

a memory storing instructions that, when executed by the processor, configure the apparatus to perform operations comprising:

detect, at a head-mounted device, that a virtual object display application that is configured to operate at the head-mounted device is not requesting tracking operations from the visual-inertial tracking system of the head-mounted device;

in response to the detection, operate, at the head-mounted device, the visual-inertial tracking system

by accessing sensor data from a plurality of sensors only at the head-mounted device;

identify, at the head-mounted device, a first calibration parameter value of the visual-inertial tracking system based on the sensor data from the plurality of sensors only at the head-mounted device;

store, in a storage of the head-mounted device, the first calibration parameter value;

detect an operation of the virtual object display application at the head-mounted device by detecting a tracking request from the virtual object display application to the visual-inertial tracking system; and

in response to detecting the tracking request, access, at the storage of the head-mounted device, the first calibration parameter value and determining, at the head-mounted device, a second calibration parameter value of the virtual-inertial tracking system from the first calibration parameter value.

12. The computing apparatus of claim 11 , wherein operating the visual-inertial track system further comprises:

periodically access the sensor data from the plurality of sensors,

wherein the visual-inertial track system operates independently from the virtual object display application.

13. The computing apparatus of claim 11 , wherein the instructions further configure the apparatus to:

detect a calibration trigger event at the head-mounted device,

wherein operating the visual-inertial track system is in response to detecting the calibration trigger event.

14. The computing apparatus of claim 13 , wherein the trigger event comprises at least one of a temperature change exceeding a temperature threshold, an accelerometer sensor value exceeding an accelerometer threshold value, a battery level of the head-mounted device exceeding a battery threshold value, a user-activation of the head-mounted device, or a detection that the head-mounted device is worn by a user.

15. The computing apparatus of claim 11 , wherein identifying the first calibration parameter value is based on a convergence between a first virtual object data point location and a second virtual object data point location, the first virtual object data point location being determined based on the sensor data that are adjusted with the first parameter value, the second virtual object data point location being determined based on the sensor data that are adjusted with a default calibration parameter value of the head-mounted device.

16. The computing apparatus of claim 11 , wherein the instructions further configure the apparatus to:

turn off the visual-inertial tracking system after storing the first calibration parameter value; and

activating the visual-inertial tracking system in response to detecting an operation of the virtual object display application.

17. The computing apparatus of claim 11 , wherein the instructions further configure the apparatus to:

calibrate the visual-inertial tracking system with the first calibration parameter value before operating the virtual object display application.

18. The computing apparatus of claim 11 , wherein the instructions further configure the apparatus to:

calibrate the visual-inertial tracking system with the second calibration parameter value after detecting the tracking request from the virtual object display application.

19. The computing apparatus of claim 11 , wherein determining the second calibration parameter value further comprises:

replace a starting value comprising a default calibration value with the first calibration parameter value; and

perform a calibration of the visual-inertial tracking system starting with the starting value.

20. A non-transitory computer-readable storage medium, the computer-readable storage medium including instructions that when executed by a computer, cause the computer to perform operations comprising:

detect, at a head-mounted device, that a virtual object display application that is configured to operate at the head-mounted device is not requesting tracking operations from the visual-inertial tracking system of the head-mounted device;

in response to the detection, operate, at the head-mounted device, the visual-inertial tracking system

by accessing sensor data from a plurality of sensors only at the head-mounted device;

identify, at the head-mounted device, a first calibration parameter value of the visual-inertial tracking system based on the sensor data from the plurality of sensors only at the head-mounted device;

store, in a storage of the head-mounted device, the first calibration parameter value;

detect an operation of the virtual object display application at the head-mounted device by detecting a tracking request from the virtual object display application to the visual-inertial tracking system; and

in response to detecting the tracking request, access, at the storage of the head-mounted device, the first calibration parameter value and determining, at the head-mounted device, a second calibration parameter value of the virtual-inertial tracking system from the first calibration parameter value.