Determining stylus location relative to projected whiteboard using secondary IR emitter on stylus

1. A device, comprising:

a processor;

an infrared (IR) detector accessible to the processor and that is configured to receive signals from a primary IR emitter on a hand-held device and a secondary IR emitter on the hand-held device;

a projector accessible to the processor;

a transceiver accessible to the processor;

storage accessible to the processor and bearing instructions executable by the processor to:

use a location of the secondary IR emitter as sensed by the IR detector and orientation data of the hand-held device received from the transceiver to extrapolate a handwriting projection reference;

use the handwriting projection reference to project handwriting onto a surface;

determine that the IR detector does not receive signals from the primary IR emitter on the hand-held device; and

responsive to determining that the IR detector does not receive signals from the primary IR emitter, transmit a signal to the hand-held device to activate the secondary IR emitter.

2. The device of claim 1 , wherein the instructions are executable by the processor to:

responsive to a determination that IR from the primary IR emitter is re-acquired, send a signal to the hand-held device to deactivate the secondary IR emitter.

3. The device of claim 1 , wherein the instructions are executable by the processor to:

use, to extrapolate the handwriting projection reference, a location of the secondary IR emitter as sensed by the IR detector, a distance between the primary IR emitter and the secondary IR emitter, and orientation data of the hand-held device received from the transceiver.

4. The device of claim 1 , wherein the handwriting projection reference is an extrapolated location of the primary IR emitter.

5. The device of claim 1 , wherein the orientation data is generated by a sensor on the hand-held device.

6. The device of claim 5 , wherein the sensor comprises at least one of the group consisting of: a gyroscope, a magnetometer.

7. The device of claim 1 , comprising the hand-held device.

8. A computer readable storage medium (CRSM) that is not a transitory signal, the computer readable storage medium comprising instructions executable by a processor to:

access, from a hand-held device, an orientation signal;

access, from an infrared (IR) detector, information indicating a location of a secondary IR emitter on the hand-held device, the hand-held device also having a primary IR emitter;

determine an extrapolated location LP of the primary emitter as being:

LP=LS+D(f(angle)), wherein LS is the location of the secondary IR emitter, angle is indicated in the orientation signal, “D” is a distance between the primary and secondary IR emitters, and “f” is a trigonometric function.

9. The CRSM of claim 8 , wherein the instructions are executable by the processor to:

determine that the IR detector does not receive signals from the primary IR emitter; and

responsive to determining that the IR detector does not receive signals from the primary IR emitter, transmit a signal to the hand-held device to activate the secondary IR emitter.

10. The CRSM of claim 9 , wherein the instructions are executable by the processor to:

responsive to a determination that IR from the primary IR emitter is re-acquired, send a signal to the hand-held device to deactivate the secondary IR emitter.

11. The CRSM of claim 8 , wherein the instructions are executable by the processor to:

use the extrapolated location LP of the primary emitter to project handwriting onto a projected whiteboard.

12. The CRSM of claim 8 , wherein the instructions are executable by the processor to:

use, to extrapolate the handwriting projection reference, a location of the secondary IR emitter as sensed by the IR detector, a distance between the primary IR emitter and the secondary IR emitter, and orientation data of the hand-held device received from a transceiver.

13. The CRSM of claim 8 , comprising the processor and the IR detector.

14. A method, comprising:

detecting, at a device and using an IR detector associated with a projector projecting onto a surface, a secondary infrared (IR) emitter on a stylus, the stylus further comprising a primary IR emitter;

receiving orientation data pertaining to the stylus;

projecting, using the detection of the secondary IR emitter and the orientation data, handwriting onto the surface;

using a location of the secondary IR emitter as sensed by the IR detector, a distance between the primary IR emitter and the secondary IR emitter, and the orientation data, extrapolating a handwriting projection reference.

15. The method of claim 14 , comprising:

determining that the primary IR emitter on the stylus is not detected by the IR detector; and

providing, responsive to determining that the primary IR emitter is not detected by the IR detector, a command to the stylus for the secondary IR emitter on the stylus to be activated.

16. The method of claim 15 , comprising:

responsive to a determination that IR from the primary IR emitter is re-acquired, providing a command to the stylus to deactivate the secondary IR emitter.

17. The method of claim 14 , wherein the handwriting projection reference is an extrapolated location of the primary IR emitter.

18. The method of claim 14 , wherein using a location of the secondary IR emitter as sensed by the IR detector, a distance between the primary IR emitter and the secondary IR emitter, and the orientation data comprises:

determining an extrapolated location LP of the primary emitter as being:

LP=LS+D(f(angle)), wherein LS is the location of the secondary IR emitter, angle is indicated in the orientation data, “D” is a distance between the primary and secondary IR emitters, and “f” is a trigonometric function.