Head Tracking with Cliffs of Dover

[SEE]

Originally Posted by Blackdog_kt

IR wavelengths carry less energy than our everyday normal, visible light.

I don't want to go into the technical details but IR LED's are safe to use and found in a large number of everyday items. Bear in mind that the recommended IR LED's also have a very wide beam angle. The reason for using IR LED's as opposed to visible light LED's (which also emit IR but less of it) is to enable users to mask the lens from visible light and the tracking is limited to 'heat signature'. To work effectively with IR, the camera also needs to have the IR filter removed (this in itself illustrates just how much IR forms part of natural light to put it simply).
Even with the lens masked off, point the camera to your window (not the Sun!) on a sunny day and compare the IR dots with the stray reflections and direct light entering through the window- it will be significantly higher and completely kill the tracking function by swamping. Alternatively, light a candle and hold it from a distance in front of the camera..........there will be significantly higher heat signature than from an IR LED.

Finally, if building your own IR Clip there is absolutely no need to run your IR LED's at full power. Run them at 50/70% of the stated current and connect them in series (one after the other like Xmas tree lights where one pops and all go out), your batteries will last three times longer or, once it's all working and well made in terms of your wiring/soldering skills, connect the clip to the USB port.