IR retinal safety

1 min read

At the moment all software work is paused until we have the hardware ability to track the eyes as we desire. Part of this process is to ensure, in our specification of the eye tracking cameras, that we do not produce too much infra-red radiation (in the LEDs we use to both illuminate and help track the position of the eyes) that it causes a health risk.

Given that this is open-hardware, let’s keep sharing information! One of the most helpful resources we’ve found is here https://www.renesas.com/eu/en/doc/application-note/an1737.pdf

Although the IR LED’s we are selecting fall well underneath the safety threshold required, we still need to be careful in considering the effect of using them in an array (well, three in an L shape) and also the impact of the focusing lens in the headset.

The relevant standard is IEC-62471. A summary of this standard is here https://smartvisionlights.com/wp-content/uploads/pdf/IEC_62471_summary.pdf

You may notice that the permissible exposure time for an except IR source on the eye is 1000 seconds (16.6minutes, pretty much exactly the length of time for which we want to restrict the use of the daily app). A Group 1 device would only allow us 100 seconds, which may still be adequate if use sparingly (pulsed, and restricted to critical moments of measurement), but it would be best to be sure our radiation levels are under the threshold of a Group 1 device.

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