controlling indicator lights?

[kpatil]

Hi,

When the tracker starts collecting data red lights come on at the ends of the device. So my questions are:

1. What is the purpose of those?

2. If they are just indicators that the device is tracking, then is it possible to keep them constantly off?

The intention here is that I want to collect data on-off in a session and the lights can be distracting and are giveaway that data is being collected.

I appreciate any comments/suggestions.

Best regards

[Martin]

Hi Kaustubh,

The "indicator" lights are actually infrared LEDs. They are crucial for any corneal reflection based eye tracker to work.

While it is certainly possible to use a higher wavelenght to make the LEDs "invisible" it has several downsides, one being that much more energy has to be outputted to reach comparable quality. This is because sensors typically used have reduced quantum efficiency the further up in the spectrum you go.

We have designed the system to turn them on once a client application connects to the server. To keep them constant on keep at least one application connected.

[Nathalie]

Dear Martin,

do I understand right, that 6 glints/corneal reflections appear on each eye (because of the 6 LEDs on each side of the TET)?

Thanks very much for your answer

[Martin]

Nathalie,

No, the six LEDs works as a single light source. It's similar to concepts used for LED streetlights, flashlights, car headlights, light-bulb replacements etc.
The reason there is several LEDs is that small and affordable LEDs does not generate enough light so the standard way is to combine a couple of them into an array. In principle you could use a single very high-power LED and the results would be identical (only much more expensive).

[Nathalie]

Thanks Martin for your quick answer


Annother question, is der only one camera in (the middle of) the TET filming the eyes of the user?