FreeTrack Forum

Hi to All,

    I know that some of you will consider this post a little bit too exaggerated or that I'm getting concerned about nonsense just from reading the name of the topic, but here goes my question:

Is there a possibility for an eye damage to occur from IR LED radiation originating from some of the model points which are in the peripheral viewing field and near to the eye ?

   Namely, I have just finished constructing my 3 point clip model with the default dimensions  found in FreeTrack 2.2  a few days ago, which puts the bottom LED located pretty near to the head and in the peripheral vision field of the left eye. The LED's used are Siemens LD274 filed down and operating at 1.4V and around 150mA which dissipates around 210mW per LED with a spectral characteristic of 940nm +- 50nm.  My mistake is that I used too weak resistors for the construction and the LED's are indeed being registered very bright on the web cam. What really concerns me is the fact that I woke up the next morning after testing my Free Track with a lot of broken capillaries in my left eye   , although it was probably due to a lot of staring in the monitor during the night  being anxious to try out  FreeTrack   . By the way the first impressions were really great   , except  that now I'm concerned if I need to visit an ophthalmologist   . In any case I will now construct a smaller model which will be out of the viewing field and replace the resistors with larger ones to operate the LED's at a lower voltage of 1.3V and 100mA. Just wanted to also hear your opinion about the safety of using IR LED's so near to the eyes and general safety concerns about the hazard of IR radiation, since nobody has so far discussed this issue on the forum. Thanks a lot in advance.

Best Regards,
Loaded Dice

IR light is less dangerous than visible light, because its frequency is lower, _but_ the problem is that you don't see it so you don't protect your eye against it.

So it makes sense that your eye got tired because of IR (I am no expert, I just thinks it is not absurd).

I found a discussion in french here: http://www.docmirror.net/fr/linux/howto/hardware/Infrared-HOWTO/Infrared-HOWTO-14.html where they say it should not be a problem, but  they saw in the Omnibook specification to not look straight on the IRDA leds.

Anyway, the way to go with Freetrack is to remove the IR filter of your Webcam and to spend at most 25 mA in each of your diodes.

this is an interesting and not "easy to answer" topic. i did some research on it because of a project at my university. as haltux mentioned, because IR light is not visible to our eyes, the eyes won't "warn" it's human owner that they are getting too much or too intense light.

it's also right that IR light has less "energy" than visible light - but there is another problem. because of it's frequency, IR light transmits more "heat" than visible light. the human eye is very sensitive to that, as the inner eye is made nearly completely of a fluid. fluids that get warm increase their volume - not good for the eye as i was told by opticians.

there are very few good articles/studies about that (diffuse IR light <-> human eye), the most stuff i found is about IR lasers, which is a totally different story than with diffuse lighting as with leds.

to be safe, i just used 2 small pieces of cardboard to block the IR light of the leds of my "head tracking cap" from my eyes. just make sure you cant "see" the leds, than you do not have to be afraid to damage your eyes.

ps:
sorry for my english, i'm from germany.

Thanks a lot  for the  answer guys    .  My eye got back to normal condition during the next day so I suppose there is no permanent damage here for sure. I also did some exploration on this topic afterward, and I think that there is nothing to be worried about, especially that the LEDs used in Free Track are wide angle so the power transmitted per square unit is not focused and thus too small to cause any eye damage. Anyway, I would recommend some safety precautions to be taken, like limiting the transmitted power and if possible keeping the LED's in the model out of your field of vision. I also followed a similar approach as @Spliff and covered the sides of the LED's with black electrical tape not to transmit light to the sides since only the front is needed to be seen for tracking. I would also like to use this occasion to express my big thanks and respect to the developers of this wonderful piece of software, after some tweaking and setting up it works pretty good  

I really don't see how these little LEDs could have any adverse effects to the health of your eyes anyways. I seriously wouldn't stress it.

I doubt it would have any adverse effects, still I rolled a small amount of electrical tape around the back end of my peripheral LED's.
This tape is actually recommended in some build instructions as it cuts down on bounced light and helps freetrack.
Better safe and slightly paranoid than sore.