The appealing thing with an llp setup is that it relatively easy and not that complex to do. Just mount a couple of lasers with a line lens on the plate, adjust them and the line lens and put a diffuser on the rear side of the plate.
The real danger of the use of infra red lasers is that you can’t see it when the laser light shines into your eyes. That is the reason I ordered 780 nm lasers after reading an article that they work well (http://arbi.trario.us/2008/11/02/diy-laser-multi-touch-table/ ). To be on the save side I choose for 5mw and 10 mw with 90 degrees line lenses. If the laser light reach your eyes you will see a red light so you know you have to look another way.
I have tried to find info on the internet but it is not all as clear as I hoped it would be. I think the challenge is to limit the risk of thinks going wrong with the construction of the llp setup. Lasers have to mounted/glued/integrated in a way that they can’t turn or drop down or whatever thing might happen that make the laser light shine another direction as intended. The line lens have to be attached pretty well to the lens because without the line lens the laser is magnitudes more dangerous then with line lens. (I assume)
With normal use and lasers and line lenses that stay in place and the laser light just mm above the surface you really have to give it an effort to get the laser light into your eyes. Playing around with little round dentist mirrors might do the trick. But there is always and everywhere the risk of people behaving stupid, unresponsible, dangerous, selfdestructive etc. So lets all be very carefull and use our brains and common sense.
Does anyone has a pointer to European regulation from a consumer perspective about using laser light in devices . I found info about safety precautions for people working with lasers but that is not what we are looking for I guess.