Dear all,
is it right, that there is allways a heated victim, when there is a letter on the wall?
Or is the letter solitary on the wall?
With other words, have I to dedect the letters only with a optical sensor or is it possible to search the heated points and then searching for a letter near by?
Another question: Is the letter in the middle of the tile? (In the length, not in the high) Or is it possible that it is fixed in a corner?
Thank You
Andreas
Dear IGSKaufungen,
Not sure I understood your question, but will try to answer below. If you have any more question please ask again! 
The visual victims does not need to be close to any heated victims. The visual victims can be located anywhere.
You have to detect the visual victims with something that measure light / images. A camera or a bunch of light sensors would make it?
The letter does not need to be in the middle. But will probably be. But just as heated victims they can be in different places and even in the corners.
// Fredrik Löfgren