Harish:
It seems like you are making this much more complicated than need be. The process....is just going to be a series of edge detects with period measurement between them. The occurance of each edge and confiirmation of a pulse width should carry your code through a sequential flow. A state machine could be coded for this. So to unfluster yourself you need to draw out a state chart of how you envision it working and then translate that to a code implementation.

By the way,,,,I would purge the idea of the black stripes on the reflectors. If the reflectors will work at all (and clearly this is something that you soon need to determine before you get too buried in the state sequence design) is to put two reflectors in one spot that are separated by a short distance and then one on the other spot. Black tapes on corner reflectors are not going to work. Are you intending to modulate the laser beam and measure the transit time of the beam to/from the reflector? If not then it is not apparent to me that you can triangulate from just two sense points. Seems to me that to get enough angles to trinagulate that you need three "corner" points to work with. If that is the case then one of the "corners" would need a set of 3 spaced reflectors.

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Have you tried the reflectors yet? Seems to me that should come next.

Michael Karas