This tape is whats called retroreflective. It has very small three corner cubes
in it that reflect light directly back to the sender. Just like the reflectors
the astronaughts left on the Moon. It would not take much power in a well focused
beam to be able to detect it comming back even in bright sunlight. Have you ever
been driving down the highway and see the roadsigns light up from the light
reflecting off your windshield? It looks very bright but the reflected light
from a windshield is not nearly as bright as the sunlight.
I have even noticed the reflected light from signs caused by turining on
my headlamps during the day. (I know that sounds kind of strange but I
do automotive lighting and optics for a living and have done some unusual
things testing various lighting systems)
I am going to start running some tests to see how much reflector area is needed
and what kind of light projector, sensors and optics would work best. I will
keep everyone informed of my progress.