Laser-Only Activated Sensor

Thank you all so much. It looks like my project is not dead.

I will try the filter approach first, both wavelength-limited and color filtered.

It seems a more refined process may be the frequency modulation. At that point, the

laser could be of many colors and intensities but have a singe modulation frequency.

If moving in that direction seems most prudent, how might I proceed best with my 650nm

test laser?

Thanks....