Best way to track light source?
You don't need the actual angle. You just need to know whether the laser dot is centered, and which way to turn if it is not. A simple servo algorithm will keep the detector &mdash; and anything attached to it &mdash; pointed at the laser.



When I first wrote this answer, I was assuming the existence of a lens in front of the PSD that turns the angle of arrival into dot position on the PSD. Of course, that only works if the other laser is already pointed at us. If there is no lens, then the feedback for our servo needs to come from the PSD on the other one, and the system is only useful after some other coarse positioning mechanism has both lasers already hitting both PSDs.