I did some checks by enclosing the product in a dark box with a scope probe attached and it had no effect on the signal...well maybe 1%?
Its quite hard (maybe just me) to measure presence without repeatability on the given project. The sensors output ~1V with "no presense" and 2V+ with presense. Though seeing how this changes after just a couple weeks, if I set hard thresholds for an ADC, this could change again.
Currently I have no way on startup to confirm these thresholds between "nothing" and "something" unfortunately.
I am wondering if I have over driven my IR Led at all, like perhaps it should've only been used for 20ms per second or something. Though I have kept it well within the absolute specs, even if im running continuously instead of time pulsed.