I'm a little bit confused about thermal scopes, monocular's and cameras. Maybe you can help clarify? So Wikipedia says Thermal scopes uses a "phased array" of antennas to measure temperature, then turns it into a thermogram. My question is are modern thermal imaging devices transmitting phased array radio waves from the lens, or is it a completely passive system? Also, if they are sending out phased array radio waves, can they be detected, or are they passive only?