Hi everyone, An auto-focus camera emits an infra-red pulse and detects the pulse reflected from the target, then it calculates the distance of that target from the camera (i.e. it can focus the target). As far as I know, all objects will emit infra-red radiation, so what is the use of the pulse emitted by the camera? Or if I put it differently, even if the camera emits an infra-red pulse, but can it receive another pulse from the target ? or even receiving pulses from another object which is not the target?