There are actually 3 different types of IR proximity detectors - if we rule out PIR
devices, which operate on heat pickup and not light pickup.
The one type, which is normally called "IRPD" (ala your title) works at distances of
6-18", and simply signals yes/no. These use TV IR remote style pickup devices, which
operate at 32-56 Khz, and have built-in amplifiers and bandpass filters, so they have
100X the sensitivity of your IR [u]phototransistor/diode[/u] [whichever it really is].
Yours is not an "IR/receiver", this is an IR receiver,
The second type of detector is the Sharp IR ranger that joe mentioned. That variety
actually measures distance and gives an analog output vs distance.
Then, the 3rd type of detector is just for very tiny distances, eg under 1/2" or so, and
typically used for line detection in robots. Your devices would work for that. This
explains the idea,