Pulsed IR was used (still is probably) for beam break sensors in the alarm =
industry outdoors.=20
The only trick is getting the lens large enough so bugs and birds don't tri=
p it, but small enough that people do.
With crystal controlled modulation frequency, a detector like what's used i=
n a pseudo-doppler will give you a lot of SNR boost.

--
David VanHorn
Lead Hardware Engineer

Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO =A080301 USA
phone:=A0303-417-1345 =A0x110
email:=A0david.vanhorn@backcountryaccess.com=A0


--=20
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