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Detecting IR beam

davenn

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Sep 5, 2009
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Tell me please...
Why can't an IR beam be detected sideways?

because a beam implies it's going in a single direction say, like a laser beam
You have to be inline with the beam to see / detect it
If you have ever experimented with lasers you will know that if there is dust/smoke etc in the air that the laser
is shining through then you will see the beam off to the side as a small amount of the light is reflected out to the sides

The same would happen with an IR beam
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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If you want to see a beam of light from off-axis you can to do something to cause scattering. (Yeah sure, there are other ways too, but they can get pretty exotic)

A simple way is to blow smoke into the space where the beam is present.
 

GerryG

Mar 6, 2018
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Most of these have a lens built into the top of the part. That focuses the IR on to the chip surface for detection. Think of it like a old bulb type flash light in reverse. You need to aim that lens at the IR source your trying to detect. Or it can be used at the focal point of a parabolic reflector for added range. sensor pointed at the reflector.
Important question! I used to work on the old F-102A plane while in the Air Force. It used an IR receiver made this way. Also nitrogen cooled for more sensitivity. 15 or more miles detection on a small airplane's engine as I recall tracking them while testing the system.


Gerry
 
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