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Detecting IR beam

Discussion in 'LEDs and Optoelectronics' started by roughshawd, Jul 15, 2020.

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  1. roughshawd

    roughshawd

    18
    1
    Jul 13, 2020
    Tell me please...
    Why can't an IR beam be detected sideways?
     
  2. davenn

    davenn Moderator

    13,713
    1,911
    Sep 5, 2009
    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
     
    narkeleptk likes this.
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    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.
     
  4. GerryG

    GerryG

    2
    0
    Mar 6, 2018
    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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