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Night vision goggles

Discussion in 'General Electronics Discussion' started by alaswad, Apr 22, 2011.

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  1. alaswad

    alaswad

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    Apr 21, 2011
    Hello everyone,

    I have a question.

    I know that night vision goggles rely on light amplification or thermal imaging techniques to have an image in darkness. I have searched the web and I can't seem to find goggles that do the same function but using SONAR technology, or imitating the way bats see.

    Is there a reason this kind of goggles don't exist?

    Cheers
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    A good stab at an answer to that would be the problem of low resolution of objects at ultra sonics compared to infrared light.

    the higher you go in frequency, the better the resolution of smaller objects/finer details

    Dave
     
    Last edited: Apr 24, 2011
  3. alaswad

    alaswad

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    Apr 21, 2011
    But how come? I mean I thought that if we could mimic bats we would have an excellent output no? And we already use SONARs in boats and sonography in medicine, couldn't these technologies be used to do the same?

    I checked, bats emit soundwaves between 40kHz and 120kHz. Sonograms do it at 2MhZ+ and as you said the higher the frequency the better resolution but they say bats are very good hunters..
     
  4. davenn

    davenn Moderator

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    yes we use sonography in medicine but its resolution is rather (very) poor compared to MRI and X-rays, and it only penetrates the body a short distance.
    when was the last time you looked at a boat sonar display ?
    once again its resolution if pretty poor

    yes they are good, but their "sonar" still gives them a very poor "view" of their surroundings compared to our visible light vision or even IR vision with goggles
    Sound has a very limited distance, I have never seen anything written but I would be suprised if they had any useable vision over ~ 50 -100 metres compare that to how far you can see into the distance !! :)
    Hi frequency audio gets attenuated very quickly

    2MHz freq is extremely low compared to the freq of IR,visible light or X-rays

    Dave
     
  5. davenn

    davenn Moderator

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    This is getting away from electronics but hopefully it will be found interesting in the context of the original post

    Here's another good comparison....

    In astronomy we have 2 common methods of viewing the objects out in space.
    Radio and light.
    for a start lets just look at light InfraRed through Visible to Ultra Violet and the huge difference that makes in what we see of an object....

    pic 1 ...see along the top the views in UV, Vis and PR how different they are.

    in pic 2 and 3 are radio and optical views of the Milky Way ( I will assume you know what that is ??)
    look at the difference in resolution in radio freqs we cant even pick out individual stars

    cheers
    Dave
     

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    Last edited: Apr 25, 2011
  6. Wintermut3

    Wintermut3

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    Apr 25, 2011
    I would like to add that water is a VERY efficient conductor of vibrations, that makes sound much much more reliable and viable underwater.

    On the surface there are more efficient ways.

    Also if I understand correctly the best resolution you can get is equal to the peak-to-peak distance of the wave that is providing the imaging. For visual light that's in the nanometer range, for radar it can go down to the millimeter range, for sound it would be substantially more fuzzy.
     
  7. Resqueline

    Resqueline

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    Jul 31, 2009
    There are a lot of technologies/gadgets that would not have seen the light of day if not for strategic purposes, night vision & IR cameras certainly being among them.
    Surely an ultrasonic camera could be made, and we're already seeing an increasing number of cars cropping up with distance sensors with increasing angular resolutions.
    There have also been experiments with acoustic distance/direction devices for the blind, but I don't know how far it has been developed.
    There are a number of (strategic) disadvantages compared to optical means though, and poor resolution is only one of them.:
    Because of poor acoustic coupling between the element and the air, the elements needs to be large, and thus an array would get quite bulky with increased resolution.
    Because of the same poor coupling you need to spend quite a bit of energy, and still you'll get a very limited range.
    A sweeping detector/array would introduce mechanical noise & vibrations and also a directional error due to the limited travelling speed of sound.
    For strategic purposes (both of) the sounds emitted would be all too easy to detect and pinpoint by the enemy (even at a distance), making the observer a sitting duck.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I think a point that should be made with reference to the original question is: Bats have quite good eyesight.
     
  9. davenn

    davenn Moderator

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    Sep 5, 2009
    indeed, not all Bats are blind

    the old saying "blind as a bat" is a bit misleading

    Dave
     
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