2
$\begingroup$

enter image description here

I saw this cod black ops 4 cod is based on realistic gameplay, so i am curious if thermal cameras really can do that? i think this may be a possibility if the sensors are highly sensitive and can detect lower intensities.

$\endgroup$
1
  • $\begingroup$ Check out "Terahertz Imaging". $\endgroup$
    – JEB
    Jun 1, 2018 at 15:06

2 Answers 2

3
$\begingroup$

Thermal radiation (the wavelengths emitted by human-temperature objects = 10 micrometers; hotter objects (barrels of recently fired firearms?) emit shorter wavelengths, eventually so short (smaller than 800 nanometers = 0.8 micrometers) as to be visible by the naked eye (you can see something glow)).

Different Wavelengths pass though materials differently. It is not safe to say 'the longer the wavelength the better it passes through', it actually is a very complex function that governs this. Look at some transmittance graphs to get a feel for it. Even air sometimes absorbs wavelengths completely, i.e. air is opaque for that wavelength. enter image description here Visible light is blocked by fog, some longer wavelengths are not, which is an additional bonus for night-vision cameras. Some plastics are impermeable by visible light, but permeable for light just a tiny bit more long-wave, this was the reason for the infamous Sony-camera-night-vision capability of filming 'through' fabric.

For very thin walls and very capable cameras it might also be possible to detect the heating of the piece of wall that a human is leaning on, from the outside (from the inside even a cheap thermal camera like the iPhone addons can detect that warm spot even minutes after the human moved away). But stone or wooden walls will generally not be translucent in the 10 micrometer wavelenghts, at least not translucent enough to make that clear a picture as you posted - think of slightly translucent materials as a glazed window - you'll be able to precisely locate a flame on the other side, but only if it is very near to the glass)

But every object not only emits the peak wavelength for it's temperature, but also all the wavelengths longer than that - and more of that than an object whose peak wavelength is that longer wavelength. Think about a white-glowing metal - it emits at peak wavelength greenish-yellow, but also at red (both combine for 'white')- and it emits more red than a red-glowing metal (which is quite dull for that reason). So humans also emit longer wavelengths than 10 micrometer, and they emit more of it than their (colder = longer peak wavelength) surroundings. So if you find any wavenlength above 10 micrometers that walls are transparent for, you are all set.

That wavelenght is at the outer limit of the waves called 'light' and at the beginning of the waves called 'microwaves' - this part of the spectrum is called Terahertz radiation. It is detectable, walls are transparent to it, and the detector to fit on a man-portable weapon is buyable.

But Terahertz radiation passes through most things, and it is not a simple feat to design optics for it, for that reason and for the reason that everything that is not supercooled does itself radiate THz radiation... think of the problem as wanting to build a camera from red-glowing glass lenses... So you can either ditch the lenses and have a sort of crappy pinhole camera, or you can supercool your optics, which is a drag.

So answer: Possible to image humans though walls? Yes. The picture you posted? No. (Picture would not be as sharp, other sources of warmth (wall-plugs, warm water lines, etc) would also show up, and the goggles/scope would be quite bulky)

$\endgroup$
3
  • $\begingroup$ if detect only the band emitted by human body,will it be possible to get a better image $\endgroup$
    – Iamme
    Jun 1, 2018 at 15:24
  • $\begingroup$ if we detect only band emitted by human body,will it be possible to get a better image $\endgroup$
    – Iamme
    Jun 2, 2018 at 4:54
  • $\begingroup$ I take that as a question? Answer: No and Yes. There is no band exclusively emitted by the human body. Any thermal radiation wavelenght that humans emit is also emitted by everything warmer than a human. What you can do, and what is done, is to make a picture for wavelenghts peak-emitted by 50°C objects (and this not emitted by 37°C objects), and one for wavelengths peak-emitted by 37°C (and co-emitted by 50°C objects), and then substract one from the other. Also, other forms of post-processing will improve the image, but also introduce the possibility for sneaky countermeasures... $\endgroup$
    – bukwyrm
    Jun 2, 2018 at 8:33
0
$\begingroup$

If the wall is not blocked by any conductive materials or materials that emmit a lot of thermal radiation or such materials that have high magnetic permeability. It helps if the wall is colder than the outside.

To make an example. If you put your hand in a black plastic bag, you can see your hand with thermal camera as if there was no bag present.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.