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Cameras seeing through clothes

  1. Nov 30, 2008 #1
  2. jcsd
  3. Nov 30, 2008 #2

    f95toli

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    Looks like it is just a very expensive IR filter for a camera. If so, yes it works to some extent and under the right lighting.
    This, however, does not mean that you can actually "see" through clothes as if they weren't there; but you will be able to see a very tinted picture showing some of the contour of what is underneath the clothes; at least if the person is wearing e.g. a thin T-shirt.
    Also, the exposure times are VERY long under ordinary light (minutes).

    IR photography is pretty popular. Just google it.

    If you really want to see through clothes you need a THz camera; these are just being introduced at some airports. But at the moment they work essentially like an x-ray machine; they are active devices (sending out THz radiation and looks at what is reflected). They are also very big (and very expensive).
     
  4. Nov 30, 2008 #3

    matthyaouw

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    I don't think this is a hoax. Probably a rip-off however. CCD sensors on digital cameras (and video cameras?) are as sensitive to near infrared as they are to light. This does not include the part of the spectrum you'd use for thermal vision.
    Ordinary digital cameras have a 'hot mirror' which is a filter that removes most of the infrared before it reaches the sensor. Without this, the thing is pretty useless for ordinary photography. You can put an IR-pass filter over the lens to shoot in IR, but unless you replace the hot mirror with clear glass, you will not be able to shoot handheld. Performance varies from camera to camera but in bright light I can manage about half a second as my shortest shutter speed. I don't know exactly how this applies to video cameras, but I would imagine you would struggle with the amount of light reaching the sensor. It'd probably be limited to daylight only as I'm pretty sure most artificial light doesn't emit much IR.

    I have head that a video designed for IR (no hot mirror presumably) was taken off the market because of its ability to see through clothes, but as far as I know this is limited to relatively few fabrics (nothing on show in any of these)

    It's a rip-off because my 52mm IR-pass filter only cost £30
     
  5. Nov 30, 2008 #4

    Evo

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  6. Nov 30, 2008 #5

    mgb_phys

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    This is just an IR bandpas filter, as the previous poster said it is only effective of you can remove the IR blocking filter in the camera. Scientific CCDs without a blocking filter and high sensitivity are quite effective at seeing through clothes - it was always a popular demonstration at open days / science fairs! It works best with thin bright cotton clothes and bright sunlight or an IR floodlight from a security CCD camera.
    It works because thin cotton cloth is fairly transparent - it jst reflects a lot of visible light that your eye is more sensitive to, if you filter this out you see the light that goes through the cloth and bounces off anything underneath.

    The machines at airports really can see through clothes, they are microwave radar with a resolution of few mm. So they can't see detail less than a mm in size - so owners of Humvees don't have to worry!
     
  7. Nov 30, 2008 #6

    f95toli

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    This is actually causing all sorts of problems. I have some colleges that are working on THz scanners for airport security and they tell me that there is a ongoing conflict between security people who want to see everything (and in the THz band you DO see everything, they have much higher spatial resolution than radar since the frequency so high) and people who are worried about personal integrity; at the moment the computers are simply "blocking out" sensitive areas before the image is shown to the operator but that obviously also means that the bad guys can hide whatever they want in those areas.

    Maybe I should add that I don't think these scanners are actually in everyday use yes, although they have been tested at some airports.
     
  8. Nov 30, 2008 #7
    yeah, the CCDs are IR sensitive. this was actually a PR nightmare for Sony a few years back with its cameras (may have been using a night mode in daylight, don't remember for sure). folks were filming people in bathing suits and putting it on the internet. it's not completely see-through, but it's detailed enough. i think they put an end to it by simply putting in a lens that was not passing IR. in any case, you can't really do this with off-the-shelf cameras anymore, it requires some kind of modification.
     
  9. Nov 30, 2008 #8
    Geez one of the example graphics is just wrong! They should call this the creepy pervert lens.
     
  10. Nov 30, 2008 #9
    I know! They censor the best part. :grumpy:
     
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