[GRLUG] OFF TOPIC - Speaking of Infrared...
Bob Kline
bob.kline at gmail.com
Thu Jan 28 21:51:52 EST 2010
Yup. Light is a radio wave. The issue
is whether one can form images, or
otherwise manipulate the radiation. e.g.,
1THz is about 0.03 cm, which is probably
in the microwave range, but it can be
imaged. And it can go through many
things. And since 0.03 cm is much
smaller than everyday objects, it could
spot a wiring error in a wall. Or people
doing all kinds of things in their houses.
But you won't get a unit from Cyberguys.
What you can "see" depends on technology,
which always changes, and what you can
spend.
//endjob -- IBM 360 JCL.
-- Bob
On Thu, Jan 28, 2010 at 9:31 PM, Michael Mol <mikemol at gmail.com> wrote:
> Ah, in that case, I should have directed my response to Ben. 1THz is
> actually far, far, deeper than even the far-IR stuff I work with.
> 1THz has a wavelength of a few hundred micrometers; My stuff doesn't
> even get as long as one micrometer.
>
> It borders on radio waves, which is how it gets its greater
> penetration capability.
>
> For a quick comparison:
>
> 100s of nanometers -- visible spectrum, IR
> ~300 micrometers -- This terahertz tech.
> ~3cm -- 10GHz ISM band, not used for much, but in the general vicinity
> of satellite TV.
> ~6cm -- 5GHz ISM band, commonly used in 802.11a and 802.11n.
> ~12.5cm -- 2.4GHz ISM band, commonly used in bluetooth, 802.11b,
> 802.11n, most cordless phones, newer R/C car and airplane controllers.
> ~33cm -- 900MHz ISM band, mostly used for older cordless phones, R/C
> cars and airplane controllers.
>
> Below that, you'll find your over-the-air and cable TV channels.
>
> If you're really worried about see-through-walls EM intrusion, you
> could conceivably set up a Faraday cage designed to trap the bands
> you're worried about.
>
> On Thu, Jan 28, 2010 at 9:13 PM, Bob Kline <bob.kline at gmail.com> wrote:
> > Oh, I understand. The original question
> > was what Cyberguys level gadgets could
> > do in terms of seeing bad wiring inside a
> > wall.
> > If cost is no object, one can of course
> > do more. A lot more.
> > Devices operating in the 1THz range
> > can see people inside their house.
> > Through walls. There were discussions
> > about the legal implications of all this
> > several years ago.
> > -- Bob
> >
> > On Thu, Jan 28, 2010 at 9:04 PM, Michael Mol <mikemol at gmail.com> wrote:
> >>
> >> On 1/28/2010 8:48 PM, Bob Kline wrote:
> >> > How cool was the room?
> >>
> >> Thermostat is normally 72F, but that's in another room. I'm in the room
> >> with the servers, which is usually about five higher.
> >>
> >> >
> >> > You seen to have a short sleve
> >> > shirt on, but I think I can see the
> >> > back of a chair, walls in the the
> >> > background. Is it a big room?
> >>
> >> I wear short-sleeves year-round, primarily because of the higher
> >> temperatures in the vicinity of my workstation. That was actually taken
> >> in Dec of 2007, I think. (The date is off on Flickr, but that's because
> >> the source is a BMP, and the timestamp was screwed up due to a few
> >> workstation migrations.)
> >>
> >> Room is about 750 ft^2, or about 6000ft^3.
> >>
> >> >
> >> > Jet gets to the fact that because
> >> > you stand out some the room might
> >> > be large, and-or cool
> >>
> >> I don't think you understand how far-IR temperature monitoring works.
> >> If you'd like, I can delve into a discussion of microbolometers and
> >> measurement adjustments stemming from surface emissivity, ambient
> >> temperature and ambient humidity values.
> >>
> >> There's more at work than just the wavelength of quanta, there's also
> >> intensity of emissions, considerations of atmospheric absorption and
> >> considerations of ambient temperatures reflecting off of other surfaces.
> >>
> >> What it boils down to is that in practical conditions, I can (and do,
> >> for use cases such as those that that software was written for) measure
> >> surface temperatures to within 0.01C.
> >>
> >> Don't forget I also control the palettization -- the conversion of raw
> >> temperature numbers to RGB pixels, which goes towards making differences
> >> "stand out."
> >>
> >> >
> >> > -- Bob
> >> >
> >> >
> >> > On Thu, Jan 28, 2010 at 8:18 PM, Michael Mol <mikemol at gmail.com
> >> > <mailto:mikemol at gmail.com>> wrote:
> >> >
> >> > On Thu, Jan 28, 2010 at 8:02 PM, Bob Kline <bob.kline at gmail.com
> >> > <mailto:bob.kline at gmail.com>> wrote:
> >> > > On Thu, Jan 28, 2010 at 6:03 PM, Michael Mol <
> mikemol at gmail.com
> >> > <mailto:mikemol at gmail.com>> wrote:
> >> > >>
> >> > >>
> >> > >> The chief problem with "darkvision" as it applies to passive
> >> > near-IR is
> >> > >> that there is a lot of ambient near-IR radiation that's not
> >> > related to
> >> > >> warm bodies.
> >> > >>
> >> > >> In short, your warm body radiation in the near-IR will be
> there,
> >> > but
> >> > >> largely drowned out by the ambient near-IR radiation.**
> >> > >
> >> > > The peak wavelength for a human body
> >> > > thermal spectrum is 10 microns - in the so
> >> > > called long-wave infrared range. You shine
> >> > > if you're standing out in the snow, but the
> >> > > human body is not really very hot. About
> >> > > the same as your house interior, which is
> >> > > that temperature, by design. So you don't
> >> > > stand out much.
> >> > > See http://en.wikipedia.org/wiki/Infrared
> >> > > -- Bob
> >> >
> >> >
> >> >
> http://www.flickr.com/photos/28208534@N07/3681419505/in/set-72157620862996406/
> >> >
> >> > I don't?
> >> >
> >> > What kind of image is this? i.e., how
> >> > is it corrected?
> >> >
> >> >
> >> >
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>
>
> --
> :wq
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