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From: John De Armond
Subject: Re: How to use FLIR infrared camera to reduce Winter home heating 
Date: Sun, 11 Nov 2007 14:48:31 -0500
Message-ID: <>

On Sun, 11 Nov 2007 15:04:47 GMT, aemeijers <> wrote:

>> Some digital cameras and webcams already respond to IR.
>> There are various instructions around on how to convert them into IR cameras.
>> No thanks are necessary. Just send me the C-note.  :)
>> Don
>Interesting- a 'Red Green' solar eclipse/welding viewer. Too bad my toy
>digital doesn't have a protruding lens. I'll have to stare at my digital
>camera and my box of old odd fittings from my collection of 'real' (aka
>film) cameras and see if anything jumps out at me.

The IR response of a digital camera is useless for thermal imaging.  This response
maybe extends as far downward as 1.2 microns.  Thermal imaging cameras respond to
very long wave IR in the 8 to 14 micron range.  The usual imager is an array of
microbolometers that measures actual heating at each pixel and not a CCD or CMOS
device.  The better ones use cooled arrays to reduce ambient thermal noise.

The reason thermal imagers are so expensive is that glass cannot be used for lens
material, as it doesn't pass longwave radiation.  The traditional lens material is
pure germanium. Just the lens for the thermal imager I used to own cost almost $20k.
I understand that calcium fluoride has become a popular lens material and is
responsible for driving the cost down.

One other comment while I'm here.  Handheld or fixed mount IR imaging cameras are NOT
FLIR, though there is a company that as adopted the military acronym as its name.
Forward Looking InfraRed refers to the technology used on planes and helicopters. The
imaging system used in these applications is as much different from the handheld
units as a handycam is to an HiDef studio camera.

I once bought two FLIRs for one of the "B" bombers (B1 or B2, I can't recall now) at
a DMRO surplus sale.  Probably one of those sales of strategically sensitive
technology that Congress got its panties in a wad about.

This thing was over 4 ft long and probably 2 ft in diameter and required a forklift
to move.  All the optics were germanium including the massive objective lens that was
probably a foot in diameter.  It had cooled gold-plated copper AZ-EL mirrors on
frighteningly fast servo mechanisms.  The imager itself was cooled somehow -
thermoelectric or stirling, probably.  My casual testing showed that it could resolve
a half a degree F between two bodies.

The output was incredible.  No smearing or blooming like civilian imagers.  Razor
sharp crispness.  Full 30 hz frame rate.  It had several video output formats
including composite which I used to drive a B&W monitor.

I played with one of them for awhile and then sold them for mucho $$$ to a PCB
manufacturing company that used them for high speed inspection of boards during


From: John De Armond
Subject: Re: IR film, was: How to use FLIR infrared ...
Date: Sun, 11 Nov 2007 15:12:18 -0500
Message-ID: <>

On Sun, 11 Nov 2007 17:14:45 +0000 (UTC), danny burstein <> wrote:

>You might have heard the screams about five years
>ago when Sony's camcorders, when in "nightshot"
>mode, could "see through clothing". THe reality
>is that the sensors could pck up "near infra-red".
>Many materials that look "black" are really very, very,
>dark red - letting a teensy bit of visible red
>through (so small it looks blackish) but a modest
>amount of near infra-red. So these cameras could
>kind of, in some instances, maybe... look "through"
>those fabrics - if they were thin enough.

That camera and any other with the IR cut filter removed and a low pass optical
filter installed work (quite well, actually) to image through clothes for the simple
reason that many fabrics are transparent to shortwave IR.  The camera doesn't image
body heat.  It images reflected IR that passes through the cloth.  Cotton and wool
are essentially opaque.  Light synthetics like rayon are transparent.


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