I have bought a IR rear camera 
(see
http://cgi.ebay.fr/CAMERA-DE-RECUL-COULEUR-MIRROIR-ET-VISION-DE-NUIT-IR_W0QQitemZ130043199531QQihZ003QQcategoryZ113057QQrdZ1QQcmdZViewItem)
and I have monted it below the rear window of my car 
(see pictures at
the bottom of this page :
http://www.forum-peugeot.com/Forum/demonter-hayon-arriere-807-pour-cam-recul-27696-0.html).
The problem is that, at night, IR light form the camera is reflected
by the heating resistance that is inside the rear windows (see black
lines on the rear windows :
http://www.hiboox.com/image.php?img=cdac7886.jpg), so the cam image is
saturated by this reflected light and I don't see anything on my LCD
screen.
I havec tried to paint the resistance in black colour, but IR light is
reflected by back colour !
So my question is : what can I do to avoid IR light beeing reflected
by the heating resistance of my rear windows. Can I found on web
merchant or on department stores some painting that absorbs IR light ?
Is there another solution (I don't want to remove the eating
resistance of my car) ?

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Clarification of Question by phkoech-ga on 03 Nov 2006 08:56 PST

Thanks for your help !
Unfortunately, I cannot mount it outside the car because of water,
risk of being stolen, and because it?s to complicated to mount on the
rear door. Anyway, this position is the best position I found to see
the whole area back to my car.
The camera is very close to the windows (it doesn?t appear on the
picture because of the angle of view), so it cannot be closer.
I cannot chose the place of the camera because it is supposed to be
fixed to the rear door of my car (against the plastic) and furthermore
it should not mask the rear window visibility.

As qed explained in the comment, painting the warm surface with absorbent material
will not help. You would need to  have a window ( small circle cut into a rear 
window) covered with a material which is transparent to IR

You need to decide 'what is IR and what is transparent) as indicated in this
Answer from a different service
http://sg.answers.yahoo.com/question/index?qid=20061029200658AAWl7IU

Ordinary glass is not transparent to IR.

There are companies which serve that industry
http://www.okamoto-glass.co.jp/eng/rd/rd0b.html

Industry is mostly IR spectroscopy:
http://www.okamoto-glass.co.jp/eng/rd/rd0b.html
http://test-equipment.globalspec.com/Industrial-Directory/infrared_spectroscopy
SEARCH TERMs: IR spectroscopy, tutorial
              IR absorption spectrum

 You should ignore the 'complicated part' - the position of peaks
(used to identify the chemical compounds) and focuse on the techniques.

Sepending on how serious you are, you should do more or less reading:

on the topics of IR photography

://www.google.com/search?num=20&hs=TOb&hl=en&lr=lang_en&client=opera&rls=en&q=IR+photography&btnG=Search

Hedgie

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Request for Answer Clarification by phkoech-ga on 05 Nov 2006 01:15 PST

Hedgie,
Thanks for your response. 
In fact, my rear window is transparent to IR, so there is no problem about that.
The problem is that the rear-window heaters are not transparent to IR
(even if they are not in use). By night vision, the heaters reflect
the IR light and then my camera is over-exposed, so I cannot see
outside.
So my question is: "can I put on the heaters a substance that absorbs
IR light" so that they will appear dark on my cam instead of bright.
In the links you gave me about "IR photography", they say that water
and blue sky absorb IR light, but it is not very easy to apply in my
case. Maybe some photographic filters can do this job very well, but I
cannot find a reference on the link you game me.
Thanks for your help.
Phil.

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Clarification of Answer by hedgie-ga on 08 Nov 2006 00:08 PST

phkoech-ga

   I do understand your question. You say that your rear window is transparent
to the particular frequency of IR your camera is using, and that is possible.

Neverthless, your attempted solution, namely to cover the heaters with
'absorbing paint' seems to be based on an analogy with visible light,
which
does not apply to IR:

The energy (of light) has to go somewhere. In most cases, it is converted to
heat - and radiated as IR. Meaning, even if you had the perfect absorber on
the rear windows, it would get warm and radiate the same amount of IR you
started with. It would not radiate in visible range (which is why absorbers
work in visible and UV range). They do not work in IR.

So, my advice is : Stop searching for an absorbing paint. It would not solve
your problem

It is possible (in principle) to find some phosporescent paint, which would
radiate in some specific frequency band (which your camera does not see),
but it surely seems more simple to cut a small circle into the rear
window and cover it with cool glass, transparent to IR.

So answer to your question:

 "can I put on the heaters a substance that absorbs
IR light" so that they will appear dark on my cam instead of bright.."

is NO.

 You can find absorbing substance, and put it on the heaters,
 but it will not make those areas appear dark to your camera.

What is dark in visible is not dark in IR.

As a freebee, attached to the answer is this: There are other ways of achieving
your goal. e.g., switching the heaters off and keeping whole rear window cool.

Hedgie

Does this help?

http://en.wikipedia.org/wiki/Radar_absorbent_material

U will have to mount the camera outside the car for best effects

Hello,

   Are the rear-window heaters in use when the problem occurs? If the
resistance-wires have electric current running through them, then
they'll emit large amounts of their own IR light, completely
overwhelming the camera. Painting over the heater wires can't solve
this sort of problem, because the paint itself will absorb the heat
and emit IR. It needs to be mounted where there'll be no overwhelming
sources of heat. The camera also has a very strict range of operating
temperatures, and wherever it's mounted it must also be able to remain
within that temperature range.

   I see in your picture that the camera is mounted several
centimeters away from the glass, which allows the wires to be within
the camera's wide-angle field of view. You could try rigging up
something to hold the camera so that it's only one or two centimeters
from the glass, exactly half way between two of the heater-wires. That
way the wires may be entirely out of view. I see that at near the
bottom of the window there's a region in which the last two wires are
rather far apart. You could mount the camera to look directly through
those two.

Thanks for your help !
Unfortunately, I cannot mount it outside the car because of water,
risk of being stolen, and because it?s to complicated to mount on the
rear door. Anyway, this position is the best position I found to see
the whole area back to my car.
The camera is very close to the windows (it doesn?t appear on the
picture because of the angle of view), so it cannot be closer.
I cannot chose the place of the camera because it is supposed to be
fixed to the rear door of my car (against the plastic) and furthermore
it should not mask the rear window visibility.

From what I understand from these two sites, IR imaging through glass
is a real problem:
http://www.kenrockwell.com/tech/ir.htm
http://coolcosmos.ipac.caltech.edu/cosmic_kids/learn_ir/index.html

You have to scroll down a ways to find the relevant texts.

I expect that you have a problem with the warmth of the the glass
relative to the outside air at night  - even without the defroster
being on -  plus the fact that the glass reflects the heat image of
anything outside the car.

What wavelentgth IR is your camera?  Without this knowledge an answe
is not possible.

The problem, as the others have commented is that the infrared light
presumably tends to warm up the element, and warm things emit...
infrared light. You could try painting over it with white paint, that
would tend to reflect it away, but I'm not sure that that will work,
it will tend to shine back into the camera.

More promisingly, you could try the opposite- adding a mirror over the
top of the heating element, angled so that it doesn't shine into the
camera. Silver foil might be a good choice, but you need to insulate
it from the elements. Still, it would be fiddly to arrange.

Instead of making the heaters to absorb the infrared light you could
make the infrared light to reflect in other direction, instead of back
to the camera. I think a mirror reflects infrared light the same way
that visible light, so masking the heater with a tiny mirror (or maybe
aluminium foil) that reflects the IR light downards may work.

(Or you could remove (cut) the heater.)