Heated Germanium Window Assembly
Heated Germanium Window Assembly
(OP)
I'm trying to figure out how to specify a direct heated Germanium sensor window for rugged LWIR sensor. I can't use a thin-film/kapton heater placed around the perimeter of the clear aperture. I've read it is possible to heat the Ge window directly but there is a dearth of data online about this solution. Only one supplier claims the capability, but no data posted online about it.
Ideally, I would like to have bus bars at the top and bottom on the inside surface of the rectangular window and contacts for a thermistor. But, since the Ge is the "element", does the electrical connector need to be made on the edge of the window?
And direction to a supplier or example of a heated Ge window will be gratefully accepted.
JMCAero





RE: Heated Germanium Window Assembly
The second issue is how much power you need to apply. For a typical anti-icing application in moderate airspeeds, you need something on the order of 2.5 W/in^2 across the window to get effective results. No matter how uniformly you apply the power, there will still be a slight bow, so anything that requires precision boresighting would need to operated with the heater turned off.
Several alternatives to direct heating exist. Battelle and several other companies make a photolithographic metal heater grid that's deposited on the surface. This allows the use of non-conductive windows. Ditto, Indium Tin Oxide (ITO), which is a surface resistive element. Both of these will tend ot reduce transmission through the assembly.
Note that Ge will lose its higher wavelength transmission when heated.
TTFN
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