Spectral responses

I don't have detailed information, but on the anti tank missiles that use the thermal image of the jet to direct the missile to target, the lens material is a germanium arsenic construction, if I remember correctly.

This was for long wavelength infrared transmission.

John.

Low OH silica (quartz), or sapphire, would also be good alternatives to plastic. They would also be more durable. Certainly be less expensize that GeA crystal.

The website for the Rochester Cluster has a listing for a company that makes plastic lenses. That would be a good start if you need to stay withe plastic to keep things on the cheap.