<h1>DIY Thermal Lenses</h1>

The problem with glass is that it filters out most of the thermal energy we need to detect people with FLIR devices.

here we can see normal glass preventing wavelengths above 2.7um (2700 nm), which is no good. Were interested in energy much further along, somewhere between 8um and 20um.

There are basically 2 solutions.

A.) Make lenses from exotic materials like germanium (talking $800 min), Silicon, salt or Poly-IR. Or,

B.) Don't use lenses.

Whereas most thermal devices use lenses, we can use mirrors. Mirrors are in many ways better than lenses.



Mirrors are generally lighter and cheaper to produce, and first layer metal mirrors maintain very high reflection efficiencies throughout the electromagnetic spectrum.

I am in the process of making a Parabolic mirror for a BHD with a combined budget of around $15, lens and all.

By covering a glass sphere in Papier-mâché. you can get a pretty decent parabola, which can be chosen for size, gain and focal length.

When mine has dried it will be lined it with thermal blanket material (Aluminized PET) from Dollar Mart and lacquered to ensure environmental stability.

Ill upload make shots when it's all fully tried and tested (read;=: a month)

Well, here you can see the mold, and the thermal blanket material. You can make out the papier mache layer just about.