For anyone interested, I will show the auxiliary lenses that I use with both my Ex Fire service cameras and the FLIR PM series.
The lenses are as follows:
1. Inframetrics single element Germanium Meniscus 6" Close-up lens 58mm.
2. Chinese GaAs CO2 Laser Bi-Convex 4" focus point lens 19mm in lens holder.
3. Chinese ZnSe CO2 Laser Bi-Convex 4" focus point lens 19mm in lens holder.
4. Commercial Germanium Lens protector, high transmittance coated 35mm.
The Inframetrics lens is interesting in that the concave side faces the target and the convex side faces the TIC primary lens. This lens offers excellent transmittance, anti-reflective coating and good depth of field. If you see one cheap, buy it !
This isn't a cheap one .......
http://www.ebay.com/itm/FLIR-Systems-100-m-Close-Up-Lens-LW-34-80-/121185050471?pt=LH_DefaultDomain_0&hash=item1c37311f67Neither is this........
http://www.ebay.com/itm/FLIR-Systems-MACRO-LENS-50-MICRON-P-N-1700-500-/300951292680?pt=Camera_Lenses&hash=item4612184b08The two Chinese Bi-Convex lenses are 19mm diameter and are symetrical. They fit perfectly into the 19mm filter/lens holders that were used on older compact cameras of the 1970's. Good Camera shops still have some old stock of these types of holders. The price of the holders is around $5 each.
The weird 'lens' with the plastic shell and red 'hood' is in fact a lens protector made from a very thin piece of Germanium for low through loss. The red fitment is used only to insert the protector into the lens aperture of the TIC for which it was designed. These lens protectors are expensive (approx. $250) but protect the even more valuable primary lens in the TIC. I will be mounting the protector on a filter step down ring for mounting on the TIC's.
A very cheap alternative to the expensive Germanium lens protector may be constructed using a filter holder and a sheet of 25 micron Polyolefin Shrink Wrap plastic. Its not perfect but is effectively transparent at thermal wavelengths. FLIR offer such cheap protectors as disposable alternatives to the more expensive options. I bought a 20m x 45cm roll of the Polyolefin Shrink Wrap for $7.50
http://www.ebay.co.uk/itm/350800488552?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649That should last a few years. You can also make temporary external weather proof housings using the shrink wrap as the face plate. Great for wildlife observation which is what I intend to do with my cameras.
For anyone wondering why Germanium lenses are so expensive, they have to be grown as a single crystal of Germanium. The crystal is then cut and ground to the same optical standards as instrument grade vision wavelength lenses. The lens is then coated with a special anti-reflective coating (at thermal wavelengths) to improve its performance. Think carefully before buying a Germanium lens with damage or coating loss. This will degrade performance seriously. Sharp impact can cause a Germanium lens to suffer micro fractures within its single crystal structure....very bad news ! In summary, thermal camera lenses are a very specialist product that is made to very exacting standards. The price increases exponentially with diameter which is why the cheaper cameras have small lenses and so are less sensitive. \take a look at my PM695 primary lens ....its almost 60mm in diameter and the internal focussing lens is 50mm diameter
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= Very expensive