unknown thermal lens....

[Lambda]

Hello, 

I own the following thermal lens:



I was speaking shortly about it in this thread:
https://www.eevblog.com/forum/thermal-imaging/my-first-little-diy-thermal-camera-project/

But i would like to especially know more about this lens:
The only things i know are that:

- the diameter of this Germanium (i guess) lens is (optical diameter) 40mm,
- the focal length is around 40mm,
- the front surface is convex, and the rear/back surface is flat,
- the apparent average thickness of the lens by itself (without knowing if it is a single element or a 2/3... elements) is around 8mm,
- the body (around 90mm total length) is in a kind of ceramic, brown/cream outside, black mat inside, with a connecting rear metallic thread (kind of stainless steel)

No marks, brand,...
no focusing mechanism,

Therefore, it would be great to know more about it...

In advance, as usual, thank you a lot for sharing your knowledge and culture here.

Best regards.

Stéphane

[IR_Geek]

My first gut instinct says it's from DIOP due to that off brownish color.  Almost looks like the front is missing an optic - the small valley on the outer edge and what appears to be a push pin or lock pin.

Sorry I couldn't be more help.

[Fraser]

It is the correct colour for an Ex Military optic painted in desert sand camoflauge. I have a couple of Military cameras that are painted that colour.

I agree that the front lip on the lens suggests that it mounts into some orifice that uses a locking pin, clamp or bolt. It could be the optics out of a military vehicle thermal camera installation. If it is military and that is Desert Sand camouflage, it was deployed outside of the vehicle or surveillance station. There is little need of canouflauge inside the vehicle  Tanks tend to be a lighter colour interior as well.

If this is a complete optical system that is not a long range lens, I would expect it to contain at least two lens elements, one at the front, one at the rear. It could be that the rear lens element was part of the detector system to which this lens was attached.

Military lenses are often anonymous with no makers name as a matter of policy. Your only chance of identifying the system it came from would be if someone recognises it or you discover it in a picture of military thermal imaging equipment.

Fraser

[Fraser]

A total off the wall comment from me regarding the appearance of the lens housing...... I have seen similar looking lens housings used on professional microscopes in the visible light range. The grooved end is locked into the microscope ‘camera’ port using a locking screw or screws. There are such things as IR/Thermal microscopes so this could possibly be a sand coloured industrial thermal microscope camera adapter tube. 

Fraser

[Lambda]

IR_Geek, Fraser, thank you a lot for your input! 

I have now a good track to investigate more. It seems that it converges on somehow a military origin....

What i can add it that when i use this lens with my A10 Core, for observing a scenary/landscape, i obtain a quite nice image, but less bright/with less contrast than with the genuine ZnSe lens 8mm/F1.2.

Regards.

Stéphane