Want to see a ~$5000 close-up lens ? Here you go :)

[Fraser]

As some readers may know, it makes me smile when I read peoples posts on this forum complaining about the high price of thermal cameras these days and how they should be much cheaper. This has even been said of the diminutive and cheap FLIR One Gen 2 cameras at $250. Why do I feel amused at these postings ? Well I have spent almost 26 years working with this technology and I have seen how far we have come, and how much the price of hardware has dropped. It has never been cheaper to own a decent thermal imaging camera.

I have a very large soft spot for the FLIR PM series industrial thermal cameras. Maybe that stems from spending 3 long months reverse engineering the PM570  I own several PM series cameras and I am always on the look out for accessories on eBay and other sales outlets. Sometimes I get lucky, but those occasions are rare indeed. This is not a common technology when compared to consumer products.

I already own the Wide angle 0.45X and Telephoto 2X supplementary lenses for my PM series cameras. I have been using a lovely Inframetrics close-up lens attached to the front of my PM series cameras via a simple adapter. The inframetrics 6" FL lens is made using a top quality Germanium lens element, and it cost a small fortune new. I also own the 12" FL version but this is less useful. I did not expect to find the correct AGEMA/FLIR close up lens any time soon.

Well the Gods smiled upon me and I literally stumbled upon an 'eBay local' listing in Germany. It was a German language site that is basically set up for selling items locally, not internationally. I used Google Translate to work out how to sign up for the site and became a member. After some relatively simple discussions with the seller, the lens was winging its way to me in the UK. The seller had been asking for 250 Euro's but we agreed on 200 Euros in the end.

Now 200 Euro's may sound like a lot of money for a 'simple' close-up lens, but these things are very rare indeed and far superior to say a simple ZnSe lens designed for a CO2 laser. This lens is around 60mm in diameter for a start. They were hand finished and originally cost around $5000 ! Yes Five Thousand Dollars, circa 1997. Now that is a lot of dosh 

The close-up lens has the correct mount to not only mate with my PM series cameras, but also my recently acquired FLIR A40 camera. It contains the lens type coding in the ring that tells the camera which supplementary lens is fitted. Calibration offsets are then applied.

So there you have the back story. You will still pay around $5000 for such a lens from FLIR's professional camera range. They are expensive to manufacture. No cheap moulded Chalcogenide Glass materials used in these lenses !

So before any one complains about the cost of thermal imaging equipment, see how far we have already come in cost reduction, and be grateful 

Picture time..... Imagine paying $5000 and receiving just this 'simple' looking lens in the post .... ouch !

Fraser

[Fraser]

Just a picture of the PM series PM675 camera and its large robust supplementary lens mount

Fraser

[RoGeorge]

Nice finding. Post some nice IR pics, please!
 

In optical photography, a normal lens mounted in reverse (with an adapter ring) makes a very good macro lens, I wonder if this is possible to do for IR cameras too.

[Chanc3]

Can you post pictures of the images take with all of the different lenses? Would be good to see a comparison!

[Fraser]

Yes, a complete thermal camera lens may often be reversed to create a macro lens. Using the same approach for a supplementary lens requires the camera lens and supplementary lens to have the same FOV and diameter.

I will one day get around to producing pictures from my cameras for upload. There are a lot of demands on my time though, and such is not a five minute job. I will see what can be done though.

Fraser

[cdev]

What materials can be used and what not?

Is the need for exotic materials the only reason they are so expensive?

With digital cameras some optics work okay for IR, some don't.

The focus is always different.

[Fraser]

Germanium is the most commonly used lens material as its properties make it excellent for the role. A Germanium lens is made from a slice taken from a mono crystal. Germanium is very expensive to grow and to turn into a lens

There are other materials that have decent transmission at thermal wavelengths and many are cheaper than Germanium. Examples are Silicon (for SW IR). ZnSe, ZnS, Galium Arsenide (GaAs) and the very popular Chalcogenide moulded IR glass. The last material is now common in most budget thermal cameras due to the lower cost of production.

Materials that will not transmit thermal wavelengths are many. Optical and NIR glass being just two.

There is plenty about SWIR, MWIR and LWIR lens materials on the internet.

Fraser

[alm]

Yes, a complete thermal camera lens may often be reversed to create a macro lens. Using the same approach for a supplementary lens requires the camera lens and supplementary lens to have the same FOV and diameter.

Reversing a close-up lens only makes sense if this improves the match between the main lens and the close-up lens. Generally this is only the case if you use a close-up lens together with a dedicated macro lens. Close-up lenses are generally designed for an object distance that is larger than the subject distance. Combining them with a true macro lens can reverse this situation. Otherwise I would not expect much if any improvement from reversing the close-up lens.

[Fraser]

Some confusion about my message has occurred here.

My comments refer to removing a thermal cameras normal lens block and reversing it, as done with SLR cameras. The Close-up lens is not involved.

My second case involving a matched secondary lens block reversed in front of the cameras lens block is a well known way to effectively produce a thermal microscope capability.

That is to say.... if your microbolometer has 25um pixels with a 24 degree FOV 15mm focal distance lens in front of it.... and you add another identical 24 degree 15mm focal distance lens in front of that lens, but reversed..... you will have the ability to resolve 25um objects at a focal distance of 15mm in front of the lens.

Reversing a Single element close up lens is not something I would see as a worth while proposition.

Fraser