Author Topic: Interesting lens .... FLIR 4mm / F1.3 / 90 Degree FOV - latest acquisition :)  (Read 690 times)

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Offline Fraser

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The Backstory....

I wanted a wide angle supplementary lens for my Exx series camera but they cost a small fortune from FLIR. Such lenses are not that common on eBay so when they do appear, they sell for decent money. I was considering using an adapter to mount my PM series 0.45x supplementary lens on the Exx lens mount but have yet to progress with that project.

The purchase....

A few days ago I came across an interesting FLIR wide angle lens on eBay. It is an unusual shape so I immediately recognised it as the 90 Degree FOV lens I had seen in accessory catalogues. It is quite large and unusual in shape for good reason. The lens provides a wide field of view and can focus down to 40mm. It is useable for normal target imaging at close quarters, distance work and IR viewport use to image the interior of electrical cabinets.

The lens specification is as follows:

Pt No. T197306 : 4mm F1.3 90 Degree FOV supplementary lens with viewport capability down to 0.5" and near focus capability of 40mm. Distortion is 5% (Eeeek!)

The lens is also listed as Pt No. T197411 (FLIR often use different part numbers for the same item over the life of the product)

https://www.infraredcamerawarehouse.com/content/FLIR%20Datasheets/FLIR%20Lens%20%2890d%204mm%29%20%28T197411%29.pdf

Compatibility......

The lens is intended for use with the A /SC3xx / Bxxx and Txxx cameras. The mounting bayonet is the same as on the Exx series cameras but that camera is not listed for use with this lens. The lens is fitted with electronic ID contacts.

As a supplimentary lens I cannot see why this lens would not work with the Exx series. The dimensions and bayonet mount certainly appear compatible. There is the matter of the ID contacts etc though. According to FLIR, a camera using this lens as an accessory, rather than originally supplied with the camera, requires that the camera be calibrated to use it. This is not uncommon to achieve greatest accuracy. I suspect that the Exx series simpler 'lens selection via menu' does not meet the needs of FLIR to calibrate the camera for use with the 4mm lens. There is a custom lens transmission setting however. That is what I will use and I have the required Black Body thermal references to check the lens characteristics.

Conclusion......

I have purchased an unusual FLIR wide angle lens that will hopefully mate with the Exx series camera OK and provide an excellent field of view for large targets or close up work on PCB's. Barrel distortion is likely but in my use, acceptable. This lens will also work with my other thermal camera if a mounting adapter is used. This is the joy of supplemental lenses rather than interchangeable bespoke camera lens blocks.

Was it a good buy ? ........

Well that depends upon your viewpoint and needs. This lens costs around $3000 from FLIR and I bought it for 10% of that. For a new condition thermal imaging lens from FLIR that is a pretty good deal. Still not exactly a cheap lens though ! The question of high lens costs has been raised on this forum previously. Sadly these are specialist products that use expensive diamond turned (rather than moulded) Germanium lens elements of high quality. For many of us that makes them unaffordable new. I have had some excellent supplemental lens buys on eBay, but they are relatively rare as cameras are often sold with their supplemental lens as a kit. I once purchased a complete PM695 kit just to obtain the supplemental lens that came with it ! The price was right ;)

If this lens does not meet my needs, it is easily resold so the risks are relatively low for me. Spending over $300 on a lens did require some thought though.

Once the lens arrives I will provide some images taken with it to illustrate its wide field of view and likely Barrel distortion that occurs in such a wide angle lens. It is the equivalent of a 18mm lens on a 35mm Film SLR.

Fraser
« Last Edit: April 03, 2018, 12:52:40 am by Fraser »
 
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Offline railrun

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I was the other bidder on this lens
 

Offline Fraser

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I set a max bid of $350 well before the end of the auction and did not expect to win it. Such lenses tend to sell for a lot more. I was surprised that there were only two other bidders on this lens. I have not seen this particular lens for sale on eBay previously. New, it costs twice that of the Exx compatible 0.45x lens ! I honestly expected bidding to go to at least $500.

If I decide to rehome it, I will let you know :)

Fraser
« Last Edit: April 03, 2018, 03:33:45 am by Fraser »
 

Online zucca

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Fraser you are always one step ahead of me.
Once I am done with the E60+ hack I will face the problem of a close-up and wide angle lens.
Can't know what you don't love. St. Augustine
Can't love what you don't know. Zucca
 

Offline Fraser

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@Zucca,

The FLIR lenses for the Exx are scary expensive :(

I bought a couple of X2 FLUKE Tele2 supplimentary lenses cheaply a couple of months ago. They work perfectly with the Exx camera but need a bayonet mount adapter to convert the FLUKE bayonet to the FLIR type. I have been creating such an adapter for 3D printing but other projects have priority at the moment.

Note that the Tele2 is a supplimentary lens design but the Tele1 is a complete Primary lens block assembly.

Fraser
« Last Edit: April 03, 2018, 03:42:11 am by Fraser »
 

Online zucca

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mmm... wide angle... Didn't think too much but a znse 25mm concave lens togheter with a 3d printer could do the job.
Problem is the concave lens, normally laser lens wants to concentrate the rays...
« Last Edit: April 07, 2018, 06:44:05 am by zucca »
Can't know what you don't love. St. Augustine
Can't love what you don't know. Zucca
 

Offline Fraser

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I am no lens expert, but the wide angle lenses I have all contain multiple matched lens elements. I pressume more than one lens element is needed for the Afocal image handling. I did find some ZnSe concave lenses and bought a couple for use as part of a Galileo type telescope. They were very expensive compared to the relatively mass produced bi-convex or plano-convex laser cutter lenses.

I really must make the time to play with some Ray tracing software and some of my lenses to see what is possible with them :)

Fraser

 

Offline Fraser

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I see that there is plenty of information on Afocal lens design on the internet. Basically, an Afocal lens needs at least two lens elements. One is Bi-Convex and the other is Bi-Concave. I own examples of both lens types but whether they are a good match to each other is a different story !

As many will know, such lenses are very common for use on mobile phones these days. Maybe it is not too difficult to make a basic wide angle Afocal lens for the Exx camera. The challenge will be to find two suitably large diameter lens elements in ZnSe, ZnS or Ge.

http://www.opticsforhire.com/blog/2015/11/6/lens-attachments-wide-angle-and-telephoto-lenses

Fraser
 

Online zucca

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Basically, an Afocal lens needs at least two lens elements. One is Bi-Convex and the other is Bi-Concave.

yes, we are now moving into a wild jungle territory, but holy cow we could save tons of money.
I saw in the service menu the "add lens" options which could give us event the opportunity to correct the T measured in a DIY 3D setup.

Ray tracing software

I punched "ray tracing SW" in google and landed somewhere in 3D SW PC image  :horse: ...

"lens design software" will provide much more interesting links.... it is just amazing...

For example...

http://www.opticalsoftware.net/index.php/how_to/lens_design_software/winlens3dbasic



anyone already played with some of those SW toys?

Bare with me Fraser I am still on business trip, I hope to find some time too to follow up.

Can't know what you don't love. St. Augustine
Can't love what you don't know. Zucca
 

Offline Fraser

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I have done some work with optical bench simulation software but I am no expert and the software I used has disappeared from the internet. Some software is heavily tuned towards various BaK and BK glass types etc. It must be remembered that if using Germanium in a design, the refractive index is far greater than glass at ~4.0.  ZnSe is only a little different to glass at ~2.4 so not a great problem. BaK 4 has a RI of around 1.56. The design software I was using could not cope with the high Refractive Index of Ge so I cheated and and entered half the RI whilst doubling the distance between the lens elements. It seemed to work OK :)

It would be good to have a thread that discusses supplimentary lens designs and the results of our software simulations and real world experiments. I know we have some very knowledgeable forum members in the area of DIY optics.

Fraser
« Last Edit: April 04, 2018, 01:43:17 am by Fraser »
 

Offline Fraser

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The wide angle lens arrived today  :)

Does it work with the Exx series cameras ?  Yes, and No .....

The lens is INVERTING, unlike the 45 Degree and 15 Degree supplementary lenses normally fitted to the Exx series. The exx series are not listed in the lens compatibility table so I suspected there may be an issue or two to resolve. I was not expecting image inversion though. The intended host cameras use the same lens mount but also use teh lens contacts to ID it and apply image inversion during the video processing stages. The Exx cameras have no such contacts or image inversion option present in their normal build.

See my new post here for details of my intended next steps.

http://www.eevblog.com/forum/thermal-imaging/bxxx-txxx-axxx-or-scxxx-flashfs-needed-for-wide-angle-lens-project-fraser/

Fraser
 


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