How hard is it to create a DIY Thermal Zoom Lens?

[AranLeer]

Hello Everyone.
I've recently purchased one of the "Infiray P2 Pro" cameras, which will arrive soon. I like that it comes with a magnetic macro lens attachment for close-up work, but it did make me wonder - would it be possible to make a DIY magnetically-attachable zoom lens for it as well?

I have some experience making visible-light zoom lenses, so my assumption is it would be possible to get a high-magnification optical lens, and a larger low magnification objective lens, and then build them into a cylinder where the objective lens can screw in or out for focus.

But does anyone have experience building something like this for Thermal?

[Fraser]

A fellow forum member created a telephoto supplemental lens and documented it here and in a instructable....

https://www.instructables.com/Diy-Thermal-Camera-Telephoto-Converter/

Note these are fixed telephoto lenses and not a variable magnification zoom.

I bought FLUKE telephoto X2 supplemental lenses for less than £200 as it was cheaper than buying the parts to make one. Those lenses match well into many camera lens systems. I was also fortunate enough to buy a Torrey Pines X3 supplemental lens at a good price but those are uncommon and normally expensive.

The problem you face is the sourcing of suitable lens elements at a sensible cost. Small Plano convex lenses are relatively common but larger diameters, bi-concave and meniscus lenses often have to be harvested from surplus complete lenses and cameras. New LWIR AR coated lenses can get very expensive if not a common type used for laser engravers etc.

Fraser

[AranLeer]

Ok, thank you for the information!
I really appreciate it.

[Vipitis]

Another forum member has DIY zoom lenses using salvaged lens elements and 3D printing housing, threads. There might be a thread about it, but they are also selling them on (German-) eBay.

My experience with 'building" a lens was to first source Elements (find some old or broken camera on ebay, get spares from bill, etc) and just trail and error with an improvised optical bench till you find some combination that works. 3D print the mechanics. Without knowing the parameters of the lens elements it's impossible to do any calculations, but if you buy elements where you know the parameters you might be able to do it. Germanium has a really high index of refraction, so 2 or 3 elements might do it.

If you take the lens off your camera it's a different problem but you can likely just adapt any given lens that you can find.

[cejoba]

If anyone done it successfully, he will be my hero. I've dreamed for a zoomable thermal camera for too long.
I've heard the reason no one makes it is because zoom lens will be small aperture, so it will only available for cooled high sensitivity cameras. Don't know if it's true though.

[Fraser]

Cejoba,

Ophir make good variable magnification zoom lenses with respectable speeds but the prices are high.

https://www.ophiropt.com/infrared/long-range-zoom-lenses/

Fraser

[ArsenioDev]

I was at AUSA earlier this month, and asked around several vendors about zoom LWIR lenses, Teledyne has some, and are "not too bad", got another spot quote for $12K for a 12-150mm zoom unit with controller (very nice)

[Vipitis]

Related thread: https://www.eevblog.com/forum/thermal-imaging/seek-reveal-and-reveal-pro-supplemental-lens-adapters/

For reference

[AkiTaiyo]

Several industrial thermal imaging companies make narrow FoV cameras for applications such as flare stack monitoring.  Ametek Land do a 6x4° lens option for an 8-14 camera for this application.

Usually, radiometric thermal cameras don't have adjustable lens systems due to the calibration effort involved in getting accurate measurements.

[cejoba]

Cejoba,

Ophir make good variable magnification zoom lenses with respectable speeds but the prices are high.

https://www.ophiropt.com/infrared/long-range-zoom-lenses/

Fraser

Good find, but this kind of company/website is not really friendly to us hobbists, they even require quote and not sell directly...

[Fraser]

Cejoba,

Provided only as an example of what is available The prices are horrendous so I would not expect a hobbyist to buy such a lens. It just shows that such are available with decent speeds 

Fraser

[cejoba]

I found "Hurley IR LRTI" on ebay, which have 30-90mm f1.0 LWIR lens.
I don't know what's inside that camera though.

[cejoba]

I just found several more zooming LWIR lens, by Flir and Tamron, which are more reliable companies.

https://www.flir.com/products/lwir-zoom-lens-assemblies/?model=2280-300

https://www.tamron.biz/en/data/thermal/index.html

I don't know the price and availability though, and they looks expensive...

[ArsenioDev]

You're looking in the range of several >5 kilobucks, the FLIR ones start around 9K and work their way up. 

[Hawaka]

@Fraser mention the Fotric thermal camera in another thread and I had a look out of curiosity. Some appear to come with a set of different lens. I wonder how easy and how cheap it would be to just get the lens and make an adapter.

[Fraser]

I adapt lenses to mount in camera bodies for which they were never intended and it can be easy or virtually impossible due to the specifications of the lens assembly.

Key issues to investigate if considering buying a lens to mount on a camera body in place of the original lens assembly……

1. Image Circle dimensions vs microbolometer active detection area dimensions
2. Lens back focus distance vs what is achievable using an adapter on the camera body. Very important and essential to get exactly right for a Zoom lens to maintain focus through Zoom range.
3. Lens mount design adaptability to mount on camera body. Some are easy, others are not !
4. Lens resolution. Some older supply’s lenses may not be intended to work well with modern 12um or 17um pixel microbolometers.
5. Camera flat field including lens…. The camera is calibrated for a flat field with a particular lens. In some cases, fitting a different lens can cause effects such as a permanent gain differential circle on images.
6. Camera measurement accuracy ….. a different lens requires a new calibration table in the camera if measurements are to be accurate.
7. Ergonomics ….  Mounting a large, possibly heavy, lens on a cameras body can destroy its balance and can even stress the lens mount. Some lenses come as a skeleton and need an enclosure to protect them in use.
8. Ensure the AR coating on any undocumented lens matches the needs of the camera ! MWIR lenses will not normally work on a LWIR camera.

Finally, supplemental lenses may be mounted in front of the original camera lens and I have used such lenses with cameras for which they were not intended. Such lenses are considered single FOV and are not variable magnification like a true Zoom.

In military applications it is not uncommon to have a dual FOV primary lens with fast transition between the two at the touch of a button. This provides general field of view observation and then detailed observation with a much smaller FOV. Basically …. Heat source detection and then identification prior to potentially targeting it. If buying a surplus military camera that is fitted with such a lens, be careful to check whether the camera is/was MWIR or LWIR.

Fraser

[cejoba]

3. Lens mount design adaptability to mount on camera body.

So how about this?

[Fraser]

 

[bap2703]

Better than duct tape