(Data now provided) Therm-App 19mm lens technical details ?

[Fraser]

My turn to ask for some help

I have just purchased a Therm-App 19mm lens for experimentation. There seems little technical information on this lens apart from FOV. I checked the Opgal site for similar lenses but that was also unhelpful.

The lens is coming from the USA so will take around 2 weeks to get to me. In the mean time I would love to gather some information on it, if available.

I know only that it is an F1.1 with a HFOV of around 20 Degrees when used on the Therm-App basic camera.

I would appreciate any additional information from owners of such a lens. Useful information includes...

1. Lens barrel diameter
2. Lens thread diameter and pitch
3. Actual lens element visible diameter (I am guessing around 20mm)
4. Rear of lens images as I have not seen this side of the lens.
5. Is it Germanium or Chalcogenide IR glass ? I thought Germanium but may be wrong.
6. What is the approximate back focus distance when set to infinity focus ? This may be hard to judge so even the approximate distance between the rear of the lens element and the microbolometer window would be useful.
7. Has anyone found a threaded adapter compatible with the lens thread ? I know unlikely so I may have to design one for 3D printing.
8. Has anyone seen an Opgal technical drawing of the lens ? Some manufacturers produce useful drawings showing camera and lens dimensional data. Theses can be very useful when adapting a lens to other cameras.


Well there you go. Lots of questions but I am just putting them here in case a Therm-App owner has found more technical detail on the lens.

Many Thanks in advance for any and all comments on this neat little lens. It cost me $43 so I thought it worth a look. I may even operate it in reverse as a thermal microscope lens

Fraser

[Vipitis]

well.... I was like a hand away from getting it myself. there was a secondary listing at a higher price that seems to be still up with 1 left: https://www.ebay.com/itm/Therm-App-TA190000-0001-Additional-Lens-19-mm/192614732163?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

I will try to get it... 16$ of shipping is worth it I guess... I might take it apart and experiment with the elements myself. This "experimental kit" costs three times as much:
 https://www.ebay.com/itm/Germanium-Linsen-Ge-IR-Objektiv-W%C3%A4rmebildkamera-Set-f-15mm-Kuppel-Konvex-lens/183333604933?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

Hoping to get some information on it as well.

I might just use it as afocal lens on my CAT S60 - or have some fun by using it directly without the case window as I plan on taking my phone apart for a battery swap soon.

It will be fun and it isn't too expensive.

[Fraser]

Hiya,

The seller is the same but using different account names. It might be worth asking for the remaining lens to be discounted down to the price I paid. Amazon Warehouse have one of these lenses for $33 but will not ship to the UK

Fraser

[Fraser]

Regarding that experimenters kit. I saw that and it looks like the lens element set from an E2V ARGUS camera. I have some of those and they look similar, if not the same.

Fraser

[Vipitis]

Welp, it just vanished moments after writing my reply... One refresh and it was out of stock.

There are some more listings but no international shipping. So I will pass and keep my eyes open. Maybe I will just get some different lenses for lasers and see what works.

[mahony]

The thread seems to be M25x0.5 according to this discussion on flickr:
https://www.flickr.com/groups/2713182@N24/discuss/72157650531006833/

I was quite sure I read this somewhere and I think encryptededdie is the same user as here in the forum. Another interesting fact he states is that the 19mm and 35mm lenses are from Ophir which makes sens as Opgal and Ophir are both based in Israel. Here is a link to one of Ophirs catalogs.
https://www.ophiropt.com/optics/lens_sub_assembly/catalog/ophir_supir_lens_catalog.pdf

I think the lens in question should be with part number 65221 on page 72 in the pdf. The image seems to be from the backside but there is a drawing that seem to resamble the outline of the lens quite good.

I though about byuing one myself too but as the TE-V1 comes with a 19mm (from Umicore actually: https://eom.umicore.com/en/infrared-optics/products/thermal-imaging-lenses/19-mm-f-10-athermalized-infrared-lens/) by default it would have been of no special use - altough it is worth noting, that both cameras/lenses use the same thread and also the back working distance of both lenses seems to be very similar - so it is quite likely that lenses between ThermApp and Thermal Expert V1 are exchangeable without huge troubles.

If someone stumbles upon the 35mm equivalent I would be definately interested. ;-)

[Fraser]

Vipitis,

Hmmm I suspect there was only ever one 19mm lens for sale and the seller had it listed on two accounts. The seller names were different but the auction graphics and content identical. When I bought the lens I suspect they cancelled the other auction as they no longer had stock. I have seen sellers listing the same item multiple times at different prices and in different categories. Not sure why, maybe just a sales technique.

Fraser

[Fraser]

Mahony,

Many thanks for the information. Very much appreciated 

Fraser

[Fraser]

I just checked my Camera lens mount spares box and I already have a 25mm x 0.5mm lens mount plate. I bought it for another project but that turned out needing a 24.5mm x 0.5mm mount so this one was no use. Lucky I kept it

Fraser

[Fraser]

I just had a look at the link that Mahony provided to Ophir.

I concur that the 19mm lens they show in their catalogue looks to be the one I have purchased. Having looked at the specs it is a very useful lens. On a 160 x 120 pixel 25um pixel core it provides 11.9 Degrees FOV and even narrower on a 17um or 12um pixel die and it is compatible with common QVGA microbolometer sizes providing larger FOV's. Very useful to have in the lens box.

Unsurprisingly the lens appears to be a hybrid using Germanium in the front Objective element and ZnSe in the rear element. This is not uncommon, even on expensive lenses. ZnSe has excellent transmission characteristics.

Fraser

[Fraser]

The Therm App 19mm lens arrived today.

What a neat little lens it is 

The front lens element is Germanium or Chalcogenide IR glass and the rear element is ZnSe as I suspected.
It is a nice doublet of decent size. Very pleased with it.

Fraser

[Fraser]

Side view