Author Topic: Trumpf ZnSe lenses - Large diameter long focal length  (Read 3464 times)

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Online Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #50 on: May 25, 2020, 12:35:25 pm »
It is also worth noting that amongst the ten 1.5” diameter lenses I purchased, there were four 5” FL lenses  ;)

In the original purchase that I made of these lenses, to check condition, I saw that the plastic box that my 1.5” diameter lens was in had 5” FL written on it. The actual lens in the box was 7.5” FL but that hinted that there might also be some 5” FL lenses in the stock :) I was correct  :-+

Sadly the lenses are not marked in any way to differentiate between the 7.5” and 5” FL versions. I checked them using my thermal camera and a ruler whilst operating them in Close-up supplemental lens mode in my Exx series camera.

The larger 50mm lenses are all the same 250mm FL.

Fraser
« Last Edit: May 25, 2020, 12:40:11 pm by Fraser »
 

Offline Miek

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #51 on: May 25, 2020, 01:20:32 pm »
Ah, good to know! I spotted some markings on the side of my two 1.5" dia lenses. Looks like I have one of each & the 5.0" FL was used in the pic above.

 

Online Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #52 on: May 25, 2020, 02:04:46 pm »
Mike,

Well spotted Sir  :-+ I will go and check my lenses again. I must get my eyes checked  ;D

Fraser
 

Offline Vipitis

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #53 on: May 25, 2020, 02:11:44 pm »
I chekced the markings on my lenses and all three of my big lenses are 250(mm) and the two small ones are 7.5".

I also got some detail shots of my lenses to highlight the imperfections they got. It's nothing too bad and I don't believe it will end up impacting any imaging I hope to do with them.
 

Offline _Wim_

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #54 on: May 25, 2020, 06:29:08 pm »
The two large lenses I have are also 250, 1 of the small lenses is 250mm, and the other small lens 5". So it seems the smaller lenser were available in 5",7.5" and 250.
 

Offline _Wim_

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #55 on: May 25, 2020, 06:32:43 pm »
I chekced the markings on my lenses and all three of my big lenses are 250(mm) and the two small ones are 7.5".

I also got some detail shots of my lenses to highlight the imperfections they got. It's nothing too bad and I don't believe it will end up impacting any imaging I hope to do with them.

My lenses have simular small issues as seen in the first four lenses in your post.
 

Offline Hydron

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #56 on: May 25, 2020, 09:05:51 pm »
My small one is 7.5" FL, large is 250mm. 5" would have probably been more useful than 7.5", but I can't complain given I also have a good collection of germanium elements (though no other ZnSe, which is why I gave in and bought a pair of these!).

Attached is a pic of what I suspect is the defect that caused my large lens to be retired - is some sort of internal crack which seems to have started at the flat bit on the edge. Looks pretty strange, and stops just shy of the surface, which still appears completely intact. No other obvious damage.

The small one has a very small chip out of an edge and some scratches on the coating in the middle, but nothing too dramatic (would have zero impact in imaging use).

What I did find interesting is the weight of the lenses - significantly heavier than what glass would weigh, much more similar to germanium.
 

Online Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #57 on: May 25, 2020, 09:18:11 pm »
Very sorry to see the defects in the lenses that Vipitis received. Those are worse than I expected, especially the first and last images. The lens shown in the last image is effectively ‘dead’ for optical work. It has suffered overheating and thermal runaway that has damaged its structure. It is sadly of little use for anything optical related now :( I bought my lenses when the seller likely had a greater number to select from for me and I explained I needed relatively unblemished lenses for my thermal camera work. I suspect the choice of lenses with minor imperfections may have been reduced with recent sales. I bought a total of 11 of the 50mm and 11 of the 1.5” sizes and all are in excellent condition. One of the “50mm” diameter lenses is different to the others and is both thicker and slightly larger diameter. It looks in lovely condition and appears to still be 250mm FL.

If anyone has a small black ‘puck’ in the side of their lenses, it is an RFID tag for identification purposes. Not all the lenses have this fitted.

Fraser
« Last Edit: June 12, 2020, 10:35:49 am by Fraser »
 

Offline richnormand

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #58 on: May 25, 2020, 10:06:17 pm »
"If anyone has a small black ‘puck’ in the side of their lenses, it is an RFID tag for identification purposes."

I noted the two 50mm lens had a round black area on the side. I was wondering if it was a soft pad for a set screw (not to crack the lens). That is interesting about the RFID, so each lens could have, in effect, a serial number or other manufacturing data perhaps
None of the 1.5" seem to have that. The 50mm lenses also have a flat on the side too, I assume for orientation?

Minor visual defects but nothing serious for a Keplerian or Galilean telescope application.
Just noted that small negative concave lenses are pretty expensive though!

Thanks for initially pointing out the link Fraser. 
« Last Edit: May 25, 2020, 10:49:41 pm by richnormand »
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Offline artag

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #59 on: May 25, 2020, 10:30:46 pm »
I have one smaller lens and one larger. Two more of each on the way. Both the first two seem undamaged - it appears from comments above that I may not be so lucky with the later purchases.

The larger lens has numbering stamped on the edge and the black dot Fraser mentions. It also has some lettering scratched by hand : I think it reads 'v 9.8" men'

I can't see any machine marking on the smaller lens, but I think it also reads 'v 5" men'
« Last Edit: May 25, 2020, 10:54:19 pm by artag »
 

Offline Hydron

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #60 on: May 25, 2020, 10:46:34 pm »
Hah, sure enough my NFC phone managed to read the little black dot. NXP tag info didn't seem to give anything other than an ID, but I guess that's enough for production tracking etc.

And yes, is a shame about the lack of negative lenses out there - I have a number of positive ones to play with, but the only negative one I have has a fairly low optical power (though it is a nice size at ~45mm dia.)
 

Offline artag

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #61 on: May 25, 2020, 10:51:46 pm »
I noticed various comments about the dangers of grinding ZnSe.

What are the options if we use these as blanks ? And what's needed to do it safely ?

update :

I can answer my own question to some extent : see https://www.crystran.co.uk/userfiles/files/zinc-selenide-znse-msds.pdf

That site has plenty of other useful and interesting papers on IR and other optics

https://www.crystran.co.uk/optical-materials/zinc-selenide-znse
« Last Edit: May 25, 2020, 11:02:21 pm by artag »
 
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Offline conmega

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #62 on: June 12, 2020, 03:45:23 am »
I got 4 sets of each size of lens awhile ago. Been busy integrating my Autoliv2 controller to try them out extensively and look at them.
All of the small ones appear to be 7.5", one is labeled and holding them up side by side to the light the "focusing point" when I get the smallest point of light below them all appears to be the same distance. The larger ones all appear to have the same focal point as-well. But I have no labels on any of them. 3 of them have the RFID puck but I don't know if I have an RFID reader for them handy.

The small ones work GREAT for getting an extremely close focal point on the Autoliv2, I had previously screwed out the lens a bit to get it to about 2~ft but you end up with distortion from the way the lens is in the Autoliv... Without setting that back and just throwing the lens in front it really clears it up and just yea wow. You can see below how far I had it from my board and what it looked like on video. (this is with histogram and an iron palette mind you, this is not what cames straight out of the camera) Frankly I didn't have the focus perfect... Trying to take a photo of what I was doing while holding it was a bit difficult. Will eventually try to 3D print an adapter for the Autoliv2. I will note I am not keeping all 8 lenses... 4 of them are going off to friends, I made a bulk order to the US to help save on shipping for us all.
I will say these look clearer on video than the germanium protective covers that come on the Autolivs. Really nice lenses especially for the price.




All of my lenses appear in great shape. With only a few minor spots on some of the smaller lenses and the large ones look almost perfect.


 
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Online Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #63 on: June 12, 2020, 10:17:49 am »
 :-+
 

Offline Ultrapurple

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #64 on: June 19, 2020, 09:48:45 am »
I now have a few of these lenses and mine are all essentially 'as-new'. Only one has any damage - slight scratches - and that was down to me not realising just how soft the lens (or at least the coating) actually is. I was wearing new white cotton gloves to handle the lenses and that was enough to cause scratches when I absent-mindedly tried to remove a speck of dust :(

Still, the scratches are only superficial and (as they say in all the eBay ads for lenses) "don't affect image quality..."
« Last Edit: June 19, 2020, 01:49:31 pm by Ultrapurple »
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