Author Topic: Trumpf ZnSe lenses - Large diameter long focal length  (Read 2332 times)

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Offline Fraser

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Trumpf ZnSe lenses - Large diameter long focal length
« on: May 01, 2020, 09:17:44 am »
In case anyone is interested, I found a seller of used Trumpf ZnSe laser focussing lenses on eBay. They are listed at £3 and £4 each  :-+

These lenses are nice and large, very high transmission and professional grade. They are available in two types.
1.5” diameter with 7.5” FL and 50mm diameter with 250mm FL. These are used lenses so some may have small burns in them, but the ones I received were in great condition. These were all removed from service on Trumpf high powered CO2 cutting lasers when they failed routine inspection. It appears that absolutely no degradation is permissible in these lenses due to the high powers being used so they get removed before they get badly burnt.

I bought ten of each for experimentation. These are scary expensive new but of course these are used inspection rejects so bear this in mind. They are certainly large lumps of high quality AR coated ZnSe and the diameters plus focal lengths are greater than most cheap Chinese ZnSe CO2 laser lenses.

https://www.ebay.co.uk/itm/Genuine-Trumpf-CO2-Laser-250-Focusing-Lens/254574634319?hash=item3b45d4a54f:g:WS8AAOSwZgheIy46

I have no connection to the seller or the items being sold. This is just a ‘public service’ announcement :)

Fraser
« Last Edit: May 01, 2020, 09:53:05 am by Fraser »
 
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Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #1 on: May 01, 2020, 09:36:20 am »
Pictures of my lenses. I initially bought 2 of each to check quality so now have 12 of each for experimentation :)

Specified absorbance is better than 0.23%

Fraser
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #2 on: May 01, 2020, 09:56:37 am »
As a side note, the seller uses these inspection rejects in his ‘SteamPunk’ designs  :-+
He knows about the safety issues if they are drilled or broken apart though so he is not daft with them. He seems to have plenty of stock.

Fraser
« Last Edit: May 01, 2020, 10:14:47 am by Fraser »
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #3 on: May 01, 2020, 10:12:48 am »
With regard to what these lenses may be used for, they are a little high on the focal length front for close-up lenses but would make interesting objective lenses for thermal telescopes :) I like working with ZnSe lenses as you can experiment with them using visible light to see the effect of changes in your design without the need for a thermal camera. Focus distances are, of course, slightly different when setting the lens assembly for Thermal imaging.

In case anyone is interested, these lenses are around £400+VAT each new.

Fraser
 

Offline Vipitis

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #4 on: May 01, 2020, 10:34:54 am »
Thanks for this tip. I have contacted the seller to see if shipping to Germany is an option; for the given prices I will try to pick up two of each to add to my lens element collection, I got nothing particular planned but might come in useful for something.
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #5 on: May 01, 2020, 10:38:45 am »
Vipitis,

You are most welcome  :-+

These lenses caught my eye because they are unusually large diameter and long focal length. Anything different from the common CO2 laser lenses we see on eBay is normally very expensive.

Make sure you ask the seller for lenses that are not obviously blemished as he is a really friendly chap and selected nice examples for me. He said they are all pretty good though so no burned up lenses  :)

Fraser
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #6 on: May 01, 2020, 10:55:30 am »
For those unaware of the failures that can occur in high powered laser focus lenses made of ZnSe (and likely other materials too). The lens must be very high transmission to prevent self heating that will destroy the lens. If a lens gets dirty it will heat up very quickly. These lenses are considered consumables in the Trumpf high powered laser cutting machines. They are inspected for defects and degradation regularly and any that are showing signs of stress are removed from service. A lens can be described as ‘stressed’ after inspection but look perfect to the human eye. The lens likely has stress marks that show up under specific tests designed to highlight such. The lenses appear to work fine in the thermal imaging role however. Some lenses will have tiny ‘poc’ marks in the AR  coating. I do not know what causes this but it could be just lens contamination with dirt causing localised heating or some off axis component of the laser beam causing a hot spot ? The spots are often very small and can often be ignored or tolerated considering the low cost of these inspection rejects.
A ZnSe lens can fail in a more spectacular way in a high powered laser cutting system when it actually starts to absorb too much laser energy inside itself due to internal stress damage. The lens literally burns up and you get a large ‘bullseye’ in its centre. Such a lens is total scrap and not recommended for handling due to health concerns. You will see high power ZnSe lenses that appear to have a ‘bloom’ or rainbow effect on their surface. These are usually another form of inspection reject that has just come to the end of its operational life and started to overheat but was removed from service before the laser fried it completely. None of the lenses I have received from the above detailed auction look in any way fried or bloomed. In fact they look to be in very good condition considering they were coping with multi KW laser powers. The original user of these lasers clearly has regular lens inspections.

If you want absolutely perfect lenses of this specification, you will need to buy a new one. These are, however, perfect for lens experimentation and should be fine for thermal camera applications. Buyers are not risking much money here anyway  ;D

High powered lasers are not tolerant of poor quality optics so these will likely be far superior to cheap low powered ZnSe lense that we buy for less than $30 on eBay.

Fraser
« Last Edit: May 01, 2020, 12:02:34 pm by Fraser »
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #7 on: May 01, 2020, 11:13:59 am »
An interesting article on laser cutter lens damage. I might add that none of the lenses I received look anything like those shown here, as can be seen in my pictures. The Trumpf lenses are protected from dirt and spatter by a window that sits between the ZnSe lens and the material being cut.

https://www.mate.com/co2-lens-failure-causes-part-1-lens-build-up/

Note the comment about thermal runaway ! As ZnSe gets hotter it can reach a point of reducing transmission and so thermal runaway begins. Such thermal runaway can only end badly for the lens  :(
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #8 on: May 01, 2020, 11:57:45 am »
Another interesting page detailing the ugly damage that can occur to a ZnSe lens used in high power laser cutter applications. Again, none of the ones I received looked like the examples shown so fear not ;)

https://www.ophiropt.com/co2-lasers-optics/focusing-lens/knowledge-center/lens-failure

Fraser
 

Offline RBsonic

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #9 on: May 01, 2020, 05:43:30 pm »
Can this lens be used for inspection of small smd componnents?
 

Offline SeanB

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #10 on: May 01, 2020, 06:23:47 pm »
Sadly does not ship to me though.....
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #11 on: May 01, 2020, 06:54:49 pm »
SeanB,

Have you asked him as he seems a really friendly chap :)

If so did you tell him you are from the EEVBlog as he is aware that I have mentioned his lenses here. It may help ? The lenses are not very heavy or bulky and if you accept risk of loss he might come to the party.

Fraser
« Last Edit: May 01, 2020, 06:56:38 pm by Fraser »
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #12 on: May 01, 2020, 06:58:17 pm »
RBsonic.

No, the focus point is too far away for SMD use. You need something with an FL of 100mm or less. Lots of Chinese ZnSe lenses available cheaply for that task  :)

Fraser
 

Offline Vipitis

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #13 on: May 01, 2020, 07:43:59 pm »
it looks like I ended up getting 1 lens for 4GBP + 4 shipping as I had a little trouble around the eBay buy now interface and requesting a shipping price. We'll see what quality mine ends up as the other listing is gone.
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #14 on: May 01, 2020, 11:15:27 pm »
Vipitis,

The seller lists individual lenses but you can ask him to quote for more than one with combined shipping and he will create a custom listing for you. That is how I bought 10 of each.

If you contact the seller and tell him what you want, he will likely help you.

Fraser
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #15 on: May 01, 2020, 11:53:50 pm »
I have checked all my lenses and they are all in nice condition. Some do have the odd tiny black spot that I previously mentioned, but nothing terrible. I checked the lenses using the crossed polariser technique and they all have some evidence of stress. When tested on a FLIR E60+ as a close-up lens, there was no issue with the images produced and the transmission loss was very low, as expected. I suspect that these lenses were removed from service due to the evidence of internal stress revealed by the crossed polariser test.

From what I can see, these lenses are more than adequate for thermal camera telescope or other optical experiments :)

As a side note. I thought the seller might have some 5” FL 1.5” diameter lenses and asked that he include some in my order if possible. He sent me four as part of my order for 10 of the 1.5” diameter lenses :) I do not know if he has any more of the 5” FL lenses.

Fraser
 
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Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #16 on: May 02, 2020, 10:29:53 am »
The lens auctions are active again. For some reason the seller is not providing a multiple item listing. If you want more than one lens, contact him and ask for a custom listing.
 

Offline RBsonic

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #17 on: May 02, 2020, 05:18:43 pm »
Can you some thermal fotos with and without lens?
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #18 on: May 02, 2020, 06:26:42 pm »
It is not a close-up lens. It is best used as part of an optical system such as a Keplerian or Galileo telescope. An image through the single lens element would not reveal very much as the whole lens surface is not being used by my E60+ cameras FOV at close quarters and transmission is already known to be excellent. What are you trying to find out from a picture please ?

Fraser
 

Offline RBsonic

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #19 on: May 02, 2020, 08:05:24 pm »
I just want to see quality of image through lens.
 

Offline _Wim_

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #20 on: May 02, 2020, 08:16:31 pm »
Thanks for this tip. I have contacted the seller to see if shipping to Germany is an option; for the given prices I will try to pick up two of each to add to my lens element collection, I got nothing particular planned but might come in useful for something.

Done exactly the same. Thanks for the great tip Fraser!  :-+
 

Offline winternight69

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #21 on: May 02, 2020, 08:26:14 pm »
Hi, I am a seller from eBay for Trumpf lenses.I have some numbers in my stock,most was collected for my hobby as steampunk artist. I do provide some links to my YouTube channel to see as a different aspects for using this lenses. Thank you for watching.
 


 

Offline KE5FX

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #22 on: May 02, 2020, 08:34:02 pm »
A ZnSe lens can fail in a more spectacular way in a high powered laser cutting system when it actually starts to absorb too much laser energy inside itself due to internal stress damage. The lens literally burns up and you get a large ‘bullseye’ in its centre. Such a lens is total scrap and not recommended for handling due to health concerns.

I thought this was interesting, and did some Googling.  Contrary to my impression, these lenses aren't just chunks of plastic that have been doped with zinc selenide.  They actually are zinc selenide.  So there's quite a bit of selenium that can be liberated under the right (wrong) conditions. 

It would certainly be smart to wear a good respirator if you ever need to grind or machine one of these.  I didn't see any specific references to dust hazards, but they definitely need to be kept well out of reach of infants and small children.  If swallowed, they can generate H2Se gas in the stomach, which is described as being even more toxic than H2S.  One of those things that gets a '4' on the hazmat diamond for both health and flammability.    :scared:  They look a little too much like candy for me to be entirely comfortable using them as decorations.
 

Offline _Wim_

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #23 on: May 02, 2020, 08:35:53 pm »
Hi, I am a seller from eBay for Trumpf lenses.I have some numbers in my stock,most was collected for my hobby as steampunk artist. I do provide some links to my YouTube channel to see as a different aspects for using this lenses. Thank you for watching.
 




Welcome to the forum. Incredible builds!  :-+  Complete different use of ZnSe lenses as we typically would use them. Much more beautiful!
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #24 on: May 02, 2020, 09:23:00 pm »
Winternight69,

Welcome to the forum  :-+

I love the Steampunk Art  :-+ :-+ :-+

Fraser
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #25 on: May 02, 2020, 09:35:33 pm »
RBSonic,

I will see what I can do but not sure how good the results will be just looking through the lens with the E60+. No time to make a decent Keplerian telescope at the moment.

Fraser
 

Offline winternight69

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #26 on: May 02, 2020, 11:19:56 pm »
Thanks a lot to everyone! As I am a guest here if someone need to contact me about lenses use my Ebay account.  I try to do as much as can. If someone needs to ship it outside the Europe will not be a problem, but postage fees could be different. I'll try to find the best options for you. I have two type of lenses, they are taking out of service from machine and placed in original packaging straight away. Most of them in quiet good conditions. I am not keeping burned or damaged lenses, may have some small imperfection and maybe some needs proper clean, which is set up a special procedure to avoid for scratching them. I am not providing a cleaning . Any questions I do answer from my Ebay account.
Best regards
 
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Offline _Wim_

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #27 on: May 03, 2020, 05:46:53 am »
winternight69, as a transition from Steampunk art to our electronics hobby, a nixie tube clock project looks ideal for you:  ;)

https://www.eevblog.com/2016/11/26/eevblog-948-nixie-tube-display-project-part-1/

 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #28 on: May 03, 2020, 12:13:06 pm »
Winternight69,

I must say, I love the Steampunk fish  :-+

Close study reveals the complexity of the build. Most impressive. I am thinking the spine of the Fisk is made from laser cutter copper output nozzles. It is great to see industrial ‘scrap’ turned into something beautiful  :-+

I can imagine that steampunk fish exploring the depths of an ocean on a far off world where life is an organic/machine hybrid rather than purely organic  :)

Wonderful art, simply wonderful. I had not spent much time looking at Steampunk art.... I shall have to study it some more. I definitely prefer Steampunk ‘animals’, likely because I love organic animals.

Fraser
 

Offline NiallxD

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #29 on: May 03, 2020, 08:22:06 pm »
Fraser,

Cheers for highlighting these for me, I bought some a while back and they were far too small for my use so sent them back to Amazon. Bought the 38 & 50mm lenses from Winternight69,

Looking forward to doing some tinkering. I've got some kind of thermal telescope in mind, so if anything pops to mind let me know. You are significantly more experienced in all this than I am,

Cheers again!

Niall
 

Offline ArsenioDev

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #30 on: May 05, 2020, 10:05:07 pm »
Darn, JUST missed these lenses available.  :'( 
Was hoping to snag some to do telescope work but alas
 

Offline eliocor

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #31 on: May 05, 2020, 11:54:23 pm »
@ArsenioDev:
it seems to me they are yet available: https://www.ebay.co.uk/sch/winternight69/m.html
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #32 on: May 06, 2020, 03:15:50 am »
@ArsenioDev,

If you contact the seller via ebay and let him know how many of each type you want, he will create a special auction for you with the appropriate postage shown.

Fraser
 

Offline ArsenioDev

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #33 on: May 07, 2020, 04:38:51 pm »
OH, hrm. When I checked his page it showed no items listed. Will run some numbers later today on which ones I need. Thanks for the heads up
 

Offline Miek

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #34 on: May 07, 2020, 08:14:01 pm »
Thanks for sharing this Fraser. I now have a couple of each size on the way :D
 

Offline NiallxD

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #35 on: May 07, 2020, 09:10:36 pm »
@Winternight95

Thanks for the lenses! Time to have some fun!

Niall!
 

Offline Vipitis

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #36 on: May 12, 2020, 11:00:20 am »
I got my first lens today, it looks pristine and transmission looks fairly well. Next order is placed already, got the 2 pack. Will eventually put all my lens elements together and see what I can make, maybe replace the broken element - getting my 3D printer operational again would be a good start.

Thanks for the listing and pointer!
 

Offline _Wim_

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #37 on: May 18, 2020, 06:07:40 pm »
Done exactly the same. Thanks for the great tip Fraser!  :-+

My set of lenses arrived also today. They look fantastic. Thanks winternight69 & Fraser for making this possible!
 

Offline Vipitis

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #38 on: May 19, 2020, 12:29:17 pm »
my set of 4 lenses arrived today, definitely not as pristine of a condition as the first one I got. But as I ordered later I must have been a little ways down the chain of quality picks. Still very much good enough for imaging and experiments. I set them aside for now as I got a other things to do and can't put much time towards working on my camera systems. Will update when I made use of the elements.
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #39 on: May 19, 2020, 04:27:45 pm »
All we need now is an affordable source of Plano Concave, bi-concave or Negative meniscus lenses and we have the basics of a supplemental mount Galilean telescope  :-+

Fraser
« Last Edit: May 19, 2020, 04:42:14 pm by Fraser »
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #40 on: May 19, 2020, 04:31:35 pm »
Vipitis,

What issues do your lenses have ? It is not unusual to have a tiny black dot laser burn but none of my lenses have anything really bad wrong with them. Small blemishes on an Objective lens are not in focus and will hopefully not be visible at the resolutions that we work at.

Fraser
 

Offline Miek

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #41 on: May 22, 2020, 06:25:50 pm »
They also work rather well as close-up lenses  ;D
 
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Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #42 on: May 22, 2020, 06:45:39 pm »
Mike,

Interesting  :-+

I see you have a 3D print design for a lens mount on the PM series  :-+ :-+ Would you be willing to share that mount design please ? I need one and have just not had the time to concentrate on it.

Fraser
 

Offline Miek

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #43 on: May 22, 2020, 07:13:22 pm »
Sure! I've attached some sketches of the critical dimensions, and a zip of the STLs & SolveSpace project files.
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #44 on: May 22, 2020, 10:17:06 pm »
Thanks Miek  :-+

Great work  :-+ :-+  That design will help me with developing other lens adapters for my PM series cameras.

Thank you for sharing your hard work.

Fraser
« Last Edit: May 22, 2020, 10:23:38 pm by Fraser »
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #45 on: May 23, 2020, 11:09:32 pm »
Miek,

I just completed the printing of the two PM series lens mounts in ABS  :)

They are excellent  :-+ Thanks again for sharing.

Picture attached.
Fraser
« Last Edit: May 23, 2020, 11:17:14 pm by Fraser »
 

Offline RBsonic

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #46 on: May 24, 2020, 07:09:43 pm »

Fraser

Can you post some thermal photos with lens and without?
« Last Edit: May 24, 2020, 07:15:37 pm by RBsonic »
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #47 on: May 24, 2020, 07:51:58 pm »
No PM series cameras to hand at the moment. Regret I cannot help but Miek may be able to help. He has already provided some examples in this thread  :)

Fraser
« Last Edit: May 24, 2020, 07:59:11 pm by Fraser »
 

Offline Fraser

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #48 on: May 24, 2020, 07:57:02 pm »
RBSonic,

Please also remember that I do not recommend these lenses for PCB work as 7.5 Inches is a little too far away for detailed SMD work. 100mm/4 inches is better as a general PCB close-up lenses. Miek's pictures tell you something about the lenses though. No nasty image distortion visible.

Fraser
 

Offline Miek

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Re: Trumpf ZnSe lenses - Large diameter long focal length
« Reply #49 on: May 25, 2020, 12:29:37 pm »
I just completed the printing of the two PM series lens mounts in ABS  :)

Nice!  :-+

No PM series cameras to hand at the moment. Regret I cannot help but Miek may be able to help. He has already provided some examples in this thread  :)

Yep, in pictures I posted above 'far' is no supplementary lens, 'close' is with the 50mm diameter lens, and 'closer' is the 1.5" diameter lens.
 

Offline 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.

 

Offline 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.
 

Offline 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 ticker 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: May 25, 2020, 09:21:22 pm 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 »
REPAIR, RENEW, REUSE, RECYCLE, REDUCE, REPURPOSE....
 

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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