Author Topic: Trumpf ZnSe lenses - Large diameter long focal length  (Read 2333 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.
 

Online _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.
 

Online _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
 


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