Mirror lenses for deep UV imaging?

[Fandyus]

I'm not sure if this has been discussed here before, but could one possibly get images in deep ultraviolet using a mirror lens constructed with first surface mirrors?

Obviously the issue with deep UV which is around 180nm and shorter is that there is no substance that transmits it, however, what about first surface mirrors? If the mirror is first surface and reflects the light directly without passing through other layers first, shouldn't that work? Or do objects turn matte in deep UV?

[Andy Perrin]

Well, one problem is that many metals become absorbing in deep UV. Silver, for example, is not such a great UV mirror in deep UV:

https://upload.wikim...reflectance.png

 

We have several threads on mirror lenses, though, but just UVA I think.

https://www.ultravio...or-lens-for-uv/

https://www.ultravio...rror-lens-test/

 

JCDowdy reported that there are some that ARE designed for deep UV though, like these:

http://nikongear.net...pic,2814.0.html

http://nikongear.net...hp?topic=7119.0

 

That first one's cutoff is 180nm, and the second cuts at 230nm. That's deep but I think the above issue of the reflectance spectrum of metals probably causes issues past that point.

[Stefano]

Silver has that very interesting (to me at least) "black point" at around 310 nm. David tried to test this but he didn't get black silver: https://www.ultravioletphotography.com/content/index.php/topic/3642-gold-silver-stainless-steel-pewter-cocao-butter-coconut

 

You need very monochromatic light at that wavelength to have that effect, judging from the graph Andy linked. It's like dark water at 980 nm, but requiring an even tighter filter/light source.

 

About substances that transmit deep UV, the one with the deepest reach is LiF, which transmits some as deep as ~110 nm. Below ~100 nm, nothing is transparent until X-rays. A LiF lens would be the ultimate UV-capable lens.

 

Metals are not as reflective in deep UV as they are in visible light, but according to the graph Andy linked aluminium is very good at 200 nm and possibly below. Silver is not good for UV, it is the best metal for mirrors in visible light. Gold is good for mirrors in IR.

[Andy Perrin]

Yeah, my feeling is that the original intention of the thread was to investigate ordinary mirror lenses in deep UV, but if they are based on silver mirrors, it seems like they would probably not work very well. If any common mirror lens uses an aluminum mirror, that would obviously be preferred.

 

The absorption of metals in deep UV was one of the initiating events that led to quantum mechanics. Einstein's 1905 paper on the photoelectric effect explained the absorption:

https://en.wikipedia.org/wiki/Photoelectric_effect

[Guest]

A Zufar 350mm f4.5 recently sold on eBay for $900.

 

 

https://photographyo...ype-quartz.html

 

https://www.ebay.com/itm/154526859917

[Andy Perrin]

Heh, yeah Klaus seems to have an unlimited budget and an amazing ability to ferret out rare lenses.

[Cadmium]

I think the price of such lower UV mirror lenses would stop me, especially given my experience with the few higher UV mirror lenses I have tried,

because the focus of those becomes the issue. Even the ones that transmit UVA well enough have the usual problem with focusing, not much fun,

so in general I can't think or any reason I would use a mirror lens when there are so many other lenses that can focus better and easier.

I think the money can be better spent elsewhere unless you are just building some collection of lenses.

[dabateman]

To answer the subject title, yes.

But they are rare. Especially for focal lengths you want.

 

I have 2 that easily see into UVC. But one is a 15x objective and the other is a 40x objective, both with RMS mounts.

 

I believe they both use aluminum for reflection, rated at 200nm to 20000nm.

 

But I don't know of one designed at say 50mm focal length equivalent.

[Guest]

Heh, yeah Klaus seems to have an unlimited budget and an amazing ability to ferret out rare lenses.

 

I actually thought that price was a bargain considering what other quartz / fluorite objectives are going for these days.

 

If you think about it many well known shorter focal lengths are priced over $1000 per lens element.

 

[Andy Perrin]

Oh, he got a good deal, but he seems to get 10 good deals a year...perhaps I'm exaggerating but, he has a LOT of nice glass. And rarer materials.

 

(I'm very jealous, of course.)

[dabateman]

The serial number on that lens is 72190. Kaus serial number is 18756427.

I wonder how many of those exist. Maybe not very rare.

[JMC]

Not sure Klaus got that Zufar that was recently on ebay. He told me about it. In the end I decided against it, as they wanted 300USD for shipping (I wasn't willing to risk it to the postal system and no insurance). Add in the customs charge and it got expensive. Also, what the advert didn't show was the back of the lens. There was what looked to me like a lot of oxidation of the metal, and as there were no real shots of the inside of the lens I had no info on how the mirrors looked. I like to be able to use lenses I buy, so decided not to take the risk with that one as I didn't want to end up with a 1200USD+ paperweight.

 

There are a few mirror lenses for UV that I have - The Nye 150mm f1.4 mentioned above. I also have a Nye 200mm one which is c-mount and was as far as I know designed for use in the deep UV below 200nm. I also have a Katoptaron Long Distance Microscope - https://www.ultravioletphotography.com/content/index.php/topic/3035-katoptaron-ldm-1s-long-distance-microscope-800mm/page__view__findpost__p__24514

 

Then for microscope work there are quite a few mirror objectives from different manufacturers. Some of these are pure mirror systems, others have quartz and calcium fluoride refractive elements as well.

[Guest]

What a relief! That makes me feel better for missing out after seeing the post by BurstMox on mflenses regarding the lot of Russian lenses for sale. I had been kicking myself ever since. I would have likely also taken pause on a 1/3rd markup on the price for postage and handling. Not to mention every item that I have had shipped from Raf camera looked like the local postal man ran over it with their truck.

 

Also, Klaus blog entry was from 2018. The separate eBay listing I mentioned was this year.

 

Cheers!

[Andy Perrin]

Not to mention every item that I have had shipped from Raf camera looked like the local postal man ran over it with their truck.

Raf camera has never had a problem for me, their adapters are excellent and high quality.

[Guest]

Raf camera has never had a problem for me, their adapters are excellent and high quality.

 

Yes, Raf adapters are also quite durable, and I continue to recommended them to others!

 

In fact, their products could easily withstand whatever failed attempt was made by my local postal service during the shipping and handling.

 

If it wasn't for my uncertainly about state side handling I would definitely order more products from Russia.

 

Cheers

[JMC]

I must admit, I've never had anything but good experiences buying from Russia. Bought plenty from Raf (and other vendors) in the past and they have always turned up on time and in good condition. However they were relatively low value items, not 1200USD+, and for that I wasn't willing to take the risk.

[Guest]

I do apologize for going off topic. It was not my intention.

 

My quarrel is with United States Customs or Unites States Postal Service exclusive.

 

I image if there was a bridge that spanned the Bering Straight then that might make things a little easier for us Yanks. I do order from all over the world and for some reason that's the way it is served. I will continue to order from Raf regardless. They are unique in their offering. I am grateful.

 

Though, It would be nice if Raf had a reseller in my country.

 

Cheers

[JMC]

I do apologize for going off topic. It was not my intention.

 

I wouldn't worry about that, the discussion areas of most topics tends to evolve. This has been less derailed than some.