UV to Visible Light Converters

[Foxfire]

Something i thought may be interesting. Just found these Lumilass fluorescent glasses that should convert faint UV source of 200 – 400 nm into visible. 

Looks like these have a potential for UVR imaging/photography. Any ideas how to do it, use these? 

[ulf]

It is some interesting glass materials. I am sure the green one is most usable as its sensitivity covers the deeper ranges of UV best.

The rest can easily be imaged in other ways

 

An experimental setup would look like this:

A lens with a good deep UV-reach like an UV-Nikkor - mounted on extensions that focus the image on/in the glass disc just as if it was a camera sensor - a camera with a macro lens that focus on/in the glass disc through some light tight tubing. Focussing set at the same focal plane for the UV-lens and the macro lens in the glass disc.

 

There might not be a very good resolution and likely some light halos as the fluorescence will occur in all of the glass disc material even if it will be mot bright at the focus plane.

 

Depending on how strong the fluorescence is there might be a need for some VIS rejecting filter on the UV-lens.

[ulf]

To just experiment with the setup as a concept, but with easier wavelengths can be done with a GG420 filter glass or similar and a 365nm light source. 

I would do that experiment in a dark room using a good stock camera.

The GG420 show strong fluorescence for UV-A and have an optical depth just like the materials Foxfire found.

 

This experiment can give an idea of possible resolutions and some of the basic problems with this type of imaging. 

When shifting to deeper UV with correct materials and light sources will be even more difficult.

[Foxfire]

Thanks, my initial thought was that to place such fluorescing glass directly in front of a camera sensor, somehow, but the idea that to sandwich it between UV transmitting lens and macro lens seems more doable. I might try this concept with one of my strongly fluorescent UV cut filter.
Probably the UV transmitting lens could also be replaced with some pinhole-thing. Even if the image quality can't be expected to be very high, it looks like an interesting and less explored approach for UV-world visualization.

 

Attractive about theses Lumilass glasses is that these could be used for converting UV-B and UV-C into visible, and also the availability in red, green and blue emissions - this is like offering an opportunity for color images.

[dabateman]

Well it has been explored and this is basically how the Sirchie imagers work.

There is a UV lens, like a 60mm macro or 25mm optic. This focus the light onto a phosphorus coated screen. Then you place your eye or use a camera adapter to look at the green screen image. 

 

[colinbm]

42 minutes ago, dabateman said:

Well it has been explored and this is basically how the Sirchie imagers work.

There is a UV lens, like a 60mm macro or 25mm optic. This focus the light onto a phosphorus coated screen. Then you place your eye or use a camera adapter to look at the green screen image. 

 

Dave I have looked for phosphorus coated screens without any luck.
Maybe these Lumilass fluorescent screens might be available ?

[ulf]

47 minutes ago, dabateman said:

Well it has been explored and this is basically how the Sirchie imagers work.

There is a UV lens, like a 60mm macro or 25mm optic. This focus the light onto a phosphorus coated screen. Then you place your eye or use a camera adapter to look at the green screen image. 

 

The difference here is that it is no a coated surface, bur that you have fluorescence in the depth of the glass material

[Foxfire]

1 hour ago, dabateman said:

Well it has been explored and this is basically how the Sirchie imagers work.

Sirchie imagers, Great! meaning that the concept works. Maybe it's even possible to home-build something for higher energy radiation, with scintillators. Had in mind something like a half year exposure time pinhole camera for x-ray landscape imaging.

[Andy Perrin]

For X-rays (and my goodness people, BE CAREFUL), dental X-ray CCD imagers are available very cheaply on ebay, as are X-ray sources. Just a few hundred dollars for an imager. You don’t need to bother with fluorescent screens. The problem is the optics and the safety issues, not making an image. 
 

I mean, personally I would love to build a micro-CT machine, but I also don’t want cancer. 

—-

 

Back to the main topic, I used a upconverting “fluorescent” (actually anti-Stokes effect) screen back in the day to do SWIR imaging at 1550nm or so. You may see my old experiments back here:

 

[Foxfire]

Thanks Andy Perrin, Great info! Looks like i've still much to discover in UVP. This anti-Stokes SWIR imager is a Wow! I have an impression that the IR region between about 1 - 5 μm (NIR and Thermal) is the most interesting part of IR. 
Recently i read about anti-Stokes effect but it seemed that the materials that can do it are kind of rare. I wonder what is the material the upconverting “fluorescent” screen is made of? 

 

About X-rays that once i searched for x-ray cameras, also found some portable dentist x-ray machines on sale. Some were with manageable prices, but i didn't buy. It's a dangerous and therefor inconvenient thing to have. In case of high energy radiation i would better try to use that what's in a natural background, if this works at all, with some ultra long exposures, for introduction.

[Stefano]

As for X-rays, a professor mentioned that our university has an X-ray source which is used for teaching purposes as I understand (for radiation detectors). I would love to try it one day, not on myself but on objects, and doing it safely. Maybe you need to wear a dosimeter and/or follow a safety training to be allowed to use it. For high power lasers it's similar (you need to wear goggles and follow safety measures).

 

I would play with X-rays all day if only they weren't dangerous, like seeing your bones must be cool, but it's not worth the increased cancer risk.

[Andy Perrin]

You can’t use background radiation for imaging I don’t think? The sun barely makes any x-rays at all. The Planck distribution goes down exponentially in the tails, and even in UV you hardly get any light. There may be x-rays in the environment from other sources but usually not enough to image with. (An exception is peeling Scotch tape — apparently triboluminescence generates significant x-rays.) Old cathode ray tube TVs also allegedly made some, but we don’t have many of those left either. 
 

The most practical route is definitely dental equipment (and one person on here had an ancient postal x-ray machine). But the safety issues are so obvious and nasty that it’s probably best left unexplored. 
 

The SWIR and MWIR on the other hand are both safe and fascinating. I own a MWIR camera but it is so heavy I haven’t used it much. It weighs 15kg. My SWIR camera is the TriWave and I keep wanting to do more with it but my job doesn’t leave me enough time to play with my toys. 
 

I gave up on the fluorescent screen for SWIR because it required light that was far too intense - 600W halogen almost setting the objects to be imaged on fire! The TriWave was $3000 on ebay so I was very lucky. The current deals on ebay would let you get a SWIR InGaAs imager for $4000 I saw last night. 

[Foxfire]

Yes, the method that ulf suggested does really work! I was able to take some blurry images with one strongly fluorescent old soviet filter, (somekind of UV-1^x filter that i got with Kiev 6c). Possibly the image sharpness can be improved with better focusing and optimizing the lenses-adapters-macrotubes setup. But i post here one of my initial images, it's a corner of a Kodak Ultramax film packaging. 

 

So, in a sequence the setup was about like this: Baader U filter, UV transmitting lens, some macrotubes, old soviet fluorescent UV-1^x filter, Zeiss T* UV Filter, a lens (Sigma 28 mm F1.8), one more macrotube and a camera.

 

Lightsource: UV Beast 365 nm
 
It's kind of like old TV-s work, but here you go, the image appeared upside down (max high ISO 25600, exposure time 3 sec)

 

Edit: I would have placed macrotubes between the fluorescent + Zeiss *T UV filter and a Sigma 28 mm F1.8 lens, to get the "screen" further away from a lens, but i didn't had adapters 

[colinbm]

Just amazing.

 

[ulf]

Glad to see that the setup I dreamed up worked so good. 

Well done!

 

The UV beast is rather powerful so it will be more challenging with other light sources in UV-B or UV-C.

The method will never give really sharp images due to the glass depth but might with some luck be improved a bit.

 

As there never will be good sharpness due to the light conversion method I think a simple fused silica lens would be enough if you do not own a UV-Nikkor.

A one element FS lens has a bit better transmission than the UV-Nikkor's ca 70%.

 

It would be interesting to know if that Lumilass glass can be bought and if it is expensive.

[Foxfire]

3 hours ago, ulf said:

It would be interesting to know if that Lumilass glass can be bought and if it is expensive.

Yes, i would like to know also. Maybe i'll try to contact them in near future, but for example Edmund optics is offering something similar, min sensitivity of 1 µW/cm2 for emission, for 365nm peak. These are not so cheap. 

Found a paper discussing one of this Lumilass glasses (G9, green). It turns out this can be exited even with 157nm UV. 
The article is over 10 y old: Beam characterization and spatial coherence measurement of F2laserusing Lumilass glass fluorescence , but there are some more papers discussing Lumilass.

 

Probably the image sharpness depends on thikness of similar fluo-glasses. But yea, that's so cool that such glasses can be used at all in this way, i like it. Now i think i will try some random fluorescent plastics and other things.  

 

 

[colinbm]

@ulf @Foxfire Is this what you are describing ?
The link says the site is insecure ? My antivirus didn't shut it down.
http://www.davidhazy.org/andpph/text-reflected-uv.html

[ulf]

Yes Col, the basic setup is the same in the article as in Sirchie imagers and what I suggested.

The difference is that Foxfire is using a fluorescing glass material instead of a fluorescing surface to test if the Lumilass glass material could be used for this.

  

 

[Lou Jost]

I suspect that flourescent glass is not a good way to do this; because of its thickness it can't produce sharp points.  A thin coating of phosphors would be much better, but even there, the grain size of common phosphors could limit resolution...

[ulf]

10 hours ago, Lou Jost said:

I suspect that flourescent glass is not a good way to do this; because of its thickness it can't produce sharp points.  A thin coating of phosphors would be much better, but even there, the grain size of common phosphors could limit resolution...

You are quite right about that.

However, this thread was about exploring if fluorescent glass had any potential to produce images, not finding the perfect imaging solution for that.

 

Do you have any suggestion and sources for suitable  "common phosphors" and methods to apply a thin coating of it on a glass substrate?

What is the typical grain size of such materials?

 

I think short wave fluorescing materials are less common. Are they not?

[colinbm]

The UVB 310nm Fluorescent tubes have a white phosphor coating, which must be activated by 254nm - 310nm light ?
But getting some & applying a thin coating on a fused silica/quartz screen, I haven't found any yet.

[Lou Jost]

1 hour ago, ulf said:

You are quite right about that.

However, this thread was about exploring if fluorescent glass had any potential to produce images, not finding the perfect imaging solution for that.

 

Do you have any suggestion and sources for suitable  "common phosphors" and methods to apply a thin coating of it on a glass substrate?

What is the typical grain size of such materials?

 

I think short wave fluorescing materials are less common. Are they not?

 

Yes, it's cool that it is even possible with glass.

 

One easy source for fluorescent dyes and particles is MaxMax, and for some of their powders, the label gives particle size (10microns for some):

https://maxmax.com/shopper/category/9483-uv-powders

 

Here's one with really small 5 micron particles.

https://maxmax.com/shopper/product/15407-uvswb-5-grams-ultraviolet-shortwave-blue-fluorescing-powder/category_pathway-9483

 

I was planning on making a chamber and blowing a cloud of powder into the chamber, letting the powder settle onto the glass.

[Lou Jost]

51 minutes ago, colinbm said:

The UVB 310nm Fluorescent tubes have a white phosphor coating, which must be activated by 254nm - 310nm light ?
But getting some & applying a thin coating on a fused silica/quartz screen, I haven't found any yet.

Colin, I'm not sure I understand this. Wouldn't a 310nm lamp EMIT 310nm light? If so, it would have to be excited by a shorter wavelength (254nm?).

[ulf]

Interesting. Then you need some uv-transparent binder to make the powder stick to the glass surface.

It would be cool to do that directly on a de-beyered sensor with big pixels.

Then you could bypass the second focussing lens and make a more simple optical system

[Lou Jost]

42 minutes ago, ulf said:

Interesting. Then you need some uv-transparent binder to make the powder stick to the glass surface.

It would be cool to do that directly on a de-beyered sensor with big pixels.

Then you could bypass the second focussing lens and make a more simple optical system

Yes, that would be a great idea!