UV to Visible Light Converters

[colinbm]

The last suggestion that I saw a year or more ago, but I haven't tried it, because I haven't got any phosphor that the 310nm fluorescent tubes use.
A equal mixture of Alcohol & Phosphoric Acid with the Phosphor powder to make a thin paste can be used to apply the Phosphor to the glass.
The Alcohol will evaporate with some of the Phosphoric Acid, leaving a sticky surface to adhere the Phosphor Powder.
 

[Foxfire]

Did some more testings and eventually was able to get relatively sharp images. Maybe i'm rushing with the conclusion (have to do more testing), but what seems to be is that when using fluorescing glass materials, there's some abberation-like thing happening - the image is sharper in the middle, but gets more blurred the further away from the center. I'm guessing it's something to do with refraction in the glass material, and the thicker the fluorescing material the more blurring at the sides. 

 

For some visuals i add here one image of a decorative pumpkin (leftover from Halloween time). I had to photograph it from about 2-3 meter distance, that seemed to lower the sharpness, also the long exposure (it's not the sharpest image i got, but i got it nicely into the frame). Surprising was the hologram-like effect. ISO 100, Exp time about 7 min

 

So yes, probably, in the sake of image sharpness, it would better to use thin fluorescent coatings (paints), or maybe the fluorescing glass material needs to be shaped as a lens.  

 

But what is exiting about this Sirchie imager style method is that it's possible to use all kinds of transparent or semi-transparent fluorescing materials as a screen. For example just a plastic from some plastic bottle or even a white paper that is quite fluorescent. 

[Lou Jost]

That's actually quite nice for this method!

[Foxfire]

Thanks Lou Jost! I think i'll try all sort of fluorescing materials from now on :)

[colinbm]

@Foxfire That is starting to look fancy.

[colinbm]

@Lou Jost Just found what I was looking for.
I have, in the past, tried to purchase some of this, but because I don't have a DHL account, they won't ship to me ??
If someone gets some I would like to see a piece please.

https://phosphortech.com/uv-phosphors/

[Lou Jost]

33 minutes ago, colinbm said:

@Lou Jost Just found what I was looking for.
I have, in the past, tried to purchase some of this, but because I don't have a DHL account, they won't ship to me ??
If someone gets some I would like to see a piece please.
https://phosphortech.com/products/phosphor-sheets/#

Very interesting. They say they can make those sheets as thin as 50 microns, which would help sharpness.

[ulf]

2 hours ago, Foxfire said:

Did some more testings and eventually was able to get relatively sharp images. Maybe i'm rushing with the conclusion (have to do more testing), but what seems to be is that when using fluorescing glass materials, there's some abberation-like thing happening - the image is sharper in the middle, but gets more blurred the further away from the center. I'm guessing it's something to do with refraction in the glass material, and the thicker the fluorescing material the more blurring at the sides. 

 

For some visuals i add here one image of a decorative pumpkin (leftover from Halloween time). I had to photograph it from about 2-3 meter distance, that seemed to lower the sharpness, also the long exposure (it's not the sharpest image i got, but i got it nicely into the frame). Surprising was the hologram-like effect. ISO 100, Exp time about 7 min

 

So yes, probably, in the sake of image sharpness, it would better to use thin fluorescent coatings (paints), or maybe the fluorescing glass material needs to be shaped as a lens.  

 

But what is exiting about this Sirchie imager style method is that it's possible to use all kinds of transparent or semi-transparent fluorescing materials as a screen. For example just a plastic from some plastic bottle or even a white paper that is quite fluorescent. 

Partly it could also be that your image projection and also the second lens's focal plane ara not completely flat. Normal photographic lenses are not always that, especially when fully open. 

Enlarger lenses are better for this and would hit the fluorescing surface more straight on.

What lens / lenses settings are you using in your setup? Camera type?
Is the last image a crop of a 100% or reduced resolution scaled?

 

 

[ulf]

1 hour ago, Lou Jost said:

Very interesting. They say they can make those sheets as thin as 50 microns, which would help sharpness.

I cannot find anything about 50 um or thta they cam make them for UV-C excited phosphors.

The link leads me to white emitting blue light excited materials for illumination. Are we looking at the same page?

[Lou Jost]

1 hour ago, ulf said:

I cannot find anything about 50 um or thta they cam make them for UV-C excited phosphors.

The link leads me to white emitting blue light excited materials for illumination. Are we looking at the same page?

There is a lot of material on their website. The 50um figure is there somewhere. There is only a brief mention of UV-C where they talk about down-conversion theoretically. I did not find any claims about their products being excited by UV-C but judging from the things they discuss, I would expect they do have UV-C sensitive products. Unlike transmission of UV-C, excitation by UV-C should be easier than by visible light, because it has more energy.

[DKoch]

On 11/17/2023 at 7:09 PM, Lou Jost said:

 

 

On 12/1/2023 at 8:10 PM, 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 

 

The glass looks like it's actually transparent, so you would need a phosphor or something at the focus plane anyways wouldn't you? This all reminds me of an incredibly simple setup i once saw at a Total Solar Eclipse: to observe the sun's disc in 392nm UV, they had painted a "screen" with a phosphor meant to fluoresce around this wavelength and inclosed it in a light tight box. Their telescope projected into it; it was a greenish yellow image...I guess what's great about a setup like this is you could have different dye "targets" for different wavelengths...of course light level was no issue as they were imaging the solar disc!

[ulf]

7 minutes ago, Lou Jost said:

There is a lot of material on their website. The 50um figure is there somewhere. There is only a brief mention of UV-C where they talk about down-conversion theoretically. I did not find any claims about their products being excited by UV-C but judging from the things they discuss, I would expect they do have UV-C sensitive products. Unlike transmission of UV-C, excitation by UV-C should be easier than by visible light, because it has more energy.

At least some minerals are excited by buy short wave UV only and some by long-wave UV only, despite that AW-UW have higher energy.

[ulf]

30 minutes ago, DKoch said:

The glass looks like it's actually transparent, so you would need a phosphor or something at the focus plane anyways wouldn't you?

No, it is the glass material only that Foxfire have used for his experiments to test the principle.

The reason it is possible to form an image that is somewhat sharp is that the UV-light energy is much higher with the projected image in focus. Outside that plane the energy is rather quickly diluted and will show much less fluorescence excited light.

 

I think the dynamic range will be rather low and the images will aways be marred by light outside the focal plane, but the principle will work. 

I also guess that a much higher ISO could be used for shorter exposure times, together with some good noise reduction software, as there will never be a really pixel-sharp image.

 

[Foxfire]

On 12/3/2023 at 4:56 PM, ulf said:

Partly it could also be that your image projection and also the second lens's focal plane ara not completely flat. Normal photographic lenses are not always that, especially when fully open. 

Enlarger lenses are better for this and would hit the fluorescing surface more straight on.

What lens / lenses settings are you using in your setup? Camera type?
Is the last image a crop of a 100% or reduced resolution scaled?

 

 

Yes, this picture of a pumpkin is a cropped and reduced size image. The center is about where it was, just a little bit on the left. It can be guessed by the faint circular halo that also appeared. 

 

for UV transmitting lens i'm using EL-Nikkor 80mm old metal type, at f/11, for photographing the fluorescent UV-1x filter i'm using Sigma HIGH SPEED WIDE AF 28mm f/1.8 at f/22. 

Camera: unmodified Nikon D5500

 

With two lenses the focusing is not very easy, it's actually a bit hard, so i used smaller apertures in hoping to get sharper images. 
 

On 12/3/2023 at 4:56 PM, ulf said:

Partly it could also be that your image projection and also the second lens's focal plane ara not completely flat.

Yes! it appears that the lens is the main reason for blurring. I checked it in the visible light and the distortion on the sides is caused by this Sigma lens, not by the fluorescent glass material! Later i used different lens and got better/sharper images, almost ok-sharp images. I will post some more results later.

[ulf]

22 minutes ago, Foxfire said:

Yes, this picture of a pumpkin is a cropped and reduced size image. The center is about where it was, just a little bit on the left. It can be guessed by the faint circular halo that also appeared. 

 

for UV transmitting lens i'm using EL-Nikkor 80mm old metal type, at f/11, for photographing the fluorescent UV-1x filter i'm using Sigma HIGH SPEED WIDE AF 28mm f/1.8 at f/22. 

 

With two lenses the focusing is not very easy, it's actually a bit hard, so i used smaller apertures in hoping to get sharper images. 
 

Yes! it appears that the lens is the main reason for blurring. I checked it in the visible light and the distortion on the sides is caused by this Sigma lens, not by the fluorescent glass material! Later i used different lens and got better/sharper images, almost ok-sharp images. I will post some more results later.

Excellent choice for the UV-transmitting lens!

 

That is exactly what I would have tried with, or possibly my EL-Nikkor 105mm.

A longer focal length will give more narrow angle projection beams hitting the filter and give a more even beam shape in center and corners.

The ideal focus setting off the input light would be at the front side of the filter.

(Might have said that before. If so sorry for parroting the obvious. ;-)

 

The secondary lens would better also be an enlarger lens as they are designed to have  flat focus fields at both sides, as normally both the negative and the photo papers are supposed to be flat.

For a reasonable build-length I would have used one of my Focotar 50mm.

As you already have stoped down the Sigma very much, a better suited lens with a more flat focal plane would allow you use it more open, maybe at f/8, and gain some exposure speed.

The Focotar is a very good lens, but here in this application I think a simpler enlarger lens would be good enough.

 

I am really looking forward to see your next progress in this setup.

[Foxfire]

A better setup: 
Baader U-Filter, EL-Nikkor 80mm, focusing helicoid, fluorescent screen, Zeiss *T UV filter, AF-P DX Nikkor 18-55mm f/3.5-5.6G VR lens, extention tubes, camera (unmodified Nikon D5500). 

 

On 12/4/2023 at 5:40 PM, ulf said:

The secondary lens would better also be an enlarger lens as they are designed to have  flat focus fields at both sides, as normally both the negative and the photo papers are supposed to be flat.

For a reasonable build-length I would have used one of my Focotar 50mm.

When i attempted to rearrange the setup to use EL-Nikkor 80mm as a lens that sees the Vis fluorescence image, i gave up because it seemed that EL-Nikkor 80mm would have needed too long tubing for focusing on the fluorescent screen. But i'll check the Focotar 50mm, or something in that direction., thanks for the mentioning and helpful comments in general!  And ofcourse, for everyone here thinking along!

 

With my current lenses/setup i think i reached about the limit of how sharp i can make it. But i think it's worth to continue to improve and optimize, and test different fluorescent materials. 

 

Here are some latest test results (unedited .jpg), pictures of a Baader U-Filter box and a metal ruler (lightsource: uvBeast V3)
Fluorescent filter: EL-nikkor 80mm at f/11, Nikkor 18-55mm at f/11, ISO 100, Exp time over 7min

 

Plastic from a water bottle: EL-nikkor 80mm at f/11, Nikkor 18-55mm at f/11, ISO 400, Exp time about 10 min

 

White paper,  EL-nikkor 80mm at f/16 (or f/11 - not sure), Nikkor 18-55mm at f/11, ISO 100, Exp time 30sec

 

And these are the screens in Vis and UViVisF. from left to right: fluorescent UV-1^x filter, plastic from a water bottle, white paper.  
White paper was the brightest, so it needed the shortest Exp time.

 

 

[Foxfire]

I tried also another kind of setup that worked like a 90° diagonal mirror lens that is used to produce a right-angle bend in a light path. So i assembled something like it, only that in place of a mirror i used white paper (as a fluorescent screen). One of the idea was to see how much it would differ if the image is UVifluo projected on to the screen material, compared to if the photograph is taken through the fluorescent screen material (as previously). It turns out it's much sharper.

 

Setup was very loosely built and produced a lot of distortions, only part of the image was sharp, and there were also a light leakages. From the images i got i'll post one better and edited version, for just to give a hint about the sharpness on paper, if looking on to the paper screen. This can be compared to an image in previous setup where it was looked through the paper screen.

 

EL-nikkor 80mm at f/11, Nikkor 18-55mm at f/11, ISO 100, Exp time over 10 min. I think i can see some texture of a paper in the sharper part.