Reasonably clean UV-C set-up

[Lou Jost]

Warning: UV-C is dangerous and eye and skin protection is needed!

 

I now have a decent set-up for reflected UV-C macro photography (this will also work for fluorescence of course). I found a good eBay deal on a MaxMax 8Mp monochrome camera with a naked sensor, no coverglass. It came with a quartz lens. I bought an Edmund Optics Techspec 254nm filter, with 40nm FWHM, for the lens. It claims blockage >OD4 for off-peak wavelengths through far infrared. I used a cheap $20 6W germicidal lamp as a light source. I think this emits 254nm, 311-313nm, 365nm and maybe small amounts of other wavelengths.

 

Everything worked perfectly with no complications. My test set-up uses a PTFE-wrapped background, white and non-fluorescent. The subjects were two glass objects with some aluminum foil in them.

 

Here are the results. The left photo is under white visible light, no filters. Photo 2 is under the germicidal lamp with a 365nm filter on the lens. Note the lettering on the beaker is black! The glass blocks just a very little of the UV at this wavelength. Photo 3 is under the germicidal lamp with a 300nm filter (50nm FWHM) on the lens. Note that the glass is absorbing lots of UV but is not completely opaque at this wavelength; you can see the aluminum foil inside the left glass. Photo 4 is under the germicidal lamp with the Edmund Optics 254nm filter (40nm FWHM). Now the glass is completely opaque. Exposure was 1/2s, f/4. The blackness of the glass tells me there is no photographically significant IR leakage.

 

 

[colinbm]

Fantastic Lou
What is the camera please ?
How do you clean the sensor ?

[Stefano]

Very nice!

[Lou Jost]

9 hours ago, colinbm said:

Fantastic Lou
What is the camera please ?
How do you clean the sensor ?

Thanks Colin,  it is a MaxMax camera similar to this one:

https://maxmax.com/shopper/product/15982-xniteusb8m-bcm-usb-2-0-8-megapixel-monchrome-camera-module/category_pathway-9490

but not exactly the same. I have seen mine on their website previously but it is not there now. Mine has a c mount. I have modified it to take other lenses as well.

 

I use air (very carefully) to clean the sensor, and I try not to get it dirty!!

 

4 hours ago, Stefano said:

Very nice!

Thanks Stefano

[colinbm]

Thanks Lou
It looks like it has some potential.

[Andy Perrin]

Nice. What do you plan to photograph?

[Lou Jost]

23 minutes ago, Andy Perrin said:

Nice. What do you plan to photograph?

 

This is just Step 1; the goal is to do UV-C microphotography of potentially new species of terrestrial diatoms, since scanning electron microscopy is not easily available here.

 

Diatoms are basically made of glass. Taking photos of transparent things like diatoms is hard. But in UV-C diatoms are not transparent any more. And the resolution advantage over visible light is significant.

[Andy Perrin]

You can keep Jonathan company with the diatoms. Looking forward to the images. 

[Lou Jost]

8 minutes ago, Andy Perrin said:

You can keep Jonathan company with the diatoms. Looking forward to the images. 

Yep, he is my inspiration.

[lukaszgryglicki]

Wow! Great photos, I love them.

 

[JMC]

Nicely done Lou. If it's of interest, here's my initial work using 254nm - https://jmcscientificconsulting.com/uvc-photography-at-254nm-into-the-darkness/

[Lou Jost]

9 hours ago, lukaszgryglicki said:

Wow! Great photos, I love them.

 

Thanks Lukasz!

 

5 hours ago, JMC said:

Nicely done Lou. If it's of interest, here's my initial work using 254nm - https://jmcscientificconsulting.com/uvc-photography-at-254nm-into-the-darkness/

I've read your entire blog several times, and I think it is the best discussion of UV-C photography on the internet. Other people who want to learn about this should definitely explore your blog first!

[JMC]

On 10/16/2023 at 3:07 PM, Lou Jost said:

I've read your entire blog several times, and I think it is the best discussion of UV-C photography on the internet. Other people who want to learn about this should definitely explore your blog first!

Thank you Lou, that's very kind. I hope to get some time to do some more UVC work and update it soon. I've got a 30w deuterium light source, which I hope to use in combination with an Asahi XUV0310 filter and my UV sensitive machine vision camera for some UVC/B microscopy. While not true monochrome 254nm (as it'll be a range of light from 250 to 310nm) it should make for some interesting images. Just.....need.....to.....find......the......time.......to........experiment.

[lukaszgryglicki]

Actually a light source from 250 to 310 would be ideal, the biggest problem (for me) is to block everything else - as it always dominate.

 

[colinbm]

@JMC Good luck with the Deuterium light.
I have acquired one too, 30w Deuterium, but I am far from impressed with it.
The 4w 254nm Mercury vapour lamps are superior at Fluorescing Minerals.

[Lou Jost]

2 hours ago, lukaszgryglicki said:

Actually a light source from 250 to 310 would be ideal, the biggest problem (for me) is to block everything else - as it always dominate.

 

I initially thought this also. But it depends very much on your lens or objective. A pure quartz lens or microscope objective (the only reasonably-priced UV lenses on eBay) has too large a focus shift between different "colors" of UV. Sharper photos will be obtained with a more narrow bandwidth. On the other hand a combination quartz and calcium flouride lens like the very expensive well-known UV lenses, or a purely reflective lens, can probably handle that wavelength range.

[Lou Jost]

2 hours ago, lukaszgryglicki said:

Actually a light source from 250 to 310 would be ideal, the biggest problem (for me) is to block everything else - as it always dominate.

 

I think the most interesting part of my result is that at 254nm there was no problem with non-target light dominating, even though I just used a single filter.

[Andy Perrin]

Lou, you probably should verify that further. I mean you made a good case for it, but one test of anything is not as good as two independent tests...

[Lou Jost]

7 minutes ago, Andy Perrin said:

Lou, you probably should verify that further. I mean you made a good case for it, but one test of anything is not as good as two independent tests...

I'm open to suggestions for an additional test. Any ideas?

 

It seems to me that the the blackness of the glass relative to the non-fluorescing light gray background, and its opacity (the aluminum foil strip in the left glass is not visible at all in the 254nm photo, while it is visible in the 300nm photo), are pretty good evidence that there is no significant IR or vis or 365nm leakage. There surely is some tiny leakage, but it seems not to be photographically significant, and certainly not dominant, with this naked-sensor camera.

[lukaszgryglicki]

In my case the lens is not an issue - I have both quartz only (UV5035BK2) and UV-Nikkor (quartz and fluorite).

 

[Lou Jost]

25 minutes ago, lukaszgryglicki said:

In my case the lens is not an issue - I have both quartz only (UV5035BK2) and UV-Nikkor (quartz and fluorite).

 

Yes, I think I remember seeing your posts with the UV Nikkor. I don't have the funds for that. Though I am always searching for some forgotten or mislabeled one on eBay...

[JMC]

Few thoughts.

 

Lou - when I did my UVC test I tried it in combination with a WG305 filter (and also tried a WG295 one) the aim being to block as much as possible from above 300nm. It's difficult without seeing all the transmission spectra of the different filters to be 100% sure about everything that is going on. My gut feel is that you are getting mainly UVC, but I always like to see data to back up my feelings.

 

Col - the deuterium lamp will be less intense than the 254nm low pressure mercury lamp. But it will have a much broader emission range. This is why I think trying it with a XUV0310 filter is where I will start as this has a nice broad transmission profile. I'll be using it in combination with a condenser lens to try and get a parallel beam. Also I'll be using my UV camera with the Sony UV sensor to give me the best sensitivity. What would be ideal is a focusable 254nm low pressure mercury lamp which is small enough to get into the microscope lamp port, but so far I have not found anything suitable. All in all not a trivial task.

[colinbm]

Thanks Jonathan
As always I will be looking forwards to seeing your results.

[JMC]

3 minutes ago, colinbm said:

Thanks Jonathan
As always I will be looking forwards to seeing your results.

No problem Col. I cannot promise anything soon, but when i have something to share I will.

[JMC]

15 hours ago, Lou Jost said:

I initially thought this also. But it depends very much on your lens or objective. A pure quartz lens or microscope objective (the only reasonably-priced UV lenses on eBay) has too large a focus shift between different "colors" of UV. Sharper photos will be obtained with a more narrow bandwidth. On the other hand a combination quartz and calcium flouride lens like the very expensive well-known UV lenses, or a purely reflective lens, can probably handle that wavelength range.

That is a good point. I noticed some focus shift in the UV with my Ultrafluars, BUT, my photoeyepiece was a Lomo one which may well be just quartz. It could have been this rather than the Ultrafluars which gave to focus shift. I have yet to track down an Ultrafluar photoeyepiece. Apparently they exist but they seem to be extremely rare. I do have a Leitz UV photoeyepiece which was either a one off or a prototype as I cannot find anything at all on this, even whether or not it should exist. The plan is to use this with the Leitz UV lenses, but I need to work out the right distance between it and the camera before I can do that. More things to add to the list of jobs.......