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UltravioletPhotography

[SAFETY WARNING] UVC video on YouTube


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Andy Perrin
Stefano that’s the same lens and image intensifier that Jonathan, David and I bought awhile back!
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I actually did wonder one moment if it was the same, but I didn’t check. Well, that’s even better. This shows what it can do.
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Yep pretty poor imaging off a focusing screen. The pi monochrome is much better.

Even my Em5mk2 in high resolution mode is fun.

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Actually the amazing bits from that imager is the filter and the lens. My filter is extremely excellent at UVC and fully blocked into uvA, visible and IR.

The other amazing thing is that 60mm lens. It has almost no focus shift at 254nm and visible, but ton in uvA, uvb and ir. I don't know how they did that. Also mine doesn't hotspot at 254nm. My UAT does at 254nm. So it works better for UVC imaging.

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Andy Perrin

Actually this is really cool. Took me a second to figure out what is going on:

Now there's something nobody has played with very much here: phosphorescence. (Credit to Stefano showing you can deactivate phosphorescence with red light, but aside from that I don't recall any other discussion here.)

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The videos I think tell the story. Only one in UVC, total nothing else.

Two UV induced fluorescent with these night vision systems.

And a whole bunch in SWIR and NIR.

 

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Now there's something nobody has played with very much here: phosphorescence. (Credit to Stefano showing you can deactivate phosphorescence with red light, but aside from that I don't recall any other discussion here.)

I don't remember where I discovered this effect (by "discovered" I mean read somewhere), but I think I already knew it when this video came out:

 

In fact I remember that when he talked about it at ~7:34, saying "Here's an effect I can't quite explain" I was like "I know the explanation!". Someone of course explained it in the comments.

 

He got that 375 nm UV laser for $80 on eBay. As he said, Thorlabs charges $4300 for one of them. It's here if you want to look at it: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=5400

 

On eBay doing a quick search you can find this: https://www.ebay.com/itm/154079947629. Less powerful than Thorlabs laser (16 mW vs. 70 mW), but it still should contain an actual UV laser diode. If someone ever thinks to buy it, please take it with a grain of salt. I'm not saying there is surely a working laser inside, but there is the possibility.

 


I still have to experiment with phosphorescence and SWIR. If SWIR light can "erase" it, then you can build a SWIR camera, but it won't be very efficient and the image quality is probably going to be very poor. But it will work. Maybe someone will try this before me and show us.

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Well its possible most of what we call UVIIRF is actually phosphorescence.

These Aurora cameras are just CMOS sensors and the company website only claims up tp 1100nm. So your not really seeing much SWIR with these. They are 0.9 Mpixel, so you get some sensitivity in the dark.

I think my monochrome Pi HQ sensor might be better. Or my Lodestar camera. If only a better software interface existed for the Lodestar. than it would really be a useful camera.

 

What really sells these Aurora cameras is they are almost military grade and can handle the recoil from a weapon, thus easily mounted on your AR of choice for full personal protection. Yes I watched too many reviews. I may now get some Guns and Ammo ads.

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Andy Perrin

“ Well its possible most of what we call UVIIRF is actually phosphorescence. ”

That doesn’t make much sense to me. The distinction between fluorescence and phosphorescence is the time it takes for the light to decay after you switch the UV off. I’ve never noticed the UVIIRF hanging around much after shutting off the light?

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Andy Perrin
What they are calling SWIR seems to be just 1100nm stuff. I asked the guy, he said it wasn’t like InGaAs range.
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Andy Perrin
Yes, it’s still just silicon. In fact, from watching other videos on that Aurora, it seems to be not much more sensitive than my A7S.
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  • 1 year later...
Daniel Csati

That's the black silicon company.. They microstucture the surface to increase absorption. Actually it does have some response up to 1500nm, probably <1% QE so they have to use huge gain to get the image information out.

https://en.m.wikipedia.org/wiki/Black_silicon

Unfortunately the technology is limited by pixel size so we won't see much higher resolution in the near future

 

Fig1-Responsivity.jpg

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Andy Perrin

Maybe that graph is true in some theoretical sense, but I remember asking the guy who had one and he didn’t think it reached very deeply into SWIR with his actual device. This was awhile ago though, and I don’t know if newer devices have further reach. 
 

By the way, in the depths of the wiki article you linked, they mention that the “black silicon” has sulfur doping, so…it’s not “just silicon” as I supposed in the original comment above. This accounts for some of the SWIR absorption because the sulphur modifies the bandgap. 

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Daniel Csati

Sure, it's definitely not very useful for SWIR-only imaging. I wonder how it would work with a 1300nm long pass filter in the night using the light from the nightglow.

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Andy Perrin

It looks like the “knee” in the chart is right at 1300nm, so my guess would be that it would work poorly. I have never actually seen the nightglow even with my TriWave simply because I live in a city and the light pollution is much stronger than nightglow. 

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