I’m trying to explore fluorescence of materials using UV light. It’s also a part of UV demonstration for students.
The UV lights that I’ve seen emit fairly wide spectrum, ‘leaking’ blue part of spectrum as well. This confuses students as the UV was supposed to be invisible.
Is there a commercial flashlight that would perhaps use a combination of a proper UV LED an a filter to minimise the emissions in the visible range?
365nm led with appropriate filter will (mostly) do what you want, when Chinese New Year is over, you could order a Convoy S2+ UV.
Not sure how you demonstrate UV is invisible, cant stare into the beam for safety reasons, and lots of white surfaces have whiteners in them which flouresce.
Perhaps a whiteboard or white wall might not show strong fluorescence; with the lights on/dim, any stray light won’t be visible, if you taped an A4 sheet of paper on the wall, the blue fluroescence would be very visible. Highlighters pop particularly nicely.
“Invisible” UV ink could also be a good example, as can the UV security features on banknotes.
Edit to add: there’s a bulls*** controversial patent on visible light filters on flashlights, so you might have to buy the Convoy S2+ with UV LED and the filter separately (both available from Simon when his store is not on holiday). It’s easy to unscrew the head* and fit the filter.
*For clarity: you unscrew the head then with fine pliers or tweezers, then back the pill out of the head, pop the glass lens out, put the ZWB2 in, then screw the pill back in, then screw head back on. It’s still pretty straightforward when you’ve got the light in-hand.
Cheers! How wide of a spectrum would a 365 nm LED without a filter have? Is there a graph showing it somewhere?
The filters are mainly sold under the ‘ZWB2’ denomination by the way. (If you want to search for it on Aliexpress for example.)
Depends on which LED is currently being used, I’m not sure the current emitter being used.
SBT-10X 365nm (which is weird as 365nm version only listed in the bin table and not the part numbers table) states 370nm is the longest wavelength. Mine had slightly blue hue so either i got one that was longer wavelength, or the LED emits a tiny bit of blue, or my eyes can see 370nm…
NCSU276C (365nm) Might be the current S2+ UV LED used, as per a Zero air review. This has a peak wavelength of 365nm, and a spectrum half width of 9nm, so likely similar to the SBT-10X albeit less powerful.
The Lumintop Tool AA-UV comes with the filter already installed.
https://www.amazon.com/dp/B08ZY67T5Y/
The Sofirn SF16-UV also comes with the filter installed.
https://www.amazon.com/dp/B0CMQCJYFT/
Get both. You’ll thank me later.
From Wikipedia on Visible Spectrum:
A typical human eye will respond to wavelengths from about 380 to about 750 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 400–790 terahertz. These boundaries are not sharply defined and may vary per individual. Under optimal conditions these limits of human perception can extend to 310 nm (ultraviolet) and 1100 nm (near infrared).
I always thought it was narrower than that.
Cool info, the most probable explanation is the small amount of light emitted at wavelengths other than peak, these are narrow but not true monochromatic emitters. It’s highly plausible my LED has some 390nm+ emission, though it’s a small amount of total.
I remember reading a blog post about 10 years ago about a guy who’d had surgery (cateracts removed?) and could now see more of the deep blue part of the spectrum. Absolutely no way I can find it now, it’s in the depths of the internet!
Convoy flashlight store sell both uv flashlights and the filters.
On Amazon the Alonefire and UvBeast lights have zwb2 filters already installed to block visible light. The alonefire lights are cheap and work okay. Not very durable, but it worked for finding sodalites for a while. The leluohq uv light on Amazon is like $15 without a battery. Its an 18650 light and has the black zwb2 filter.
Separately.
I’ve heard Simon won’t even stick the filter and light in the same order, let alone package, as to not run afoul of the “patent”.
And you’d still need tools to pull out the pill, swap glass for filter, and reassemble. Hope ya got ring-pullers, or are willing to grind down some needlenose pliers, etc.
Oh, and if you got a pill that’s soldered in vs a ring, well, rotsa ruck.
I did that, stuck everything into a purple host, but I had all the shiite to do it. A n00b might not.
He did for me, but that was an order to EU… AFAIK that stupid patent is only valid in US. I still had to put it in the light myself.
There was a Sofirn deal recently with the filter.
Welllll…I don’t want to get anybody in trouble…sooo…ya, that’s exactly what he does. Mine had a regular lens installed when it showed up, not the filter.
What’s the patent about exactly?
Idiots wanted to patent the idea of sticking a filter in front of a light-source to change the spectral output.
Bigger idiots in the USPTO thought that was unique and novel and nonintuitive as to actually grant the patent.
IIRC, someone correct me if I’m wrong, it’s a patent on putting a UV pass filter on a UV flashlight.
True and I recently found out laundry detergents do something similar with “optical brighteners” to trick our eyes into thinking it’s making our clothes cleaner or colors brighter.
You can see it if you put a brand new piece of clothing you just bought that’s never been washed next to a similar piece that’s gone through the laundry a few times and shine a UV on each of them. The one that’s gone through the wash is blinding compared to the new one.
Works better if both pieces don’t have any white threads. They must be whitened at the factory like paper is or something idk
Yeh the exact wording is something stupid like converting unwanted wavelengths into other wavelengths. There’s a BLF thread here.