Don’t know about the circles but I always replaced the glass with the filter.
Yeah, when 2 pieces of glass get close enough that there’s a very small air-gap, you get funky optical properties. Some places would be in contact, some places would have a clear air-gap, others would be in that twilight zone in-between where it’d essentially be a vacuum (ie, other than maybe H2, no molecules would be able to fit.
So what you’re seeing is a sort of standing-wave of the 2 distinctly different interfaces: glass–glass, glass–air, and glass–vacuum, and the different refractive funkiness of each zone.
That’s why I don’t even like to keep the original glass when refitting with a TIR. Weird things can happen.
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Oh, wait a sec… you mean just the nekkid ZWB2 filter and no other glass on/under it? Hmm, never really noticed that. Will have to look. 
^ ah, now I see what rings were meant (they are called Newton rings, an interference effect between layers close to each other, close to parallel but not exact.)
Ah, good. I was hoping someone’d remember what they were called. I was drawing a blank.
Learned something new today. Yes, Newton rings are indeed what I’m seeing.
Thus by placing 2 pieces of glass (the non-AR-coated glass lens and the ZWB2 filter) close together, there is indeed an air-gap between them that causes these Newton rings… I wonder which one is the slightly convex curved glass — the plain glass lens or the ZWB2 filter — more likely the ZWB2 filter?
Is the coated version still available somewhere?
I do not understand, the coated version of what do you mean? (ZWB2 filters as far as I know are not coated).
There was a coated version mentioned above but I don’t know if it was released.
Ah sorry, I see, I should have read some posts back, the discussion is from last year and apparently I’m so senile already that I totally forgot.
I guess Simon never went on with it and pirate stopped bugging him about it. It is not in his store at least.
Ah that’s sad. The coated version would have been an even better addition than the non coated filter I think.
Just reread this post - forgot to update -sorry. Upon further investigation I was told that AR coatings are not really efficient for UVA and result in a significant transmission loss, so I just dropped it (sadly don’t remember the details). Of course I’m sure there are specialty houses which can create very efficient coatings, but at a very inefficient price (I was quote a couple hundred for one piece, and a setup charge as I remember).
Thanks for the research! Sometimes we gain nothing by investigating things, sometimes we find very useful stuff.
Thank you for the update.
Been looking on aliexpress and there is a bunch of sellers of the stuff there.
Is this glass required for an LG3535LED? I bought it assuming it was much better than a chinese brand in regards to the visible light output.
Specs on the LED are 380-385nm, but i see other sellers selling it under different wavelenghts and I question whether or not hose ones are genuine.
I cant find any datasheet from LG either.
The filter is for eliminating visible light. The Nichias emit the least with others emitting somewhat more. The cheap ones are the worst. You will enjoy the light more if you get the inexpensive filter. ,
i found them to work but they are very susceptible to breaking and chipping
i think the glass is soft, somehow
wle
Judging by the various price ranges for ZWB2 filters, i assume they’re not all the same quality.
true, and quality may not be entirely defined by glass hardness, either
mine were certainly cheap
wle
Yes im aware of that, I was trying to work out if the LG3535 puts out excessive visible light compared to the cheap chinese LEDs on the market.
Im wanting to use it on uranium glass most of the time and the odd time to cure UV resin.
i’m a uranium glass guy
i have found one hack for that, for testing it in the field, a cheap purple laser has tons of UV
you can even use it in day light
which no flashlight alone can overcome
lights it right up
wle