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UV first attempt

 
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kit1980



Joined: 18 Aug 2016
Posts: 99
Location: Bellevue, WA, USA

PostPosted: Fri May 19, 2017 9:22 am    Post subject: UV first attempt Reply with quote

So I've got my UV source. The LEDs claim to be 365nm, but there are significant visible light leaks. I've ordered ZWB2 filters, but shipping from China will take some time.

Also it looks like the camera picks up some reflected UV light - purple color is the picture is invisible through the oculars.



The object is a laundry detergent grain, 10x objective, stack of 40+ photos.
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houstontx



Joined: 31 Jul 2015
Posts: 159

PostPosted: Fri May 19, 2017 9:41 am    Post subject: Reply with quote

I too put the zwb2 filters on the led lights and it seemed to cut the visible light by about half, but not fully...Any little bit helps I guess...you get what you pay for Smile
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Pau
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Joined: 20 Jan 2010
Posts: 3691
Location: Valencia, Spain

PostPosted: Fri May 19, 2017 11:57 am    Post subject: Reply with quote

Kit, Please, tell (or refresh) us the equipment used: UV LED source and filters used.

The image is surprising for me because several wash machine detergents I've tested produce a very strong blueish white fluorescence emission and what I see is mostly violet and purple, like if the image was showing more the visible reflected emission light than the actual fluorescence (the blue points). Maybe, as you suspect, there is UV reaching the sensor (and eyes!) and the camera shows it as violet.
Do you use any emission filter to cut UV and violet before reaching the sensor/eyepieces?

houstontx, my cheap zwb2 filters mounted on the Convoy S2 Nichia UV torches cut off most violet emission, there is some still remaining but much less than 50%, 10% maximum I would say without actually measuring it.
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Last edited by Pau on Fri May 19, 2017 2:23 pm; edited 1 time in total
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kit1980



Joined: 18 Aug 2016
Posts: 99
Location: Bellevue, WA, USA

PostPosted: Fri May 19, 2017 12:50 pm    Post subject: Reply with quote

Pau wrote:
Kit, Please, tell (or refresh) us the equipment used: UV LED source and filters used.

The image is surprising for me because several wash machine detergents I've tested produce a very strong blueish white fluorescence emission and what I see is mostly violet and purple, like if the image was showing more the visible reflected emission light than the actual fluorescence (the blue points). Maybe, as you suspect, there is UV reaching the sensor (and eyes!) and the camera shows it as violet.
Do you use any emission filter to cut UV and violet before reaching the sensor/eyepieces?


I used AmScope illuminator https://www.amazon.com/AmScope-Powerful-Goose-neck-UV-365-Illuminator/dp/B01I48BCXS/ref=sr_1_8?ie=UTF8&qid=1495222880&sr=8-8

I didn't use any emission filters (but I wore UV-resistant prescription glasses plus UV-safety goggles on top of them). Most of the violet is from visible violet light from LEDs, the thing that camera sees but not eyes is more reddish-purple stuff. I tried using my old unused "UV" camera filter, but it turned out that the filter doesn't filter UV at all.
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Charles Krebs



Joined: 01 Aug 2006
Posts: 5638
Location: Issaquah, WA USA

PostPosted: Fri May 19, 2017 2:16 pm    Post subject: Reply with quote

You really should filter the LED UV lights and also have an "emission" filter.

You could use a Tiffen Haze 2A ( https://tiffen.com/protection-uv-control/ ) for a readily available and low priced emission filter (most camera "UV" filters are inadequate). Tiffen purchased the "Wratten" filter business from Kodak, and you could also use a Wratten 2A or 2E gel. These are much more delicate but can be easily cut to size and are optically good.

Even the best UV LEDs have some spillover into visible violet/blue. Some are much worse than others. The ZWB2 filters you have ordered should be adequate. You can also search around for filters made of Hoya U360 or Schott UG11 glass.
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Charles Krebs



Joined: 01 Aug 2006
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Location: Issaquah, WA USA

PostPosted: Fri May 19, 2017 2:40 pm    Post subject: Reply with quote

kit1980 wrote:
the thing that camera sees but not eyes is more reddish-purple stuff.


Check your separate RBG channel histograms. It is really easy in a case like this to "blow out" the blue channel and then the resulting recorded image really becomes "reddish-purple".
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Pau
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Joined: 20 Jan 2010
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Location: Valencia, Spain

PostPosted: Fri May 19, 2017 2:50 pm    Post subject: Reply with quote

I agree, you do need an adequate emission filter. Very likely you could just drop it inside the microscope body under the trinocular head (first check if there is enough room for it)
Omega, one of the main microscope filter makers has an outlet ebay store with low prices, I've bought some of my filters from them:
http://stores.ebay.com/OmegaFiltersEbuyer2/_i.html?_fsub=305264011&_sc=1&_sop=1

This one would be fully adequate but it is very small:
http://www.ebay.com/itm/Optical-Longpass-Filter-420LP-12-7-x-2mm-thick-EB00107B-/311651257558?hash=item488fdcccd6

This one also will do but because it lets to pass all visible you need an excitation filter able to cut off all violet:
http://www.ebay.com/itm/Optical-Filter-400CFLP-25mm-diameter-X-1-5mm-thick-EB00086B-/160554349065?hash=item2561c8f209

If a 18mm diameter round filter can fit, I have some surplus ones (I bought two sets and only need one)
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kit1980



Joined: 18 Aug 2016
Posts: 99
Location: Bellevue, WA, USA

PostPosted: Fri May 19, 2017 3:45 pm    Post subject: Reply with quote

Thanks Charles and Pau, I'll order couple more filters for experimenting and also that Convoy flashlight to compare with AmScope's LEDs.

Pau wrote:
This one would be fully adequate but it is very small:
http://www.ebay.com/itm/Optical-Longpass-Filter-420LP-12-7-x-2mm-thick-EB00107B-/311651257558?hash=item488fdcccd6

Interesting, so it also removes some visible violet. This should work good as long as nothing actually has violet fluorescence...
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WalterD



Joined: 06 Jul 2015
Posts: 218
Location: Rotterdam, the Netherlands

PostPosted: Tue May 23, 2017 8:32 am    Post subject: Reply with quote

Very interesting Kit, did you have time to experiment with other objects? Just curious Smile
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kit1980



Joined: 18 Aug 2016
Posts: 99
Location: Bellevue, WA, USA

PostPosted: Tue May 23, 2017 9:52 am    Post subject: Reply with quote

WalterD wrote:
Very interesting Kit, did you have time to experiment with other objects? Just curious Smile

Thanks! Not yet, I'm waiting for some filters.
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