• Ultraviolet Photography
  •  

309nm UVB LEDs

13 replies to this topic

#1 colinbm

    Member

  • Members+G
  • 2,741 posts
  • Location: Australia

Posted 12 July 2021 - 15:45

I have just assembled a 309nm LED light with 9 x 3w 309nm LEDs.
I will make a second light the same & use then for UVB fluorescence.
This is a visible light photo to show the setup & the consumption on a 12V DC battery.
It is fan cooled, barely gets warm.
What you see from the LEDs is the out of band light, it doesn't even register on the spectrometer, just a nice narrow spike at 309nm.

Attached Image: 2021 07 12, 9 x 3w 309nm LEDs.jpg

#2 Stefano

    Member

  • Members(+)
  • 2,173 posts
  • Location: Italy

Posted 12 July 2021 - 16:40

Pretty! Do you want to try UVB-reflected photography too?

#3 Fandyus

    František G.

  • Members
  • 229 posts
  • Location: Czech republic, Northern Bohemia

Posted 12 July 2021 - 18:21

I second what Stefano said, could be interesting.

#4 colinbm

    Member

  • Members+G
  • 2,741 posts
  • Location: Australia

Posted 12 July 2021 - 21:38

I will certainly try it out in the next day or two, but I have no expectations of success as my camera doesn't seem to go lower then 340nm, but I'll see what can be forced ?

#5 Stefano

    Member

  • Members(+)
  • 2,173 posts
  • Location: Italy

Posted 12 July 2021 - 21:58

If all you have on the sensor is the coverglass, then you may get that low. But unless someone measured the transmission of you camera model’s coverglass, we don’t know.

#6 colinbm

    Member

  • Members+G
  • 2,741 posts
  • Location: Australia

Posted 12 July 2021 - 23:47

I measured the output of the 309nm UVB LEDs at 25w output & at 300mm distance.

Attached Image: 20210713_25wUVB_309nmLED_at_300mm-report.png

#7 Stefano

    Member

  • Members(+)
  • 2,173 posts
  • Location: Italy

Posted 13 July 2021 - 00:04

The wavelength you measured is very close to the advertised one. What is the output power, I'm guessing like ~30-60 mW per LED, so maybe around 0.5 W total? What is the claimed value?


#8 colinbm

    Member

  • Members+G
  • 2,741 posts
  • Location: Australia

Posted 13 July 2021 - 00:34

Here are the specs for the LEDs

Product Description:
■ 1 watt High Power LED
■ Colloid Color:Transparent
■ Emission Color: Purple
■ Viewing Angle : 60ºor 120º
■ Forward current: 350-600mA;
■ Forward voltage: 5.7-5.9V
■ Radiant flux(optical power):45-70mW
■ Rohs Compliant

Edited by colinbm, 13 July 2021 - 00:37.


#9 dabateman

    Da Bateman

  • Members+G
  • 3,004 posts
  • Location: Maryland

Posted 13 July 2021 - 04:40

Well if you place a thick sheet of Zwb1 in front of them, you could try UVB induced UVA fluorescence. That is something I have wanted to try.
You would need your Baader venus filter on camera, as it cuts off at 330nmish.

Might be hard to know exactly if you caught the fluorescence though.

Edited by dabateman, 13 July 2021 - 04:44.


#10 colinbm

    Member

  • Members+G
  • 2,741 posts
  • Location: Australia

Posted 13 July 2021 - 05:05

Thanks Dave
I have U325c at 5mm, 255-400nm + IR leak for the LEDs, the IR leak won't happen.
I have a UV cut at 410nm for the camera + a hot mirror. I can't use the Baader U because I won't even see a black cat in a coal mine....but the Baader Hot Mirror will work.

PS the ZWB1 that I have goes past 400nm.

PPS I can use the quartz lens I made recently for reflected light photography to try & see what I get.

Edited by colinbm, 13 July 2021 - 05:10.


#11 JMC

    Member

  • Members+G
  • 1,365 posts
  • Location: London, UK

Posted 13 July 2021 - 07:55

Interesting, thanks for sharing Colin. Really like your LED experiments.
Jonathan M. Crowther

http://jmcscientificconsulting.com

#12 colinbm

    Member

  • Members+G
  • 2,741 posts
  • Location: Australia

Posted 13 July 2021 - 08:51

View PostJMC, on 13 July 2021 - 07:55, said:

Interesting, thanks for sharing Colin. Really like your LED experiments.

Thanks Jonathan
I have enjoyed learning how to make them & sharing them here.

#13 dabateman

    Da Bateman

  • Members+G
  • 3,004 posts
  • Location: Maryland

Posted 13 July 2021 - 09:02

Colin,
I meant used these Leds as the light source with a filter to block UVA and Visible. An 8mm thick u340 has peak at 330nm, with about 50% transmission at 309nm, and only 40% at 360nm, dropping hard.
Then use Baader venus u on the camera with a lens that isn't good less than 350nm, like the Canon 40mm STM.
The point is to see if you can get UVA fluorescence from the UVB light source.

Tryptophan has peak absorption at 280nm that tails off into 300nm. The emission is in the UVA at 350nm. Seeing something like that is what I was implying.

Edited by dabateman, 13 July 2021 - 09:05.


#14 colinbm

    Member

  • Members+G
  • 2,741 posts
  • Location: Australia

Posted 13 July 2021 - 09:07

Thanks Dave, the penny has dropped now thanks.
But I can't do 8mm U340 ?