365nm UV Flash?

[Andrea B.]

I would have to go to the gym daily to deal with that giant Bjørnian Broncolor. For field work you would need a sherpa and a llama to carry the battery pack and light and accessories. I managed a couple of shots with it while in Norway, and it is for sure an excellent UV lighting tool in the studio.

 

I've gathered a few flowers and written myself a note to experiment with UV flash induced Visible fluorescence this evening when it grows dark.

[baffe]

Andrea like you I don't like that heavy battery packs!

 

http://up.picr.de/22627115hb.jpg

[Andrea B.]

:D

[nfoto]

That contraption should be able to power at least one studio flash :D

 

(my field battery weighs a more modest 10 kg and comes in form of a portable back pack).

[baffe]

Puuhh 10kg is not my favourite backpack. Of course easier to move than a generator.

 

But I needn't take care of a kilowatt of load more or less.

[JCDowdy]

Pylon,

 

Reading back through this post, I seem to have failed to respond to several of your questions. Not intentional, my work has me traveling lately and madly trying to catch up when home.

 

Let me reiterate I am only experimenting with this myself and have nothing definitive to show. I have not tried a stack on the flash, only the KOPP 9863 that I shared with Johan. He posted results better than mine. I have used a filter stack (1mm U-360 & 1.5mm S8612) to clean up UVIVF on an ~375nm LED. When I figure out a good way to attach 52mm filters to my flash I will surely give it a try.

 

I the meantime here are a couple of credible sources, to assure you the approach is not simply conjecture. Some I seem to recall have been discussed previously on UVP.

 

Verri, Giovanni, and David Saunders. "Xenon flash for reflectance and luminescence (multispectral) imaging in cultural heritage applications." British Museum Technical Research Bulletin 8 (2014): 83-92.

 

Dyer, Joanne, Giovanni Verri, and John Cupitt. "Multispectral Imaging in Reflectance and Photo-induced Luminescence modes: A User Manual." British Museum, CHARISMA Project (2013).

 

see also:

CHARISMA Project Technical imaging

[Johan]

John, excellent papers, thank you for that. I note with wry satisfaction that the bodge way I attach my filters is almost exactly the same as the photo illustrated in the first of the papers. If you want to send me the dimensions for your flash head at their end (ie what size sleeve would fit over your flash) via a PM I'd be utterly delighted to make one for you and send it over.

[Johan]

Polarizer foils are both, very sensitive to overheating and expensive.

 

Yes - I've used polarizing foils before for cross polarisation and they heat up and get destroyed quickly. If you can put some uv transmitting perspex between the flash and the foil that'd help absorb heat before it reaches the foil/gel. Transparent CD covers transmit UV, that worked for me

[JCDowdy]

John, excellent papers, thank you for that. I note with wry satisfaction that the bodge way I attach my filters is almost exactly the same as the photo illustrated in the first of the papers. If you want to send me the dimensions for your flash head at their end (ie what size sleeve would fit over your flash) via a PM I'd be utterly delighted to make one for you and send it over.

 

You are welcome and appreciated!

[baffe]

In

 

https://www.academia.edu/9469495/Xenon_flash_for_reflectance_and_luminescence_multispectral_imaging_in_cultural_heritage_applications

 

i find a Diagram that makes me wonder:

 

http://up.picr.de/22690678tq.jpg

 

Hm in first sight that is the flashtube I was always dreaming of!

 

Under the headline "Xenon flashtube output" is written:

 

"The relative irradiance was calibrated using the blackbody emission of an LS-1 Ocean Optics tungsten halogen light source with a colour temperature of 3100 K."

 

Why do they calibrate a xenon tube vs halogen light source?

[Johan]

That diagram - it tallies with my converted vivitar 285 clone, the cactus KF36, (which is also xenon). But I am finding that there's a tremendous amount of visible violet 390-410ish(?) produced which drowns out the relatively little down in 350NM, regardless of whether I filter it with Baader-U, KOPP 9863 or the custom uv pass filter from my friend at Mineralogical Research Company USA

[Johan]

Under the headline "Xenon flashtube output" is written:

 

"The relative irradiance was calibrated using the blackbody emission of an LS-1 Ocean Optics tungsten halogen light source with a colour temperature of 3100 K."

 

Why do they calibrate a xenon tube vs halogen light source?

 

It seems that when you measure relative irradiance you basically use a 'known profile' to get your values right. See this pdf.

[JCDowdy]

Why do they calibrate a xenon tube vs halogen light source?

 

Because they are very stable and reproducible for use as traceable spectral irradiance standards.

 

Please understand that the spectra shown in Fig 3 are significantly erroneous. This is a major flaw of this paper. The USB spectrometer used simply cannot measure into the UV and while they recognize "...considerable noise in the UV region..." the authors unfortunately do not understand the limitations of such simple spectrometers. For further explanation see: A Comparison of CCD and Scanning Systems for Spectroradiometry.

 

When trying to accurately measure the spectrum of a flash lamp one is faced with the dilemma of measurement speed. A scanning monochromator cannot capture a single flash. There are advanced techniques for correcting errors due to internal stray radiation inside a single fixed grating instrument. Several of these methods must be implemented to collect reasonably acceptable spectra of single high intensity flashes but it seems none were implemented in this paper.

 

It is interesting that the authors clearly understand the concept of ambient stray radiation in the environment so we must assume they were simply misinformed of the even more significant impact of stray radiation inside their spectrometer. I do not fault the authors for that since the sellers of such instruments often make performance claims that stretch the limits of credibility.

 

The reason I linked this paper is primarily for filter stacking combinations given in Table 1. I would advise that the entire section entitled "Xenon flashtube output" simply be disregarded.

[Johan]

That's really interesting, thanks for the explanation.

[baffe]

John of course a CCD-spectrometer is not a precision instrument.

 

But it is good o get an overview. And it is good to check flashes and flashtubes on my workbech while working on flash units.

 

I performed:

 

Dark calibration, calibration on light source (the one I used for the test) and then a transmission measurement. Took care not to override the ccd to avoid straylight. Both twice, first with tungsten halogen second with a flash (Multiblitz Mini Studio with modifications). The filter was a dichroitic daylightfilter that I found on my workbench. Here the results:

 

Filtercheck with Halogen:

http://up.picr.de/22693298ez.jpg

 

Filtercheck with studio flash:

http://up.picr.de/22693301fq.jpg

 

Together:

http://up.picr.de/22693302om.jpg

 

I think the errors between measuring with constant illumination and flash are not that big. Of course much bigger then errors you are used from scanning intruments, but i can check my flashes.

 

And the flash (relative):

http://up.picr.de/22693303nf.jpg

 

And that is what I expect from a relative metering of a flashtube. Of course with tolerances, some more uv, some more vis dependent on several parameters

[JCDowdy]

Sorry I know I asked before, I forget which CCD Spectrometer are you using? I don't recognize it from the screen shots.

 

I suggest when we post spectral measurements we should ID the instrumentation and briefly what type of instrument it is for readers who do not know one model from another.

 

I would like to see a solar spectrum plotted with a log-scale y-axis from your system.

[baffe]

Sorry John. It is a Boehringer Ingelheim MSP12, 12 Channel CCD Spectrometer (9 equipped). Connected to a PC via USB or Serial.

 

Sorry again, but I have no way to Excel or another spreadsheet software from this instrument. I just mail the screenshots from the workshop to the office. I use it only in the workshop for quick checks while working on flash units.

 

You can find a daylight spectrum here, I hope this helps you John:

 

http://www.ultravioletphotography.com/content/index.php/topic/1101-incandescent-lamps-as-uv-source-an-attempt/page__st__20

[JCDowdy]

Thanks Stefan,

I recall looking for specs on your spectrometer once before to no avail.

All I can find is that Boehringer Ingelheim microParts GmbH partnered with a US company called Digilab several years ago and they may be embedding the Boehringer Ingelheim LIGA spectrometer tech into other instruments like plate readers.

 

This is the best I could find: Microspectrometers for Diagnostics,Analytics and On-Line Process Control

 

The LIGA multichannel spectrometer is patented and I think initially developed for separating out multiplexed optical telecommunication bands. It looks like this design handles stray radiation better than the simpler OO USB series. I am intrigued by what you have there. If you can, please send me a link where I might find more information about your particular MSP12 model.

[baffe]

Ok, I try to get some info.

 

But the instrument I have is not designed for measuring on telecommunication bands. Common telecommunication on fibers runs between about 800nm (multimode) to the 1300nm and 1500nm windows (both singlemode). My msp12 runs only to 920nm and dynamics and accuracy is not suffcient at all to measure telecom signals.

 

Especially the complexer DWDW multiplex systems that need use of a spectrometer need very high resolution and level accuracy far beyond those of the MSP12.

[baffe]

Yes, John you are right the instrument is LIGA based.

 

Data from manual file:

 

http://up.picr.de/22696295ag.jpg

[JCDowdy]

Stefan,

I have led you off topic on Evan's interesting UV Flash thread.

I am still trying to find out more about your spectrometer but perhaps we should continue this conversation via PM or in a different thread.

Assuming of course you are willing to indulge me.

[baffe]

John, I do not think that it is so "off topic".

 

If you can check the effect of a conversion, then that's often disappointing and sometimes depressing.

 

Please sent me a PM with a mail address then I will sent the manual of my instrument as a pdf as a first step.

[JCDowdy]

Thanks for the additional documentation.

 

For anyone else interested, Boehringer Ingelheim microParts GmbH formed a spin-off company called INSION GmbH (Heilbronn, Germany).

INSION lists spectrometers but not a 12-channel model.

[colinbm]

Looks like a nice spectroscope Stefan. Does it intergrate with Windows OK. What sort of price are these please ?

Col

[baffe]

As far as I know the 12 channel version is discontinued.

 

The system works well with Windows XP. And after some tricks also on W7.

 

The single channel "evaluation system in metal housing" is about 2000 Euros.