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UltravioletPhotography

Candle Flame with UV Imager


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WiSi-Testpilot

Colinbm, thank you for your nice spectra. Now I have tested it with a new butane lighter. The result is basically the same as with a candle. The candle is a bit brighter. The daylight leak is not a problem for me. For the planned representation of the corona discharges, the leak should add the landscape.

So I'll stop at this point. I've learned a lot.

Best regards,

Wilhelm

 

Butane Lighter, 270 nm, 500 ms, with and without a 5 mm glass plate

post-210-0-85541200-1603562620.jpg

 

 

Candle from #18, 270 nm, 500 ms, with and without a 5 mm glass plate

post-210-0-22465900-1603562642.jpg

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Using the numbers from Colin's low pressure mercury bulb is interesting.

At 800nm we have 0.007mW/cm2. The plot for the GSENSE 2020BSI has the exact same quantum efficiency at 250nm as at 800nm.

So that could divide out.

Thus assume OD3 blocking filter and you have the following:

@800nm, 0.007mW/cm2 x 0.001 x 0.62 = 4.34x10-6

@250nm (ionizing), 0.085mW/cm2 x 0.3 x 0.62 = 1.58x10-2

 

@250nm, 0.085mW/cm2 x 0.3 x 0.28 = 7.14x10-3.

 

So using the correct light you may not see any IR leak in your UVC images using your current filter.

 

I am just assuming its OD3 Blocking, it might be better, as your candle IR leak wasn't super bright, and it would be summed over more IR wavelengths.

 

I am ignoring the lens transmission as it doesn't matter much. Basically 84% in the IR and 88% at 250nm. I know it cuts off hard at 220nm though. So not the best lens for deep UV-c.

Here is a link to some of its spectrum, starting at 250nm into SWIR:

https://www.universeoptics.com/wp-content/uploads/uv2528b_trans_curve.pdf

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WiSi-Testpilot

Thank you for your calculations. I am very happy with the setup, but as you wrote, the candlelight is not optimal to test the UVC sensitivity.

Best regards,

Wilhelm

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Yeah, colin's spectrum says it all, really. The flame is weighted very strongly toward IR so needs fantastic blocking in that region if you truly want to see the UVC only. Wilhelm, your setup is fine if you just use a light source that is mainly UVC and not mainly IR with a tiny bit of UVC.
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Thank you for your calculations. I am very happy with the setup, but as you wrote, the candlelight is not optimal to test the UVC sensitivity.

Best regards,

Wilhelm

 

Actually for testing I think you nailed the worst case scenario. You still see UVC on the bottom and sides. Its not totally blown out by the IR leak at the top. So this is a good way to stress test for leaks.

If I get a UVC capable sensor, this will be my first test.

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