dabateman Posted October 23, 2020 Share Posted October 23, 2020 Below are my series taken using the KSS UV Imager with 60mm lens at F4 with Olympus 30mm Macro at F4 on a Panasonic GM5 positioned on the back imager. No filter: First image 254.3bp25 UVC image: 303bp10 with U340 2mm to block all IR: 313bp25 with U330WB80improved to block all IR: 313bp25 only (Some IR leak even with this): 335bp10 with U330WB80improved to block all IR: 370bp15 with U330WB80improved to block all iR: 395bp25 fitler: Lp 720nm filter only: Last image 254.3bp25 UVC image (incase I could see hot spot in wick): Link to comment
Stefano Posted October 23, 2020 Share Posted October 23, 2020 Two things:It seems the candle is inside a casing. Can its material influence UV images, especially at shorter wavelengths? Your UVC images are similar to those taken by Wilhelm, but not "equal". In particular, the tip of the flame is not bright. Link to comment
dabateman Posted October 23, 2020 Author Share Posted October 23, 2020 No the imager looks above the glass dish, so no influence or glass restrictions. Sadly my images are not the same as Wilhelm's. I now thik his are IR leakage at 254nm. Mine are the same as here with UVC on the edges of the flame:http://photographyoftheinvisibleworld.blogspot.com/2016/12/deep-uv-ultraviolet-reflected-light.html?m=1 I wonder now if the 2020BSI is too IR sensitive and not enough UVC sensitive. Jonathan showed that BSI sensors were 2x to 3x more IR sensitive than FSI sensors. So I don't know if its the sensor being more sensitive to IR than UV and really bad IR leak on his 250bp filters or if the sensor isn't strong in UVC sensitivity. Also he had dark water at 313nm. Thats not right. That is clearly IR high band leakage. Link to comment
Andy Perrin Posted October 23, 2020 Share Posted October 23, 2020 Yeah, I was beginning to suspect as much when his results didn't match Klaus's. Link to comment
Stefano Posted October 23, 2020 Share Posted October 23, 2020 Wilhelm, if you are reading this, try to put an IR longpass filter (such as Hoya R72) on the lens, with your UV filters, and see if you can see something and in case you can, how much leakage you have. As Steve (Cadmium) says, if you see something with the same settings, you have a leak. Link to comment
WiSi-Testpilot Posted October 23, 2020 Share Posted October 23, 2020 David, please take the 250 nm image again, but in front of the sky. At 254/25 nm the sky is dark. Maybe there is some leak. I have documented the full spectrum leak and think it’s ok.Stefano, I will try it tomorrow.Best regards,Wilhelm Leak test at high gain. Link to comment
Andy Perrin Posted October 23, 2020 Share Posted October 23, 2020 WiSi-Testpilot, the thing is that the ratio of IR to UV of the candle matters a great deal here. If there is only a little UV and a lot of IR (as one might expect), the IR could dominate, regardless of what the tree/sky/roof look like. The IR from the lighter might be much stronger than all of the above, and the UVC negligible in the relative sense. Link to comment
WiSi-Testpilot Posted October 23, 2020 Share Posted October 23, 2020 Andy, ok, I understand. Nevertheless I would like to see a flame infront of the sky.Best regards,Wilhelm Link to comment
dabateman Posted October 23, 2020 Author Share Posted October 23, 2020 I will see if I can squeeze that in tomorrow. Are you using a butane lighter? I think I only have matches and candles. I may have some butane that I could light though. Will have to look through my chemicals. Link to comment
dabateman Posted October 23, 2020 Author Share Posted October 23, 2020 Andy or Stefano,How do we calculate the area signal?Lets assume the quantum efficiency x fill factor plot to be correct for the 2020BSI sensor. Now lets assume OD3 blocking in IR for Wilhelm's filters, as thats common and 30% sinal as indicated in his plots.How much IR is comming through over the sum of 700nm to 1100nm vs area under the 250nm peak?I wonder if its very close As in 400 x IR leak x QE vs 25 x 30%peak x QE. Link to comment
WiSi-Testpilot Posted October 23, 2020 Share Posted October 23, 2020 I will see if I can squeeze that in tomorrow. Are you using a butane lighter? I think I only have matches and candles. I may have some butane that I could light though. Will have to look through my chemicals.Thank you, I'm very excited. I think it doesn't matter if you take a candle or a lighter.How long is your exposure time at 250 nm? Link to comment
dabateman Posted October 23, 2020 Author Share Posted October 23, 2020 My exposure for the candle was 1/2.5 at ISO 200. My exposure for the LP 720 filter was 1/30 at ISO200. The sensitive is significant less at IR than UV for the imager.I would assume about 6 stops more IR than UVC in the candle. Link to comment
Andy Perrin Posted October 24, 2020 Share Posted October 24, 2020 Andy or Stefano,How do we calculate the area signal?Lets assume the quantum efficiency x fill factor plot to be correct for the 2020BSI sensor. Now lets assume OD3 blocking in IR for Wilhelm's filters, as thats common and 30% sinal as indicated in his plots.How much IR is comming through over the sum of 700nm to 1100nm vs area under the 250nm peak?I wonder if its very close As in 400 x IR leak x QE vs 25 x 30%peak x QE.I don't think that kind of calculation can be done without knowing the emission spectrum of the flame. Like, you would have to integrate (flame emission)x(lens transmission)x(filter transmission)x(fill factor)x(QE) I think, for each range? Link to comment
Stefano Posted October 24, 2020 Share Posted October 24, 2020 We don't know the exact spectrum of the flame, but Wilhelm linked one in his topic: https://www.dguv.de/medien/ifa/de/fac/strahl/pdf/uv_expositionen_gasbrenner.pdf The lens shouldn't matter much, as it should have a flat transmission curve. Anyway it is quite a complex calculation, you have to do it for every point (like every nanometer) and then summing all points together to get the area under the curve. Link to comment
colinbm Posted October 24, 2020 Share Posted October 24, 2020 Shouldn't the flame spectrum represent the atoms being consumed ? Link to comment
colinbm Posted October 24, 2020 Share Posted October 24, 2020 I have taken a spectrum of a household domestic candle flame..... Link to comment
colinbm Posted October 24, 2020 Share Posted October 24, 2020 Household domestic candle flame with S8612 on spectrometer... Link to comment
WiSi-Testpilot Posted October 24, 2020 Share Posted October 24, 2020 Colinbm, thank you, that is very interesting.I made images with and without a 5 mm glass plate between the camera and the candle. Before opening the other thread I had tested it with the lighter, but not with the candle.Later I will repeat it also with the lighter and with an IR Filter. I need an additional short pass filter. Which one can you recommend?Best regards,Wilhelm 270 nm, 500 ms, with and without a 5 mm glass plate Link to comment
dabateman Posted October 24, 2020 Author Share Posted October 24, 2020 That's the problem. There isn't a good short pass filter.At 300nm and 313nm you can use U340 on its own. That helps cut out a lot of IR, but can't use U340 below 300nm. U330 allows the lower UV. But also the higher IR. Excellent IR blocking filters are hard to get. I gone back and forth with a lot. Link to comment
colinbm Posted October 24, 2020 Share Posted October 24, 2020 Short pass filter is a dodoIt has been on my wish list a long time.... Link to comment
dabateman Posted October 24, 2020 Author Share Posted October 24, 2020 Thanks Colin I think you gave us the answer. That a candle flame is the best UV filter stress test. You should be able to see the IR leakage through the BaaderU filter with this test. So if we assume incomplete ionizing radiation at 250nm for the 2020BSI sensor, then a pixel will have 28% qe. Assumeing 100% ionizing radiation and its 62%.At 850nm the qe is 50%. So for 850nm candle with an OD3 blocking filter is 0.001x0.5x0.005 mW/cm2 = 2.5x10-6.At full ionizing radiation 0.3x0.62x0.00001 = 1.86 x10-6 So there is twice as much detected 850nm light going through the filter than 250nm light. So lets not use candles as UV light sources.Best to see if you can get your hands on a 254nm low pressure mercury bulb. The cost has come down. Also ypu can buy a portable one cheap, that are typically used for short wave rock hunting. Link to comment
Stefano Posted October 24, 2020 Share Posted October 24, 2020 Shouldn't the flame spectrum represent the atoms being consumed ?Maybe I understood what you meant. If you exite atoms on a flame they will emit light according to the energy level gaps between different electron energy states. I tried a famous experiment: take some cotton or a piece of paper towel, soak it into salt water and put it on a flame. If you look at the spectrum of the flame (I tried with an "eye spectrometer" I made with a slit and a diffraction grating) you will see the 589 nm sodium yellow line. They are actually two very close lines, at 588.995 and 589.5924 nm. The difference is basically spin up/spin down. Maybe with a very narrow slit and a good eye you can see the doublet. Link to comment
colinbm Posted October 24, 2020 Share Posted October 24, 2020 I have this UVC + UVvacuum lamp, but it produces ozone, but when I wrapped the tube with 5 thousands/inch clear Mylar it was eliminated, but please treat this carefully & do your own tests to be satisfied you are free of ozone & protected from the UVC radiation. https://www.ebay.com.au/itm/8W-Ultraviolet-Germicidal-Tube-Lights-Ozone-Home-Travel-Disinfection-Lamp/373046702522?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 Uncovered bare tube.... Covered tube with Clear Mylar..... Link to comment
colinbm Posted October 24, 2020 Share Posted October 24, 2020 Maybe I understood what you meant. If you exite atoms on a flame they will emit light according to the energy level gaps between different electron energy states. I tried a famous experiment: take some cotton or a piece of paper towel, soak it into salt water and put it on a flame. If you look at the spectrum of the flame (I tried with an "eye spectrometer" I made with a slit and a diffraction grating) you will see the 589 nm sodium yellow line. They are actually two very close lines, at 588.995 and 589.5924 nm. The difference is basically spin up/spin down. Maybe with a very narrow slit and a good eye you can see the doublet. Yes I was mistaken, you are correct. Link to comment
colinbm Posted October 24, 2020 Share Posted October 24, 2020 The Butane Lighter flame spectrum is slightly different.... Bare flame... Flame with S8612... PS, unfortunately the data gets truncated at the ends as it is too small, so on the UV end it will continue along further at the lower end, tapering away.... Link to comment
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