Different Spectral Responses from Different Uncooled Thermal Cameras - Page 1
Forum section: electronics / general

author: LMasterGame
author_rank: Contributor
timestamp: September 01, 2025, 07:16:57 pm
content: Yesterday, my new toy arrived, it was the Dali D8X3N thermal camera, and I wanted to do some comparisons with my previous thermal cameras to appreciate the higher resolution.When I was comparing the cameras, I realized that one of them had a response completely different from the others when looking at an old filament bulb.The 4th attachment are the 3 thermal cameras I own:- The left one is a generic Hikvision 256x192 VOx camera. I got it because it has better FOV than other cameras I own.- The center one is the Dali camera, it has an a-Si sensor, with a resolution of 640x480. Its sold at great price in the second hand market considering its resolution.- The right one is a Magnity MAG160-Core, it is a 160x120 VOx camera. Its my first thermal camera.The 1st attachment is the filament bulb captured with the Dali camera.The 2nd attachment is the filament captured with the Magnity camera. Its the same as the previous image, but with the 16th fraction of its resolution.The 3rd attachment is the filament bulb captured with the generic Hikvision camera.Note how only the generic Hikvision camera can see directly the filament, while the others can only see the heat of the glass (makes sense, since glass is opaque in LWIR light) and the closer the glass is from the filament, the hotter it gets.This makes me believe that this camera can see high temperature MWIR sources, or at least, it has different lens material or coating that let it see a non typical LWIR spectral window.What do you think?

author: gamerpaddy
author_rank: Regular Contributor
timestamp: September 01, 2025, 07:47:25 pm
content: interessting.that would mean the hik can see around 4..5µm? maybe the window above the sensor makes all the difference.i also noticed that some thermal cameras are more or less affected by 10.6µm from a co2 laser.when i tried filming one with my seek reveal a few years ago, it almost burned the sensor from a indirect diffuse reflection. it left a streak that slowly ffc'd away over minutes. it was at a very low power.but with a flir lepton, i could film it all day. even at higher power.same with a tiny1c in p2 and my phone.

author: unturned3
author_rank: Contributor
timestamp: September 01, 2025, 08:42:32 pm
content: Quote from: gamerpaddy on September 01, 2025, 07:47:25 pmAs in, these cameras don't see anything when the laser is on? Or do they see a faint spot or something?I thought CO2 lasers absolutely destroy thermal cameras if they see near the 10um band. A previous post on this forum mentioned something similar (although I cannot find it).

author: gamerpaddy
author_rank: Regular Contributor
timestamp: September 01, 2025, 08:51:04 pm
content: they saw the spot thats getting hot from the laser but it wasnt overwhelming.the seek seems to have seen the laser itself, bright as if you point into the sun.

author: LMasterGame
author_rank: Contributor
timestamp: September 01, 2025, 08:51:40 pm
content: Quote from: gamerpaddy on September 01, 2025, 07:47:25 pmThanks for the graph, I wasn't 100% sure if it was MWIR light, but now I am.Thank god your seek camera survived, I remember seeing that happened in an old post from this forum.Also let me take the opportunity to thank you for the documentation on the Dali camera, although I'm not going to hack my camera any time soon, I will eventually, and your documentation and code are great references

author: Vipitis
author_rank: Frequent Contributor
timestamp: September 01, 2025, 11:07:50 pm
content: I wonder how much the window, lens and coatings impact here. Also any kind of histogram equalization/AGC.Is there a Ge prism or diffraction grating to do like spectroscopy? I would love to compare a few of my cameras and lenses but calibration might be difficult.

author: Fraser
author_rank: Super Contributor
timestamp: September 02, 2025, 01:28:42 am
content: The ability of microbolometers to image MWIR targets, especially high temperature targets, was discussed by ULIS back in 2005. The ability of a microbolometer to image energy in the MWIR 3-5um band is dictated by the properties of the microbolometer window and associated lens system. In many systems it is advantageous to limit the spectrum coverage to the standard LWIR band and sensitivity in the MWIR band could be considered a failing in the window filtering performance. It should be noted that the lower sensitivity of a microbolometer at MWIR wavelengths means that it is best suited to image high energy targets, in this case, a tungsten filament.The SPIE article by ULIS may be found here…..https://www.spiedigitallibrary.org/conference-proceedings-of-spie/5783/0000/MWIR-uncooled-microbolometer--a-way-to-increase-the-number/10.1117/12.605335.shortThere has been some work over the years to create a more affordable MWIR thermal camera that does not require the expensive cooling system normally required. Sadly the physics of the situation dictate that the thermal sensitivity remains very low compared to a cooled MWIR camera.Fraser

author: LMasterGame
author_rank: Contributor
timestamp: September 02, 2025, 01:47:14 am
content: I can definitely see why the sensitivity to MWIR is a "defect". However, as a non-professional hobbyist, I take that as a plus instead, even if its low sensitivity

author: Fraser
author_rank: Super Contributor
timestamp: September 02, 2025, 11:13:07 am
content: In your image it appears that you have adjusted the level and span to best image the filament and ignore the cooler thin glass envelope. Did you attempt the same level and span adjustment on the other two cameras ?Fraser

author: LMasterGame
author_rank: Contributor
timestamp: September 02, 2025, 11:48:54 am
content: I only applied a minmax function on the raw 16bit images and mapped those values to 8 bit per pixel, the filament just happens to be extremely bright compared to the scene.

author: Fraser
author_rank: Super Contributor
timestamp: September 02, 2025, 01:46:48 pm
content: That is interesting to hear. Thank you for clarifying the camera setupI will have to test some of my cameras and cores against a similar lamp to see if any exhibit the same capability.Thank you for sharing this interesting discoveryFraser

author: LMasterGame
author_rank: Contributor
timestamp: September 02, 2025, 01:51:54 pm
content: One small clarification that is worth noting, is that the bulb is completely clear (there are no paint layers).Also, the bulb is just 7 watts, so no absurd amounts of power are required.