is thermal illumination possible on the cheap? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: November 03, 2020, 09:05:38 am
content: For a thermal camera I have noticed that you can use a soldering iron to illuminate something you are looking at. Naturally a heat lamp seems like the next step up with reflectors. To look at a surface as a IR reflector, not for temperature measurement.But, is there a way to further step it up? In terms ofcheapfilters used to bandpass filter something like a heat lamp?Just for fun, say to get the wavelength output into a few ranges.Also I assume there is some amount of control offered by voltage control of the heat lamp to adjust temperature.Has anyone done anything interesting with this looking at cold samples for whatever reason?I thought maybe a space heater would do a good job, if you string out some coils infront of some kind of reflector (parabola?), then connect it to a variable power dc switching supply on a battery.. it is possible to do a decent one because I have a milwakee 18v battery heat gun that is pretty decent at heat shrink and stuff (but its weak compared to a wall model, which is usually overkill unless you are doing paint stripping or whatever).I know for visible optics you can get some kind of adjustable grating or prism that gives you a narrow wavelength output, but they seem small and low power, despite the nanometer adjustability. A thermal one would be good for a microscope, but I don't know the details. Do you need exorbitantly priced parts? Or can you make something on a milling machine (the grating) because the wavelengths are long? (the first difraction grating for optics I think was made one some kind of tricked out milling machine, much like the first gauge block made on a tricked out sowing machine).

author: Fraser
author_rank: Super Contributor
timestamp: November 03, 2020, 10:44:05 am
content: Active thermography is normally broad spectrum illumination and not narrow band. Halogen lamps or powerful flash guns are Commonly used. Any filtering would normally be done at the camera and not the illumination source. A filter at the illumination source would need to cope with very high levels of energy, whereas the levels reaching the camera lens are far more manageable.IR filters outside the common NIR types used in photography are expensive as they are of complex design using special coatings. Not really a DIY proposition.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: November 03, 2020, 01:28:04 pm
content: If you are looking to carry out FTIR Spectroscopy, a LWIR camera is not the correct tool for the job.Fraser

author: coppercone2
author_rank: Super Contributor
timestamp: November 03, 2020, 04:04:42 pm
content: I actually have a proper LN cooled detector for that application (save for the optics and crystal), but I am actually interested in the topic as in bulk on the fly views of themrography, I do not want to work on the slide rails and actuators and other stuff involved in the spectrometer (not interested in ANOTHER VNA type thing!). Its a rack mount that does precisely nothing useful to me that cost way too much to see invisible things in boxes you can never open. electrons are playing tony hawk in those filters causing a 300$ a month power bill!(my previous experience when I started fooling around with the microwaves). Not saying its not interesting but if you mess with those too much its traumatic.I thought it would be cool to walk around with a battery powered heat lamp to see at IR reflections of different things. Trying to have fun with the portability of the seek thermal (consider it a artistic application)

author: bap2703
author_rank: Regular Contributor
timestamp: November 05, 2020, 12:17:33 pm
content: Thin black LDPE film (aka trash bag) might do the job as a visible-block/lwir-pass cheap filter.Ftir spectroscopy works with a lwir camera, although you'll often want a faster and more sensitive sensor with also a broader spectral range.Sources in FTIRs for LWIR bands are silicon carbide ribbons, the electricity bill can be high because you might want to leave it turned on for maximum stability of the output light.Basically what you want for LWIR illumination is a lamp without that pesky IR blocking glass bulb.If stability of the flux is not an issue it's perfectly doable to turn it on and off as needed.It might also be clever to do differential imaging: image viewed = image with light ON - image with light OFFThat way you don't need to have a light source that is super bright in order to overcome the "light OFF" infrared flux coming from your scene.

author: coppercone2
author_rank: Super Contributor
timestamp: November 05, 2020, 03:50:16 pm
content: could you short circuit heat graphite rods infront of a parabolic reflector? I know SiC has a better thermal conductivity.. is that why its used?20x thermal conductivityI see SiC on ebay for cheap, but I have some graphite rods (this whole thing seems dumb and I don't want to buy stuff on ebay unless it makes a big difference)

author: bap2703
author_rank: Regular Contributor
timestamp: November 05, 2020, 08:19:09 pm
content: That's more material sciences and I don't know much about that.You'd want less thermal conductivity => that way for a given electrical power your source would be hotter.But the main criteria would be resistance to oxidation.

author: bap2703
author_rank: Regular Contributor
timestamp: November 06, 2020, 11:48:44 am
content: By the way, some people here might find that interesting: thermal illumination NOT on the cheaphttps://sbir.com/PDFs/SPIE-Std-Products-Publications/Bolomoters_Running_Backward_2006.pdf

author: coppercone2
author_rank: Super Contributor
timestamp: November 06, 2020, 01:06:31 pm
content: unit under test: entire submarine LOLso that is a heat projector

author: Fraser
author_rank: Super Contributor
timestamp: November 06, 2020, 01:36:04 pm
content: Active thermography can be a powerful tool in revealing detail not visible in passive thermography. Such is used to discover delamination in carbon fibre areas of modern aircraft or voids within materials. Active thermography can push energy into a surface that would normally be of equal flat temperature profile and emissivity, and pull additional information out of the scene by observing how the target behaves as it increases or decreases in temperature. This is somewhat different to your desire to image different wavelength reflectivity though. That particular area of imaging is of interest to the military in order to detect camouflaged or hi-tech stealth targets.The active thermal emitter array is also a potential means of concealing a targets heat signature by creating an active emission to mimic a ‘non threat’ silhouette on a battlefield. All very clever stuff. I have yet to read the above referenced document but active emitter technology is an interesting topic so I will study it laterFraser

author: Ultrapurple
author_rank: Super Contributor
timestamp: November 06, 2020, 02:00:22 pm
content: While reviewing the document linked by bap2703 I came across the name Bly (eg Bly Cell) - he hasa host of infrared patents to his name that make very interesting reading.

author: coppercone2
author_rank: Super Contributor
timestamp: November 06, 2020, 02:44:32 pm
content: Quote from: Fraser on November 06, 2020, 01:36:04 pmlol, I just want to look at reflectivity under different wavelenghts. I noticed this when I made a home made soldering microscope with badly adjusted optics, UV light looked blurry, but red light was fine, and I had a BW camera, and I was using optics removed from various things without modifying the threads, so I made a system which barely worked on the edge of the red light range, to my understanding, so my light ring actually was made of red power LEDs. This was from a old CCD camera I found in the trash. I am not sure if thats why, but I also did notice scratched surfaces are reflective to IR without flaw (brush finish steel)I think that sounds silly because you won't project heat far and the military will just make a bigger bomb?I expect this thing to be a clunky bastard apparatus that is not suitable for anything related to something other then a scientist walking around with something akin to a old lantern, or maybe doing clear coat paint jobs.

author: adammunich
author_rank: Contributor
timestamp: November 16, 2020, 08:57:43 am
content: I use these in a reflector lamp holder they work amazingly well, and provide lots of MWIR light too unlike halogen lamps.https://www.processheating.com/products/air-load-bank/cone-heaters/

author: Fraser
author_rank: Super Contributor
timestamp: November 16, 2020, 12:18:53 pm
content: In the 1960’s PIFCO made IR heat lamps that employed a similar open heater element and reflector.Sadly they are quite collectible these days so can be expensive.

author: Bill W
author_rank: Super Contributor
timestamp: November 16, 2020, 04:05:09 pm
content: Quote from: Fraser on November 16, 2020, 12:18:53 pmThere is the gas powered version used by this Bullard rep camera torture comedy videoBill

author: Gyro
author_rank: Super Contributor
timestamp: November 16, 2020, 08:26:44 pm
content: Quote from: Fraser on November 16, 2020, 12:18:53 pmIf you look on Amazon (for example), quartz element and reflector IR heaters are still very much alive and kicking at a wide range of prices. The exposed element ones are long gone, but not the quartz tube enclosed ones.

author: Fraser
author_rank: Super Contributor
timestamp: November 16, 2020, 09:33:24 pm
content: Gyro,I think the advantage of the “open element” type is its output spectrum is not dictated by the passband of the Quartz Glass envelope used on modern enclosed heater elements.Fraser

author: Gyro
author_rank: Super Contributor
timestamp: November 16, 2020, 10:08:23 pm
content: Good point. I'm not sure if the quartz tube being at roughly the same temperature as the element mitigates this to some extent.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 16, 2020, 11:37:26 pm
content: All of the potential sources mentioned are thermal sources (roughly black body emitters). The cameras are typically sensitive in the 7-14 micron range, so for anything much above room temperature the peak emissions will be out of the cameras range on the short end. Most of the power will be wasted. Quartz envelopes and the like are probably a benefit since they increase emitting area and presumably emissivity since transmission and emissivity tend to be arithmetic inverses. The other thing that comes out of this is that unlike visible light sources there is really no huge benefit of operating the heating element at thousands of degrees. Think of your soldering iron which provided good illumination from a small area and modest temperature. No need to fret about burning or melting your emitting element, it just doesn't need to get that hot. Something like a propane torch with a disk of black iron a ten to twenty centimeters in diameter mounted in the flame might turn out as a good source a relatively portable. If being tied to a long extension cord is acceptable a stove top heating element makes a pretty decent source.More exotic emitters that put all of their output in the desired band would be interesting, but not too practical. Something like the CO2 laser out of one those laser engravers. Many fun details such as safely spreading the beam, packaging it so that it is "portable", and dragging around the power cord.

author: coppercone2
author_rank: Super Contributor
timestamp: November 17, 2020, 02:17:06 pm
content: I think mr.heater propane catalytic fits the bill, I need to try it, then see if I can miniaturize it. The problem is they are sensitive to motion. And it makes ALOT of hot air. But another idea anyway

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 17, 2020, 02:42:16 pm
content: Quote from: coppercone2 on November 17, 2020, 02:17:06 pmThat should work. Making an adaptor to use a small bottle shouldn't be too hard. The 25# bottle they are usually on would be a tad awkward.

author: coppercone2
author_rank: Super Contributor
timestamp: November 17, 2020, 10:27:08 pm
content: Mine uses two propane tank cylinders (blow torch), so it is SOMEWHAT portable, but its not what I imagined with 'scanning around" something holding it with 1 hand. Maybe arnold. Too heavy even on one tank. I wanted something like the milwakee m12 bar flashlight (like the ones you use when working on a car).https://campingwithgus.com/2018/01/01/winter-camping-catalytic-tent-heater-review/I will try the mr heater first.Anyone can think of interesting targets to look at?https://campingwithgus.com/wp-content/uploads/2018/01/catalyticheatermrheater127x216.jpg