Low cost camera for viewing CO2 absorption

[zcgdave]

Hello all!

I'm an Electronic Engineer, but I have a side-hustle in communicating Climate Change. I've had this idea to setup an exhibit where you view a light source (visible + IR, like a candle or incandescent bulb) through air, and then through a container of CO2. Well, its kinda a rip-off of this:

).

The idea being, in both cases the light will be visible to the eye, but if viewed in IR, the light source won't be visible though CO2 due to it's absorption of IR, thus, demonstrating the Greenhouse effect (kinda).

CO2 absorbs well at about 4.25 microns (https://webbook.nist.gov/cgi/cbook.cgi?ID=C124389&Type=IR-SPEC&Index=1) and you can buy a fairly inexpensive bandpass filter that aligns with the absorption region (https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=5871). BUT, what I need is an MWIR camera that sees 4.25 microns, but that doesn't cost an arm and a leg!

I have basically no requirements for resolution and frame rate. 1fps would be completely fine, and only a hand full of pixels would be OK.

Does anyone have any ideas about the sort of camera that would do the job? Obviously I can see that MWIR cameras exist, but the ones I can find look VERY high end and prohibitively expensive for my science experiment.

Any thoughts or recommendations would be appreciated!

[Vipitis]

Option 1 is finding an ebay bargain (which some of the forum members managed for mwir cameras)

Option 2 is using a single pixel diode and scanning x,y (which has been done once on this forum)

Option 3 is securing funding to buy a optical gas imaging camera

[unturned3]

Option 2 is using a single pixel diode and scanning x,y (which has been done once on this forum)

Hmm... interesting. Is there a link to this thread/post? I have no idea what keywords to enter in the forum search bar.

[Vipitis]

Found it here: https://www.eevblog.com/forum/thermal-imaging/diy-pinhole-thermal-camera/

If you manage to find a photodiode in the correct wavelength you can attempt optical gas imaging in, but it will take more than a second per frame, so anything moving will be really tricky.

[zrq]

In principle, any microbolometer based thermal camera are inherently wideband and should work for you if the optics is transparent at 4.25um (which I believe is usually the case). If you want a cheap device and can work with very few pixels, there are products like MLX90640 or HTPA.

[mikeselectricstuff]

A pir sensor with a chopper may be another option for a single pixel sensor

[ArsenioDev]

A pir sensor with a chopper may be another option for a single pixel sensor

If you're specifically looking to sense CO2 via transmissive attenuation, I worked on an instrument based around a chopper and a lock in amplifier that flew offworld in 2019.

Here's a link to the paper (https://link.springer.com/article/10.1007/s00340-019-7315-8) used an InGaAs detector but you can totally switch to a narrowband filtered detector that's a fair bit nicer from Hamamatsu to get even better single gas performance.