Anyone ever see this before? This is room temp thermal imaging….in SWIR.
Last week I tested out a new lens on my Goldeye G033, an InGaAs camera , and was pushing its sensitivity to the max while thermally imaging some very hot water in a dark room.
As the water cooled, I upped the integration time, retaking dark frames along the way to compensate for the increase dark current.
Eventually it was imaging the water spitting distance from human body temperature so I decided to set the exposure to a value way higher than recommended and plopped myself in front of the camera in a pitch black room.
suddenly, something I’ve long wanted to see but haven’t seen anywhere, proved possible. Thermal images of ambient temperatures in shortwave.
This was a run of the mill spectral range InGaAs SWIR (0.94um-1.68um), not eSWIR or anything fancy, by the way. I’ve tested that with a monochrometer. And for this test I doubled checked that it wasn’t sensing longer wavelengths using an IR AR coated germanium window around 7mm thick. Couldn’t see a thing.
Closest I’ve seen to ambient thermal imaging in Swir used a 1-2.5um MCT cryocooled camera at -196C. That’s a lot longer wavelength than this topped out at. Also my camera was running at -14C.
What can you do at this short of a wavelength with thermal imaging? Well theoretically it’ll provide higher contrast than even MWIR, always, if you can get ample signal to noise. That’s just a consequence of spectrally integrating the Stephan Boltzmann law.
Camera: goldeye G033 TEC1, 640x512 15um pitch, -14C FPA with addition of a water cooling block I added.
Lens: SOLO50 F1.4 50mm from sensors unlimited
Since I definitively proved to myself swir cameras are room temp thermal cameras under the right conditions, I wanted to show that LWIR thermal cameras can “not” be room temp thermal cameras if they image mainly scattered light (in the same post). Something I rarely see as well, but is quite easy to show.
A 120C heating element did just the trick for this, hot enough to illuminate a scene with ample longwave, but not too much to cause surface heating from shorter wavelengths. A nearby fan helps with this since I still had to get real close to it for this to look nice.
The LWIR light overwhelms most of the thermal emission of an object revealing a completely invisible world that looks a lot more like SWIR aught to look at this temperature, rather than LWIR.
At 13000nm, water absorbs 99% of incident light in the first 25um or so, assuming no reflections. That’s roughly 200 times shorter than at even the strongest absorption band in swir (1450nm.) So in reflected LWIR, my entire eyeball’s surface is rendered a solid shade of black from its water content… wild.
LWIR images were captured with an HTI301 LWIR VOx 384x288 pix 17um pitch. “55mk” whatever that means in the context of the true noise specs of a camera. Nothing fancy, so feel free to give it a whirl on a higher resolution sensor and post!