Playing with LWIR Thermal imaging - Moose et al.

[otoien]

I discovered that we had available a Seek Thermal Compact image accessory for Android phones at work and got to play with it over the holydays. This is the consumer model with the lower resolution, still with higher resolution than competing FlirOne Pro models, but without visible light overlay.  Among targets I tried was a group of moose I encountered down the road where I live  behind a snow berm - I kept a safe distance as conditions are difficult for them now and I did not want to stress them out. Can you detect how many moose there are in this image?

#1

 

 

Stretching neck to feed
#2

(The calibration of the device is way off when taken outside, it was about -10°C)

 

 

At the start they were hiding behind a snow berm
#3

 

 

Another test, my hand in a  comfortable environment.
#4

 

And after coming in from a short trip outside (I live in a dry cabin):
#5

 

Heating tea water - note that the shiny metal in the body and lid does not radiate much at these wavelengths, only the transparent view port and plastic parts close to the body.
#6

 

The tea is brewing. The hot part behind the tea pot is not warm, but a reflection of the tea pot in a shiny steel kettle.
#7

 

The heater in my cabin is idling, but still warm and has warmed up things around it.
#8

 

A food for thought is how far technology has developed. The very first thermal imaging camera I used when teaching physiology 30-35 years ago was bigger than many beefy telescopes , was permanently mounted on a really heavy tripod, had to be filled with liquid nitrogen before use, and sounded like a jet engine when operating, probably because of the large rapidly rotating mirror, and images were displayed on a separate oscilloscope like viewing device and captured with a Polaroid camera. (Images are of the actual device I used and were provided me by the Science museum at University of Oslo for identification).

 

 

 

[Nate]

Cool shots @otoienI love my thermals, so much fun. I have a Flir C2, Pulsar Quantum XQ23V, and a Pulsar Helion XP50. I'm always checking out wildlife at night.

[lukaszgryglicki]

I also enjoy my FLIR E75, it is 320x240 - also low res.

[Fandyus]

It's a shame these cameras seem to have such bad, noisy sensors. Imagine a camera like this, except it has proper 4K resolution. Not sure how wide-aperture of a lens you would need to compensate for diffraction but having such a camera for experiments would be priceless. The first thing I'd like to do is take a picture with and without a lightsource, then subtract them to remove the ever-present LWIR incandescence. I could then see how absorbent different materials are. The world would definitely look very alien.

[Nate]

 

@FandyusLight sources have no effect on thermals, just the heat an object gives off.

 

[Stefano]

It's more complex than that. A LWIR camera only sees light, you can't directly "see" heat. If you illuminate something with a LWIR light source, a thermal camera will see the blackbody radiation ("incandescence") and the reflected light. If the illumination is intense enough, you will also heat up the subject, so the amount of blackbody radiation will be greater.

 

This effect starts to be noticeable in the MWIR band, as Andy has shown and explained: 

Taking purely reflected photos past ~2-3 μm is not as simple as with shorter wavelengths.

[Andy Perrin]

Nate, that’s not totally true. Objects both emit and reflect LWIR. However the emitted light is very strong and usually overpowers the reflected light, except in the case of metals (which you can see in the photo of the teapot). I do not think you would have much luck subtracting off the emitted light because the emitted light is so strong that when you subtract it the resulting signal would be quite noisy. There is also the issue that shinning a LWIR source tends to change the temperature which changes the brightness of the emission, so simple subtraction would only work in the case of a flash (where the burst of light does not have time to change the temperature). This is also an issue for MWIR photos, and it’s one reason I haven’t used my MWIR camera much - the other reason being the weight making it hard to maneuver. 
 

ETA: stefano replied before I finished typing! 

[Stefano]

9 minutes ago, Andy Perrin said:

ETA: stefano replied before I finished typing! 

Ops, sorry. Well, it's surprising how similar our posts are. We confirmed each other.

[Andy Perrin]

I got that heavy tripod and gimbal lately, I may be able to do some more MWIR soon. 

[otoien]

Thanks for the comments. Except for the C2, quite a price tag on those devices!  With the older devices (the Agema 470 Pro has "Image Storage: 3.5″ floppy" !), one wonder how much behind they are technologically.  The Agema images do not look that much better than the  Seek device? ( https://www.x20.org/product/agema-thermovision-470/  )    Image sensing technique has come a long way in the visible spectrum since I used a Sony with floppy disk...  but I assume that with a Peltier controlled sensor, noise and calibration accuracy at lower temperatures will be much better.  Of course the James Webb telescope (0.6 to 28.5um) tops the price tags among LWIR capable devices...

 

[Andy Perrin]

The Adema is certainly not a good thermal camera by present standards as far as resolution goes, although I think its temperature accuracy may be competitive or better due to the very high sensitivity of those single-pixel sensors compared to microbolometers. 
 

The point of buying one was to get a camera that works in the MWIR range (2000-5000nm) rather than the LWIR (8-14 micron) range. I have several LWIR cameras already. MWIR is an unexplored realm that does not behave like anything else — it gets used in FTIR spectroscopy precisely because many materials have unique MWIR spectral “fingerprints” that can be used to identify them. 

[Nate]

Thanks Andy and Stefano for the info, I guess I have more to learn about LWIR. I do notice a lot of reflection especially with types of aluminum and glass objects

[Doug A]

Neat images @otoien. A whole different world. The technology has progressed greatly.

 Thanks for sharing,

Doug A

 

 

[otoien]

Thanks for the comment Doug and happy new year.