Infrared cameras for the masses

Well that’s interesting. It seems, mobile phone cameras are actually sensitive to near-infrared light. It really does work. I tried it with my own. Near-IR shows up as a purplish colour. You can see it on anything hot enough to glow or almost glow.

It’s also evidently the reason why any pictures taken on phones involving fire look bleached out and over-whitened. The purple colour would blend with the orange of the flames. Which is, interestingly, a similar effect to the way optical brighteners work in washing powder. But I digress…


This image is of an electric hob, just reaching the temperature where it would glow red. It’s on unapproved personal loan (in other words, I yoinked it) from Built on Facts, where you can read more about all of this…

Interestingly, it kinda makes sense. Without going into the gory details of the photoelectric effect, the sensors in most phone cameras use Charge-Coupled Devices (CCDs). The simplified picture is that photons hitting the CCD array cause charges to build up in different places. Those charges are proportional to the intensity of the light hitting them. Electronics essentially convert those charges into voltages and store the whole thing as a 2-dimensional image. Ok, so that’s very much simplified, but like I said, I don’t want to go into the details right now.

CCDs are used in a lot of places, incidentally — including telescope optics where they’re used to pick up frequencies from infrared right up to UV. While trying to do astrophotography with a phone camera is just plain laughable, I can’t help but wonder what the sensitivity range is on them. I might have to do some experimentation…

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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