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Comment by shaftway | Hacker News Reader

I've always wished that you could get a separate IR channel in phone cameras. Combine this with IR ink or IR channels on video feeds and you've got invisible QR codes. I suspect there's huge potential for being able to point your phone at content and have it magically link to data about the product / show / ad / event / whatever.

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Phone cameras can see in IR. A classic trick to test if your TV remote is working is to look at the LED through a digital camera while pressing a button. Try it right now if you don't believe me.

What's missing is screens which can display meta information in the IR channel. I say we call the image format IRGB.

Yeah, I use it to see if my old remotes' batteries are dead.

They can see in IR, but they can't distinguish it from other light. Maybe that's good enough.

iPhones have IR filters over them so that doesn't work anymore unfortunately.

On my iPhone 7 at least, the rear camera seems to have an IR filter but the front one does not (or perhaps it has a filter but is less effective). So I can still test remotes in 'selfie' mode.

Doesn’t FaceID use structured IR light? If so, at least one of the cameras won’t have a filter.

The front camera usually doesn't filter IR.

They might be sensitive to IR without sufficient filtering but they're not selective to it, I think the idea here is something like a IR,R,G,B pixel format. Maybe you could get military interest in it (digital Aerochrome).

Also a good way to detect hidden surveillance cameras at night.

More generally, this problem is called Optical Camera Communication (OCC).

One of the more interesting things you can do is to exploit the rolling shutter readout method of consumer CMOS sensors to recover information with a high temporal resolution. By modulating the backlight of a video display or any other kind of wide-area light, you can transmit information optically to the phone in a way that's invisible to the user.

I'm not aware of any commercial applications of such tech, but there are enough keywords in this post to find a few research papers on the topic.

Great, now Facebook has yet another channel of data to mine your pictures for…

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