[curioushacking]

I worked for a number of years on making invisible fiducials that can appear only in infrared, and am one of the chief inventors on 3M's smart code. The idea was that on any retroreflective surface you can place this fiducial sticker and relay some information. We were originally looking at approximately 64 bits of information. This isn't a ton, but we thought it a good balance of error correction, and module (the pixels in the code) size.

At least from an IR perspective, it was generally loved by nearly everyone we spoke to, but there was no takers in the end due to the IR requirement and such cameras not being everywhere yet.

Here is a link to some of our first work. That picture of a stop sign is our first prototype with hand cut special film.

https://www.businessinsider.com/3m-hides-tech-in-sides-to-he...

[TeMPOraL]

Nice! Thanks for sharing! Didn't realize 3M was working in this space (but then again, whenever I ask or check if 3M is working on $randomThing, it turns out they do; it's a real-world ACME).

> but there was no takers in the end due to the IR requirement and such cameras not being everywhere yet

I wonder why that's the case. What kind of IR camera it required? I was under the impression that turning a regular camera into an IR one was just a matter of digging out its IR filter and replacing it with a visible light filter. Or did it require the kind of cameras that are used in thermal imaging? Unfortunately, I don't really know what the technical and business challenges are for ubiquitous IR. Could you share some information about it?

[curioushacking]

We could tune the material to whatever wavelength we wanted, but for ours we targeted above 850nm as that was a common filter. Regarding the actual camera to IR, you are right. Even the front facing camera on a iPhone is sufficient to read them.

Many cars use front facing cameras that with minimal adjustment could read at the proper wave lengths, but one issue for a lot of vehicles right now is that the windshield has an IR filter to minimize heat and interior damage. For cameras behind the rear view mirror, the standard windshield creates an issue. Windshields with a small cut of the film would be sufficient, but they are not manufactured to my knowledge.

For general fiducials not related to these, I had hoped to put them everywhere. Think even hidden everywhere and read by phones. But at least for a while I think the read facing cameras on phones will continue to have the filter and using the phone backwards with the front facing camera is awkward.