alt Hacker NewsInterferometer Device Sees Text from a Mile Away
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> The team demonstrated that this intensity interferometer can image millimeter-wide letters at a distance of 1.36 km
> He imagines that the remote-imaging system could have several applications, including monitoring insect populations across agricultural land.
“Insect populations” is a funny way to spell secrets. Jokes aside, it does seem like this could serve a wide range of non-espionage related use cases. Really cool.
That interesting article led me down a research rabbit hole of microwave maser inferometers and whether that could be an explanation for the controversial Havana Syndrome. And, having skimmed descriptions of historical SIGINT projects Buran[1] and Luch[2], and the theoretical advantages of such a system ... my curiosity in Faraday cages is renewed.
Lasers really are an underrated miracle. So many diverse uses for things that would be impossible without them.
And we are about to be saturated in them as soon as LiDAR full self driving goes mainstream
the website delights with the absence of ads throwing up into my eyes
My (mis?)understanding was that two receivers acting as an interferometer can only resolve things that are on a line parallel with the line between the receivers--so if the receivers are on a horizontal, then they can resolve left and right in their targets, but not up and down. But the images shown in the paper have more or less full 360 degrees resolution. Is that because they rotated the target? The paper says they did, but it's not clear how many increments of partial rotation they did--every 10 degrees, 20,...
If the target cannot be rotated, can the two (or more) receivers revolve around a central axis? If so, presumably one of the receivers could revolve around the other (fixed) receiver to the same effect.
Presumably this could be used for color imaging by using lasers of different wavelengths?
i think the applications to spy-craft could be quite interesting here. Something for the next mission impossible movie maybe?
the reflective material requirement seems to be a limiting factor, so most likely application would be license plate reading?? They didn't mention anything about moving targets, but I guess space debris is also moving so maybe as an added layer to LiDAR??
I wonder if the requirement to rotate the target is inherent, or if it could be optimized away eventually?
Except when it's raining
My favorite "lasers at distance" thing will be when amateurs can get a few photons back from the mirrors left on the moon
https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment...
Not quite there yet at the amateur level, private industry soon, but then there is the question of safety to air traffic.
Can you imagine the first moon data link? JWST has 8mbps
How does this compare to the state of the art?
... but only if its written on shiny paper
OK, this part was brilliant:
"To avoid this problem, the team divided their 100-milliwatt laser into eight beams. Each beam travels along a slightly different path through the turbulent atmosphere and thus receives a different random phase perturbation. Counterintuitively, this incoherent illumination makes the interference effects observable.
When I first started studying optical engineering, my teacher had worked on the first under-the-RADAR guidance system for bombers. He told lots of amusing stories, like how the pilots insisted on a manual override - so they "agreed" to provide a switch, noting to us manual piloting at near-treetop level and 1,000 ft/s is insane.
He taught us about the nominal amount of turbulence in the atmosphere, and that it limited space-based cameras to about half a foot resolution - a limit he said couldn't be broken. Therefore, license plates would never be readable from space...
Before I was out of grad school, they had broken it with laser techniques on nearby targets. Flash the laser at the same time as the image, scan the laser-illuminated spot, calculate the perturbance, and reverse-filter the image. A lot of processing (for that day), but it could be done back on Earth.
As you can see from the test images, the 8 lasers aren't enough to perfectly smooth out the noise. The noise is probably square-root-8 improved, so resolution should improve by a factor of not quite 3. Move those lasers slightly and repeat 12 times; you've improved resolution by 10. This is easy to do quickly; you should be able to read fine print held by a car passenger on the highway.