Interferometer Device Sees Text from a Mile Away
30 comments
·May 10, 2025IAmBroom
dekhn
We are in the middle of a renaissance of image processing across a wide range of fields. Many of the previous limits are being smashed by using new materials and algorithms. See https://en.wikipedia.org/wiki/Fourier_ptychography for an example
kevmo314
That's how night mode works on Pixel phones, right? I believe it takes a few images in rapid succession and took advantage of the noise being random which meant a high quality image under a noisy sensor with some signal processing.
Calwestjobs
some phones shine IR floodlight, too.
hammock
>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.
You ought to read Tom Wolfe’s “the right stuff” asap if you haven’t already
perihelions
- "Flash the laser at the same time as the image, scan the laser-illuminated spot, calculate the perturbance, and reverse-filter the image"
That's also how some adaptive optics work in astronomy,
embwbam
The adaptive optics system for the DKIST solar telescope actually deforms each point of the mirror at 60Hz or something to do wavefront correction!
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hammock
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
27theo
> The team demonstrated that this intensity interferometer can image millimeter-wide letters at a distance of 1.36 km
abcd_f
Letters were 8 mm.
> To demonstrate the system’s capabilities, the team created a series of 8-mm-wide targets, each made from a reflective material and imprinted with a letter.
Calwestjobs
intensity interferometer means it interferometers intensity of light.
imaging technologies you mistook for imagination technologies and their gpu inside of a sega dreamcast or iphone, ipad,...
1.36 km = 0.85 miles
admash
Presumably this could be used for color imaging by using lasers of different wavelengths?
jdiff
I believe it'd be pretty wonky coloring, or at least it could be, since it'd be capturing snapshots of individual frequency responses. If something is visibly green, reflecting across most of the greenish areas of spectrum, but happens to absorb the exact frequency of the laser, it'd appear black when imaged this way. Or at least not green.
erikerikson
How does this compare to the state of the art?
knotimpressed
I wonder if the requirement to rotate the target is inherent, or if it could be optimized away eventually?
stevemadere
I suspect this was an easy way to test it without having to build a rotatable optical bench.
A practical device may be an array of light sources and telescopes on a rotating mount or a set of moveable mirrors that achieve the same effect.
nkrisc
If it is required, then in a real application you could just rotate the laser array instead.
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Noumenon72
I also wonder about the requirement for the letters to be made of reflective material.
1minusp
i think the applications to spy-craft could be quite interesting here. Something for the next mission impossible movie maybe?
codeulike
... but only if its written on shiny paper
ck2
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
vmh1928
Modulating a laser beam for communications is not new but this distance effort by amateurs doing a two-way voice transmission over 167km in New Zeland is pretty cool. This article also mentions a number of other laser communication long distance efforts.
https://www.modulatedlight.org/Modulated_Light_DX/MODULATED_...
IAmBroom
And the next will be when the amateur data links manage to noticeably heat the mirrors...
Calwestjobs
they will heat starlink first.
eesmith
People do use radio (though not optical) for Earth-Moon-Earth data links: https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Ear...
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.