4 ms·

Laser technique measures distances with nanometre precision

39 points by westurner 2y ago

westurner 2y ago
> optical frequency comb "113 km absolute ranging with nanometer precision" (2024) https://arxiv.org/abs/2412.05542 https://arxiv.org/abs/2412.05542 : > two-way dual-comb ranging (TWDCR) approach > The advanced long-distance ranging technology is expected to have immediate implications for space research initiatives, such as the space telescope array and the satellite gravimetry
- mikewarot 2y ago
  Note that the precision is very good, however the accuracy is nowhere near as close (fractions of a metre) in the atmosphere, due to the variable refractive index of air. Long term averages can help, of course.
  - Aurornis 2y ago
    They talk about this technique for ranging between satellites, which wouldn't have to deal with atmospheric conditions. For ranging in an atmosphere they suggest dual-comb spectroscopy or two-color methods to account for the atmospheric changes.
    - westurner 2y ago
      From https://news.ycombinator.com/item?id=42330179 https://news.ycombinator.com/item?id=42330179 .. https://www.notebookcheck.net/University-of-Tokyo-researchers-prototype-optical-measurement-of-blood-pressure-and-glucose-levels.920305.0.html https://www.notebookcheck.net/University-of-Tokyo-researcher... : > multispectral [UV + IR] camera ... optical, non-contact method to detect [blood pressure, hypertension, blood glucose levels, and diabetes]." [ for "Non-Contact Biometric System for Early Detection of Hypertension and Diabetes" https://www.ahajournals.org/doi/10.1161/circ.150.suppl_1.4131796 https://www.ahajournals.org/doi/10.1161/circ.150.suppl_1.413... ] >> "Tongue Disease Prediction Based on Machine Learning Algorithms" (2024) https://www.mdpi.com/2227-7080/12/7/97 https://www.mdpi.com/2227-7080/12/7/97 : >>> new imaging system to analyze and extract tongue color features at different color saturations and under different light conditions from five color space models (RGB, YcbCr, HSV, LAB, and YIQ). [ and XGboost ]
sitkack 2y ago
I am only two pages in, but I want to say this paper is very well written. People should give reading it a try reading (with LLM assistance). If this technique could be adapted to existing optical fiber infrastructure, we could see the effects of fiber optic cable stretch and deformation in realtime.
kragen 2y ago
"Vast" really shouldn't have been eliminated from the title, because interferometers have been measuring distances with nanometer precision since even before there were lasers, and lasers have been used in interferometers since the first laser in 01960. Victorian-era interferometers, commonly used for grinding telescope mirrors, could only measure distances of a few meters with precision in the hundreds of nanometers. However, laser interferometers were already quite good; LIGO, most famously, detected gravitational waves by measuring strains of around 10⁻²⁰ over a distance of 1120 km, which works out to a change in distance of less than 0.000012 nanometers, much less than the width of a proton. The news here actually seems to be that "A new way to gauge distance using lasers can measure lengths of more than 100 kilometres ... To continue reading, subscribe today with our January sale." So, uh, I don't know, maybe the reporter wasn't familiar with LIGO and thought that nanometer-precision interferometry over kilometers was new? Sitkack, you say there's a paper somewhere?
- stavros 2y ago
  Oooh it's the guy with octal years!
  - greenbit 2y ago
    Noticed that too, but it has a '9' in it. Best guess is, he's not about to let the Y10K problem catch him napping.
    - __MatrixMan__ 2y ago
      It's kind of silly, but I do like the philosophy behind it: https://longnow.org/ideas/long-now-years-five-digit-dates-and-10k-compliance-at-home/ https://longnow.org/ideas/long-now-years-five-digit-dates-an...
      - cryptonector 2y ago
        See The Long Now Foundation.
      - 2y ago
jiveturkey 2y ago
anyone have a sense of whether this will make a difference for small distances as seen in construction and small parts (less than car-sized) non-optical manufacturing? i feel like the precision available today, with handheld laser rules and what-not, are already cheap and accurate enough.
- itishappy 2y ago
  Traditional interferometry already achieves sub-nanometer precision. This is already many orders of magnitude more precise than most non-optical manufacturing processes, so I agree with your analysis!
- kragen 2y ago
  It will not, or even for less-than-car-sized optical manufacturing.

39 points by westurner 2y ago

> optical frequency comb "113 km absolute ranging with nanometer precision" (2024) https://arxiv.org/abs/2412.05542 https://arxiv.org/abs/2412.05542 : > two-way dual-comb ranging (TWDCR) approach > The advanced long-distance ranging technology is expected to have immediate implications for space research initiatives, such as the space telescope array and the satellite gravimetry

mikewarot 2y ago
Note that the precision is very good, however the accuracy is nowhere near as close (fractions of a metre) in the atmosphere, due to the variable refractive index of air. Long term averages can help, of course.
- Aurornis 2y ago
  They talk about this technique for ranging between satellites, which wouldn't have to deal with atmospheric conditions. For ranging in an atmosphere they suggest dual-comb spectroscopy or two-color methods to account for the atmospheric changes.
  - westurner 2y ago
    From https://news.ycombinator.com/item?id=42330179 https://news.ycombinator.com/item?id=42330179 .. https://www.notebookcheck.net/University-of-Tokyo-researchers-prototype-optical-measurement-of-blood-pressure-and-glucose-levels.920305.0.html https://www.notebookcheck.net/University-of-Tokyo-researcher... : > multispectral [UV + IR] camera ... optical, non-contact method to detect [blood pressure, hypertension, blood glucose levels, and diabetes]." [ for "Non-Contact Biometric System for Early Detection of Hypertension and Diabetes" https://www.ahajournals.org/doi/10.1161/circ.150.suppl_1.4131796 https://www.ahajournals.org/doi/10.1161/circ.150.suppl_1.413... ] >> "Tongue Disease Prediction Based on Machine Learning Algorithms" (2024) https://www.mdpi.com/2227-7080/12/7/97 https://www.mdpi.com/2227-7080/12/7/97 : >>> new imaging system to analyze and extract tongue color features at different color saturations and under different light conditions from five color space models (RGB, YcbCr, HSV, LAB, and YIQ). [ and XGboost ]

sitkack 2y ago

I am only two pages in, but I want to say this paper is very well written. People should give reading it a try reading (with LLM assistance). If this technique could be adapted to existing optical fiber infrastructure, we could see the effects of fiber optic cable stretch and deformation in realtime.

kragen 2y ago

"Vast" really shouldn't have been eliminated from the title, because interferometers have been measuring distances with nanometer precision since even before there were lasers, and lasers have been used in interferometers since the first laser in 01960. Victorian-era interferometers, commonly used for grinding telescope mirrors, could only measure distances of a few meters with precision in the hundreds of nanometers. However, laser interferometers were already quite good; LIGO, most famously, detected gravitational waves by measuring strains of around 10⁻²⁰ over a distance of 1120 km, which works out to a change in distance of less than 0.000012 nanometers, much less than the width of a proton. The news here actually seems to be that "A new way to gauge distance using lasers can measure lengths of more than 100 kilometres ... To continue reading, subscribe today with our January sale." So, uh, I don't know, maybe the reporter wasn't familiar with LIGO and thought that nanometer-precision interferometry over kilometers was new? Sitkack, you say there's a paper somewhere?

stavros 2y ago
Oooh it's the guy with octal years!
- greenbit 2y ago
  Noticed that too, but it has a '9' in it. Best guess is, he's not about to let the Y10K problem catch him napping.
  - __MatrixMan__ 2y ago
    It's kind of silly, but I do like the philosophy behind it: https://longnow.org/ideas/long-now-years-five-digit-dates-and-10k-compliance-at-home/ https://longnow.org/ideas/long-now-years-five-digit-dates-an...
    - cryptonector 2y ago
      See The Long Now Foundation.
    - 2y ago

jiveturkey 2y ago

anyone have a sense of whether this will make a difference for small distances as seen in construction and small parts (less than car-sized) non-optical manufacturing? i feel like the precision available today, with handheld laser rules and what-not, are already cheap and accurate enough.

itishappy 2y ago
Traditional interferometry already achieves sub-nanometer precision. This is already many orders of magnitude more precise than most non-optical manufacturing processes, so I agree with your analysis!
kragen 2y ago
It will not, or even for less-than-car-sized optical manufacturing.