[HN Gopher] Battery-free wireless imaging of underwater environm...
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Battery-free wireless imaging of underwater environments
Author : rntn
Score : 49 points
Date : 2022-09-26 14:06 UTC (8 hours ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| isoprophlex wrote:
| > We use an underwater projector that transmits a 20 kHz
| sinusoidal acoustic signal (source level 180 dB re 1 uPa @ 1 m)
| on the downlink
|
| That sounds pretty abusive towards everything with ears and/or
| any kind of pressure sensitivity
| doodlebugging wrote:
| It a good bit lower than the energy level of a typical marine
| seismic airgun array which puts out (according to this source
| [0]) 243-249 dB re 1 mPa-m.
|
| [0] https://www.geoexpro.com/articles/2010/01/marine-seismic-
| sou...
|
| I agree that it sounds really obnoxiously loud though. There is
| a valid reason why marine seismic sources are tightly
| controlled and some have been banned. This makes old legacy
| data valuable for those companies that acquired before the
| bans.
| londons_explore wrote:
| And even at these regulated levels, there are lots of claims
| that things like whale beachings are caused by them...
|
| It's orders of magnitude higher than natural ocean sounds.
| doodlebugging wrote:
| That's true. It is very loud. I believe today that crews
| must have biologists on board monitoring marine mammal
| activity in the area and that acquisition must stop when
| animals enter the area. There are also seasonal
| prohibitions on activity in most areas to allow mating and
| calving.
|
| This is not enough and it doesn't address the louder sounds
| from submarine communications which are most likely to be
| the reason for most mammal groundings today.
|
| It is better than it was in the 70's and 80's though.
| People learned and they adapted, though not always
| willingly.
| swamp40 wrote:
| Reminds me of the deep-water drone video where a beautiful
| unknown species drifts into view and then is unceremoniously
| ripped to shreds by the drone's propulsion system.
| bad_alloc wrote:
| Do you have a link to that video?
| swamp40 wrote:
| https://youtu.be/BaX6BK66v9A?t=50
|
| Shredded at 1:12. Sad.
| swamp40 wrote:
| The transformation at 0:39 is also incredible.
| EricMausler wrote:
| Some takeaways:
|
| "Our method consumes five orders of magnitude less power than
| previously reported underwater wireless imaging systems"
|
| This is accomplished by harvesting energy from acoustics over
| time and then triggering a circuit to operate for a brief period
| before recharging.
|
| The method uses "acoustic backscatter" as a means of telemetry
| for sending the images
|
| The imaging is done with a HM01B0 from Himax Corporation. They
| capture 3 monochromatic images using red, green, and blue LEDs.
| Looking at the produced image given by example, I am not sure how
| accurate the coloring is, but the shape of the object is well
| defined on a centimeter scale.
|
| Distance between object and camera is under 3.5 meters. The
| distance they send the image also appears to be about 3.5 - 4
| meters. They mention a feasibility to send images over 40 meters
| with additional tooling.
|
| Device operates around 3.2 volts (triggered by a "super-
| capacitor" setup) until it depletes to 1.4 volts.
|
| Memory capacity is 12 kbs, and data transfer rate is capped at
| 1kbps due to the medium. They send one color at a time using
| 77-bit packets.
| isoprophlex wrote:
| I read this as "five orders of magnitude less power in getting
| data back up"; however note that they have to light up the
| sensor with very intense pressure waves to get power in and
| data back out.
|
| I'd love to be proven wrong tho
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(page generated 2022-09-26 23:02 UTC)