How I built the world's first 3D ultrasonic scanner

https://www.alextoussaint.com/2021-04-28_How-I-built-an-ultrasonic-3d-scanner.html

by belzebalex • 5 years ago

152 44 5 years ago

wyager• 5 years ago

There have been some projects to make “sonic cameras” using MEMS mic arrays that this reminds me of. https://hackaday.com/2020/08/10/acoustic-camera-uses-many-ma...

belzebalex15• 5 years ago

The maths is exactly the same, except that the beamforming is at the reception rather than at the emission. But it works based on the same principle.

rescbr• 5 years ago

Hah! Back in my undergrad days I’ve thought about doing exactly this, but I couldn’t figure out the beamforming part, so I just measured distances in (microcontroller) software by correlating transmitted x received waveforms.

Awesome project! I’m happy the author figured it out! I feel vindicated :)

belzebalex15• 5 years ago

Thank you!I've been helped a lot by how technology changed for the past few years (lots of good resources online, was able to do simulations easily, MCU programming a lot easier, etc).

tomcam• 5 years ago

Amazing. I was literally working in a factory at that age

abductee_hg• 5 years ago

well, you sir, are the first. except maybe those lamers: https://en.wikipedia.org/wiki/Medical_ultrasound

vlovich123• 5 years ago

The title in the submission is inaccurate & not actually the title of the article. The missing bit:

that works in the air, using off-the-shelf components (< $100).

b0tzzzzzzman• 5 years ago

Have you seen the way lasers are used to do this? NDT or non destructive testing has use dual laser systems to create ultrasound for several decades. Check it out if you are interested.

I can try to find that papers if you would like.

belzebalex15• 5 years ago

I think one of the subjects of my exam for entering engineering schools (a thing we do in France) was about that.

Would really like to see papers on the subject, because I don't really understand how you can use lasers in opaque materials. Will also look at my test to see if it's really about that.

littlestymaar2• 5 years ago

I think one of the subjects of my exam for entering engineering schools (a thing we do in France) was about that.

Cool. For which school was it? And Which year? (I'd like to get the subject and read it actually)

danwills• 5 years ago

Fascinating! Awesome project. Interference of waves seems to be such a fertile ground for all sorts of unexpected powerful possibilities.

raverbashing4• 5 years ago

Interesting, but yeah, he fought way too hard with the analog part driving the transducers

I get it, it's a hobby project, but I feel the knowledge of analog electronics is getting lost in a way (and yes the analog people are the worse at explaining things - I think I saw YT videos more informative than whole university courses)

belzebalex15• 5 years ago

Author here. It's all digital (square waves!).

There were definitely well-known circuits for driving transducers, but I had to improvise to make a circuit small and simple enough to build 100 of them.

Building new circuits requires tinkering and many tries, regardless of the builder's knowledge.

raverbashing4• 5 years ago

well-known circuits for driving transducers, but I had to improvise to make a circuit small and simple enough to build 100 of them

Yes, maybe an Opamp that works at 40V could have worked (with an appropriate feedback config), but your end result looks ok. I'm just saying that putting the transducer in the emitter was a non-starter (as you correctly pointed out)

Building new circuits requires tinkering and many tries, regardless of the builder's knowledge.

Absolutely, I'm not denying it :) It's a great job nonetheless

vanderZwan• 5 years ago

If it's so easy, why hasn't anyone done it before?

Medical 3D ultrasounds are a thing:

https://en.wikipedia.org/wiki/3D_ultrasound

That doesn't take away anything from how cool this project is though!

belzebalex15• 5 years ago

I guess that the main option is the second one. Lidars, once they are solid-state and cheaper will be a better alternative (smaller, more precise and much faster).

The first option isn't the good one. Ultrasounds are already used in car parking assists and people trying to improve them would have gone the same route as I did.

jiofih• 5 years ago

It’s a lot easier when the waves are propagating in mostly liquid. Like a sonar.

minipci13213• 5 years ago

Great accomplishment, but people were building 3D ultrasonic scanners back in 80-ies, for much less than $100:

[didn't read your article, your claim has put me off, sorry]

-- use an electric spark gap as the wideband acoustic source

-- use 3 simple electret mikes on 3 axes. Mikes don't need to be high quality (spark intensity can always be raised as necessary), so they were hand-assembled using metallised mylar film (used nowadays to pack some food, or ESD-sensitive electronics components).

The rest was data processing.

belzebalex15• 5 years ago

Very interesting! Do you have any links for me to learn more?

There are a few limits on what you can scan with only 3 mics. I detail everything in my article. Really suggest you read it.

minipci13213• 5 years ago

I only quickly checked and found this:

https://rusneb.ru/catalog/000224_000128_0000488231_19751015_...

-- click on "Skachat' PDF" (second from the top on the left). Unfortunately it is in Russian, not sure whether English translation exists.

This patent seems only for (X,Y) coordinate capture, but the same authors later worked on 3D setups as well.

EDIT: let me know if you need help with translation

acomjean• 5 years ago

Reminds me of phased array radars. Where they form an array of transmitters into a moveable “beam”

https://en.m.wikipedia.org/wiki/Phased_array

Radar is at its simplistic sensing a pulse out and listening for a return. But then the engineers wanted more.. of course home radar would not be really safe.

Cool project by the way.

belzebalex15• 5 years ago

It is exactly what it is, except I used ultrasounds (40khz, easy to work with) instead of electromagnetic waves.

amelius3• 5 years ago

I hated using a Chinese company for a job that could be done in France, but no local companies were offering the same service.

They exist, except they are more pricey.

belzebalex15• 5 years ago

Would you have any links please? I didn't see any that did small development batches for a price lower than 200 EUR.

amelius3• 5 years ago

https://pcbshopper.com/

nerdbeere• 5 years ago

https://aisler.net/

they definitely aren’t as cheap as Chinese offers but I always found them to be reasonably priced. They manufacture in Germany.

Aeolun• 5 years ago

Not sure about the first, but it is really cool regardless. I tried doing a similar thing once upon a time with RFID (SAR), but I couldn’t figure out how it would work.

This seems even lower level, since I was basically using off the shelf components, and you built the whole thing yourself!

Really cool.

sorenjan• 5 years ago

Phased array ultrasonics[0] and Multibeam echo sounding[1] has been around for decades[2]. This project in particular is an example of what's called an air coupled ultrasonic phased array. It's an interesting project, but it's not first. Congrats on making it happen though, and thanks for the write up.

[0] https://en.wikipedia.org/wiki/Phased_array_ultrasonics

[1] https://en.wikipedia.org/wiki/Multibeam_echosounder

[2] https://patents.google.com/patent/US5675552

belzebalex15• 5 years ago

Author here, the title is a bit misleading. In the article, I specify that it's the first 3d ultrasonic scanner (of my knowledge) that works in the air.

How I built the world's first 3D ultrasonic scanner

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