How is the image focused and not a big blur?
A laser pointer at 2B FPS [video]
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Re: A laser pointer at 2B FPS [video]
#52[dead]
Re: A laser pointer at 2B FPS [video]
#53Tl:dw for how this works: He scans one line at a time with a mirror into a photomultiplier tube which can detect single photon events. This is captured continually at 2MSample/s (2 billion times per second: 2B FPS) with an oscilloscope and a clever hack. The laser is actually pulsing at 30KHz, and the oscilloscope capture is synchronized to the laser pulse. So we consider each 30KHz pulse a single event in a single p…
Yup, this technique also allows oscilloscope capture signal with frequency higher than their Nyquyst bandwidth.
The downside is it only works with repeative signal.
Re: A laser pointer at 2B FPS [video]
#54The triggering scheme is completely brilliant. One of those cases where not knowing too much made it possible, because someone who does analog debug would never do that (because they would have a 50k$ scope!.
Does anyone have a $50,000 scope they could just give to this dude? He seems like he would make great use of it.
I bet we can find 50,000 people with one dollar to give. Let's make this happen HN!
Re: A laser pointer at 2B FPS [video]
#55Tl:dw for how this works: He scans one line at a time with a mirror into a photomultiplier tube which can detect single photon events. This is captured continually at 2MSample/s (2 billion times per second: 2B FPS) with an oscilloscope and a clever hack. The laser is actually pulsing at 30KHz, and the oscilloscope capture is synchronized to the laser pulse. So we consider each 30KHz pulse a single event in a single p…
Good explanation. One detail though: it is one pixel at a time, not one line at a time. Basically does the whole sequence for one pixel, adjusts mirror to next one, and does it again. The explanation is around the 8 minutes mark. Just want to make it clear that in any one instant, only one pixel is being recorded. The mirror moves continuously across a horizontal sweep and a certain arc of the mirror's sweep is local…
One piece I'd like to see more clarification on is, is he doing multiple samples per pixel (like with ray tracing?). For his 1280x720 resolution video, that's around 900k pixels, so at 30Khz, it would take around 30s to record one of these videos if he were to doing one sample per pixel. But in theory he could run this for much longer and get a less noisy image.
I find it interesting that a project like this would easily be a PhD paper, but nowadays Youtubers do it just for the fun of it.
Re: A laser pointer at 2B FPS [video]
#56The triggering scheme is completely brilliant. One of those cases where not knowing too much made it possible, because someone who does analog debug would never do that (because they would have a 50k$ scope!.
Does anyone have a $50,000 scope they could just give to this dude? He seems like he would make great use of it.
Honestly I think if we each wrote a nice personal letter to Keysight they’d probably gift him one in exchange for the YouTube publicity. Several other electrical engineers on YT get free $20-50k keysight scopes not just for themselves, but once a year or so to give away to their audience members.
And yes, this person could make use of it. His videos are among the highest quality science explainers - he’s like the 3B1B of first principles in physics. Truly a savant at creating experiments that demonstrate fundamental phenomena. Seriously check out any of his videos. He made one that weighs an airplane overhead. His videos on speed of electricity and speed of motion and ohms law are fantastic.
Re: A laser pointer at 2B FPS [video]
#57I'd like to see this with the double slit experiment
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Re: A laser pointer at 2B FPS [video]
#58I'd like to see this with the double slit experiment
It would look something like this[1] except with slower visual propagation.
Note that this camera (like any camera) cannot observe photons as they pass through the slits -- it can only record photons once they've bounced off the main path. Thus you will never record the interference-causing photons mid-flight, and you'll get a standard interference pattern.
[1]: https://www.researchgate.net/figure/The-apparatus-used-in-th...
Re: A laser pointer at 2B FPS [video]
#59I'd like to see this with the double slit experiment
AlphaPhoenix mentions in the description that he wants to try and image an interference pattern, and it seems possible.
Though it wouldn't really be showing you the quantum effect; that's only proven with individual photons at a time. This technique sends a "big" pulse of light relying on some of it being diffusely reflected to the camera at each oscilloscope timestep.
Truly sending individual photons and measuring them is likely impractical as you'd have to wait for a huge time collecting data for each pixel, just hoping the photons happens to bounce directly into the photomultiplier tube.
Re: A laser pointer at 2B FPS [video]
#60Tl:dw for how this works: He scans one line at a time with a mirror into a photomultiplier tube which can detect single photon events. This is captured continually at 2MSample/s (2 billion times per second: 2B FPS) with an oscilloscope and a clever hack. The laser is actually pulsing at 30KHz, and the oscilloscope capture is synchronized to the laser pulse. So we consider each 30KHz pulse a single event in a single p…
Good explanation. One detail though: it is one pixel at a time, not one line at a time. Basically does the whole sequence for one pixel, adjusts mirror to next one, and does it again. The explanation is around the 8 minutes mark. Just want to make it clear that in any one instant, only one pixel is being recorded. The mirror moves continuously across a horizontal sweep and a certain arc of the mirror's sweep is local…
And the reason it matters that this is a single pixel at two billion times per second is that we can hypothetically stack many of these assemblies on top of each other and get video of a single event that is not repeatable.