Electronics > Projects, Designs, and Technical Stuff
Electrostatic vidicons?
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Dave92F1:

--- Quote from: chris_leyson on April 08, 2019, 06:39:09 pm ---A long time ago the BBC had a GB patent on using fractal scanning using space filling curves, either Hilbert or Peano curves. The idea behind it was that you could take a high resolution Hilbert scanned image and still display it lower resolution Hilbert scanned monitor, and vice versa probably. BBC R&D report here http://downloads.bbc.co.uk/rd/pubs/reports/1991-04.pdf

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A fascinating idea!! In principle that ought to work, tho I'm not sure it's at all practical. I downloaded the report. I can't immediately think of a way to combine that with an efficient coding scheme (to make it practical). Modern video codecs have a practical (well, it works) way of doing that - for example https://en.wikipedia.org/wiki/Scalable_Video_Coding (I know most of the inventors of that - very bright people.)


--- Quote from: CatalinaWOW on April 08, 2019, 08:52:44 pm ---Interesting concept, and a simulation might work if played back on a high frame rate monitor.
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Yes, also many "gaming" monitors are on the market that do up to 240 Hz frame rate. I don't have one, but I could do a simulation with a 30 Hz source video of something very slow (airplanes moving around on an airport, clouds moving across the sky), then speed it up and try coding it with the random scanning.


--- Quote ---I think your idea would be more productive if instead of random scan you used motion detection to prioritize scan areas, much as is done in several video compression schemes.
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For sure that would be something to try if I were interested in something practical. But I'm not - I just want to see what it looks like. It's a hobby project.

I got interested in this 20 years ago when I was involved in video coding standardization (I was on the H.264 standards committee). There's this tradeoff between spatial and temporal video resolution, and this seems like an interesting (but probably impractical) way of making that tradeoff. Anyway, I always wanted to see what it would look like, then saw old electrostatic CRTs on eBay (bought a few), then decided I could try it if I had an electrostatically deflected vidicon...


--- Quote ---All of this interacts with the human vision system in ways I can't even guess about, but you might be on to something.

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Yes, indeed. That's what I want to see.
Richard Crowley:

--- Quote from: chris_leyson on April 08, 2019, 06:39:09 pm ---A long time ago the BBC had a GB patent on using fractal scanning using space filling curves, either Hilbert or Peano curves. The idea behind it was that you could take a high resolution Hilbert scanned image and still display it lower resolution Hilbert scanned monitor, and vice versa probably. BBC R&D report here http://downloads.bbc.co.uk/rd/pubs/reports/1991-04.pdf

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I see that as a very crude "cave-man era" broad-concept scheme precursor of what modern video codecs do these days in software.
james_s:

--- Quote from: Dave92F1 on April 08, 2019, 05:48:04 pm ---
--- Quote from: james_s on April 08, 2019, 05:33:54 pm ---If it was random I think you'd end up with large variations in brightness across different portions of the screen. It would likely end up looking like an image projected on a pile of yarn.

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If the bandwidth were too low, yes. If you do it fast enough, the Law of Large Numbers should kick in and average things out. I think.

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I think you'd have to go really, *really* fast before that worked.
chris_leyson:
The BBC space filling curve scanning idea was maybe GB2193411A or US4843468 or a closely related patent. The idea that the patent was putting across was that you could display the fractal image use a lower bandwith magnetic scanning system because the beam path doesn't change but you just loose a bit of spatial resolution. I think the patent also implied that you could use existing raster scan coils. Hmmm.. I've just given a Vectrex console a funny look  ;)
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