Before flat screen technologies took over, we associate TV with the CRT. But there were other display technologies that worked, they just weren’t as practical. One scheme was the Nipkow disk, and [Bitluni] decided to build a working demonstration of how such a system works.
Essentially, there’s a spinning disk with a spiral pattern of holes in it. As the disk spins, a light behind it turns on or off. If you time everything right, you get an image that can move. This particular model uses stepper motors, which is a bit of a modern concession.
The result was actually much better than you might guess, but a far cry from a modern display device, of course. The screen material needed a little tweaking, but even the initial results were very impressive. If this were trying to be practical, it would probably require a bit more work on the light source and screen.
Interestingly, the Nipkow disk arrangement was just as suitable for scanning as displaying. Instead of a light behind the wheel, you simply used a light sensor. Of course, in practice, getting everything synchronized and mass-producing high-resolution sets would have been a tremendous challenge a century ago.
Not that people didn’t try. There were even color systems using mechanical wheels. In the 1930s, people were sure your TV would contain spinning disks.
The CBS color system was not based on the Nipkow principle.
But, that’s not why they are now called “see BS”!
B^)
Does the video say that’s the case? The article certainly doesn’t.
Very interesting project. I remember reading about the early attempts of producing a TV image. One thought though….with all the spinning LED displays that have been seen here on HD (and sold on a foreign sales site – “T”)… couldn’t a Nipkow Display be considered a relative to POV – Persistence Of Vision displays ? There seems to be some overlapping tech.
CRTs are POV too — the electron beam hitting the phosphors is conceptually no different from a stick with an LED on the end of it, swinging wildly
The phosphors in a CRT continue glowing after the electron beam hits them. POV does even out the brightness of the picture, but it’s not entirely POV.
Make the led bright enough and your eyes will take over for the phosphor layer since your retinal cells have their own refractory period. Although that might make it uncomfortable to watch lol.
HD (405 lines) mechanical TV mas actually a thing in the 1930’s, lookup Scophony TV or the Baird 240 line system.
… and TeKaDe’s mirror screw.
Doom on a Nipkow disk display, hmm. He might be the first to do that.
I love seeing old tech concepts recreated like this. Inspires me to dig through science magazines and newsletters from early 1990s. Thankfully there are great archives that provide such material.
I’m surprised a filament printer can produce nice round holes that small. I would’ve expected them to have to be drilled.
I’m even more surprised that the disc was printed at all. Not long ago a long playing record would have been the material of choice.
Reminds me of the German version of Mickey Mouse magazine.
They had printed a hoovercraft project using a record, a balloon and a spool of thread.
It was an issue of late 80s/early 90, I think. Back then, records were considered old junk.
Rightfully, I must admit. Considering the cheap record players of the time that ordinary people used.
They caused damage to the records. Better record players had fine needles and moving-coil system.
But even that couldn’t fix the bad musical taste of certain people (Volksmusik). ;)
Was it Duke Ellington who said,
“You can tell good music from bad music by listening to it.”?
A problem with implementing this as TV technology in the 1920s would have been how to synchronize the spinning disc with the incoming TV signal, since there was no way to buffer the incoming signal. I’m curious as to what solutions were proposed for this (but not curious enough to google it).
The TV signal has a short blank section before every line and between frames that the TV uses to synchronize its internal oscillator with a phase locked loop circuit. That’s how analog TV works – there’s no buffer either.
When the oscillator (or the disc) is running at almost the right speed, you can compare the start of frame pulses coming from the oscillator and the TV signal and do a bit of analog math: when the timing is exactly right the pulses cancel each other out, but if one is early or late then you get a positive or a negative pulse that tells the rest of the circuit whether to speed up or slow down. It eventually stabilizes to a small but constant offset and the picture stops jumping around.
Could’t you simply use mains synchronous motors (like in an electric clock)? That should provide the right frequency, phase could be made manually adjustable.
Mains is unreliable with way too much variation in frequency.
No it isn’t, as long as the sender and receiver are connected to the same grid.
However some active from of synchronization is to be preferred and would save the viewer from adjusting the device. See the link below for more information:
http://www.earlytelevision.org/Yanczer/motor_drive.html
The frequency and phase difference between parts of the grid is what determines the direction of power flow on the AC grid. Your television picture would be constantly drifting in and out view because of that.
There is a CBS spinning disk camera that was left on the Moon during Apollo exploration
The only disc that camera used was a color wheel, to create filed sequential color. Which is obvious when you look at the images of the Apollo 17 liftoff from the moon, you’ll notice the colorful specs, the side effects of fast moving object in a field sequential color system.
https://www.youtube.com/watch?v=9HQfauGJaTs
For more info about these cameras see this link:
https://www.nasa.gov/wp-content/uploads/static/history/afj/ap13fj/pdf-hr/90-apollo-tv-camera.pdf
How could it take off from the moon when we never landed there? Just kidding.
This article is a neat look at “Well we tried that.”
This technique is still being used in 2024 (and probably many more years) in DLP projectors.
The DLP micro mirrors can only produce mono picture so a colour-wheel is being used to filter a required colour from a white light source
Such fun, watching the modern guys bewildered by the history of the television system!
First off, as transmitted to the public, was the Baird System using Nipkow disk, 30 line vertical. Moving pictures, certainly, low definition, but you could build your own receiver at home. This was alternated with the all-electronic 405 line system.
It soon became obvious that the Baird mechanicals could not be much improved, but electronic one could.
So, in the late 1930s, we had 405/50 tv in London. Then the war started, and everything was closed down.
After the war, Europe opened up with 625/50, but UK kept on 405. Eventually all UK services by 1975 were on 625/50, PAL colour, and UHF.
Part of me wants to build a Nipkow disc serial terminal. This seems like the simplest low-tech display technology.