Here is an excellent in-depth explanation of the concept from one of my favorite educational YouTube channels - Technology Connections: https://youtu.be/v5OANXk-6-w

I just watched that and have to agree, an excellent in-depth explanation it was indeed, with a lovely demonstration.

A descendant of this guy is hard at work in theorem proving: http://www21.in.tum.de/~nipkow/

Is this a joke or is Tobias a (great) grandson of Paul Gottlieb's?

Not a joke. I asked him about that (quite) a few years ago, and he indeed is :-)

William Osman tried to build a mechanical display around these: https://www.youtube.com/watch?v=R96TtG5FCTU

He seems to really be overcomplicating its construction with all those fancy 21st century electronics when in reality you can build it with early 20th century materials.

I wonder if a camera obscura would be enough to create the focused image instead of having to bother with lenses.

Probably, but that would require even more light.

Set appropriate expectations before you watch this video, it was definitely educative and entertaining, but the emphasis is on 'tried'. I was a little disappointed that it didn't actually end up working.

Thanks for this, I have been trying to remember the term 'confocal microscopy' for a while. https://en.wikipedia.org/wiki/Confocal_microscopy

This is a really good short educational video about the invention of television:

https://www.youtube.com/watch?v=MyHAev_qJNU

This is very similar to the old fax machines, that had a needle over a rotating text on a wax cylinder and reproduced the needle up-down on the other end with a pen. Predated telegraph etc.

I don't understand why you have to approximate straight scanlines by using a fraction of a really large disk. What's the disadvantage in using a smaller disk and letting the scanlines be curved?

With the large disk, the difference between the (linear) velocities of different holes is smaller.

I would use a drum instead. You can make the scanlines near-perfectly linear if you look from a right angle.

Could it be possible to use this mechanism to create a type of X-ray or gamma ray camera? Perhaps using a lead disc.

The spelling of disk, with a K, intrigues me, since I was under the impression that disk-with-a-K was short for "diskette", meaning a circular spinning object protected inside an outer casing.

Circular flat objects are spelled disc, with a C.

Hence floppy disk, hard disk, but compact disc.

(MiniDisc is the only exception to this rule that I can think of, probably because it is a trade mark.)

Seems Wikipedia has a dedicated article on the subject!

https://en.wikipedia.org/wiki/Spelling_of_disc

Relevant bit:

> in the case of flat, rotational data storage media the convention is that the spelling disk is used for magnetic storage (e.g. hard disks) while disc is used for optical storage (e.g. compact discs, better known as CDs). When there is no clear convention, the spelling disk is more popular in American English, while the spelling disc is more popular in British English.

I should have known, Wikipedia knows everything.

I didn't know that disk = diskette was a British thing! And I am British. So I guess that makes sense.