Mirror Drum

[peter scott]

The seller describes it as 27 line but I counted 30 mirrors.

http://www.ebay.co.uk/itm/Baird-televisi...2067137202?&_trksid=p2056016.l4276



Peter

[Craig]

I think this pre-dates Baird. It is identical to the 30-mirror scanner that was used by Lazare Weiller in 1889. If you look carefully each mirror is at a slightly different angle (most easily seen on one of the pictures where it goes from maximum angle to minimum) so a single spinning mirror also does horizontal scan too.

Needs very accurate machining to register the mirrors.

Pretty darned rare.

Craig

[Murphyv310]

Rare isn't the word. could well be a one off.

[Craig]

These very early systems did a vertical raster, rather than horizontal. So the slow scan direction was horizontal.

There were all sorts of weird and wonderful systems pre CRT. The Eidophor projection TV (also used for cinema) used an electron beam to write a raster on a film of oil. The optical diffraction pattern from that was the projected image. Because of heating of the oil film the (concave) disc continuously rotated, and a doctor blade presented a uniform thickness of virgin oil film to the electron beam. They even had a rotating colour filter wheel synchronised to the scan to produce frame sequential colour.

Back in the mid 80's I developed a not dissimilar system for BAe https://www.flightglobal.com/FlightPDFAr...201593.PDF based on solid state scanning.

Astonishingly there are still one or two of them still in use, in spite of new generation technologies making the Microdome projectors essentially obsolete.

[ppppenguin]

Eidophor was one of those crazy ideas that happened to work. And it had to be continuously pumped.

[Brianc]

It was even possible to change the heater/cathode assembly in the field! However, they were rather large bits of kit!

[Aerodyne]

This looks exactly like the mirror drum shown as a drawing on p.24 of my Newnes Television and Short Wave Handbook, 1934 (F.J. Camm). There is a photograph of a similar but not identical mirror drum 'receiver' in the photo insert between pp. 40-41 of the same book.
Amazing to think this has survived from, at the very least, the early 1930s and possibly longer.

Tony

[peter scott]

I don't think this is a prototype item as described.

Perhaps

[ed731pdh]

Found this entry; https://en.wikipedia.org/wiki/Eidophor

[peter scott]

Found this entry;  https://en.wikipedia.org/wiki/Eidophor

Yes, now that is a proper mirror drum!