In article ,
"William Sommerwerck" wrote:

If you want to take a look at a truly *bizarre* video projection
technique, find out how an Eidophor works. Or worked; I really
don't know if they're in business these days. Think about vacuum
pumps, rotating oil-covered mirrors, Schlerin optical systems,
ten-kilowatt xenon short-arc lamps, and little air-locks for
replacing the filaments while in operation, all in one box. Times
three, of course, for color.

Actually, I think Eidophor color used a rotating wheel.

There were both kinds: a monochrome one with a wheel (mostly for
computer output purposes), and a three-beam one -- R, G, B -- which
worked better for "regular" TV.

The three-color ones were capable of producing a 65-foot-diagonal image
in which you could see the NTSC color subcarrier crawling up the screen
(demonstrating really good bandwidth and focus). They were also the only
imaging devices of that time that could properly display the "I" and "Q"
bars of a composite color bar test pattern. That was because the light
source was a full-spectrum arc, and dichroic filters were used to
separate the primaries, so it was possible to select the three primary
colors with great precision (you can't do that if you start with
phosphors).

Isaac (who once made an emergency air trip from LA to Houston because
somebody had let one of the dumpster-sized things swing 30' into a
concrete wall while it was being hoisted into place)