Early Color Television
Eidophor was a projection system developed by a group of Swiss scientists. It was adapted by CBS for use with its field sequential color system. Peter Yanczer's excellent article describes the technology.
Popular Science, February 1946
Dichroic Wheel. Note the differences in the colors when light is transmitted through (left) and reflected off (right side of right picture)
Color wheels from a Swiss GRETAG Eidophor projector. Note
Here is a story about operating an Eidophor from Mark Sutton from Portland:
Quite a machine, that, I used to run one that was in a room suspended 60 feet below the roof of The Kingdome (King County Domed Stadium in Seattle). It went up in the mid '70s (when the stadium was built) and was replaced with an early Mitsubishi Diamond-Vision screen in the early '80s. Access to the room was either by climbing up to the roof and walking some stairs that ran along the outside of the dome, then inside and down a caged ladder to the room - or - by riding a Spider-Staging lift (think "window-washing lift") from the arena floor up to the projection room. But that took like 15 minutes each way so it was faster to run the stairs. Greitag considered it one of the two worst locations (for access) in the world, I don't remember what the other one was. Maybe up on The Matterhorn or something like that.
When the projector went in, it had to compete with reflected lighting from the field, which was lit to about 50-70 fc initially. Then they had the All-Star game there and NBC required better (more) lighting so the screen got badly washed out with only about a 2:1 contrast ratio. We got a new set of lenses to reduce the projected image size and concentrate the light, then had to mask off the unused parts of the screen. But it was a nice image if the stadium was darkened for concerts or other events. Initially the signal was fed up NTSC composite video but later some more wire was pulled and it was fed RGB so the resolution was better.
One time a new replacement Xenon lamp failed shortly after installation. It got hot and the envelope failed, the lamp exploded (those things are under pressure when operating) and little bits of orange-hot quartz glass sprayed all over the little projection room. The room had plexiglass walls so the glass particles didn't rain down on the baseball players below - we were roughly above second base. I was in there with another operator, leaning against the cabinet when the lamp blew. It was loud, I was told that it sounded like a grenade had gone off down in the seating area. I was up on the roof of the room before the other guy, and he was leaning against the ladder. I think I jumped over him.
The other fun thing with this projection room was, the air conditioner dribbled off a large amount of condensate (tens of thousands of fans exhaling water vapor and we were up in the stagnant layer). The baseball players got rained on and thought we were spitting on them. So we took a couple of 5-gallon buckets up to collect the drainage. I got a bag of water balloons and would stick one at a time over each drain tube to collect the water (the units were rooftop mounted) and would accumulate a few dozen water balloons in a bucket and then do some "target practice" when the stadium was not occupied. The field crews were annoyed about all the brightly colored balloon fragments in the Astroturf but never figured out the source.
Interestingly, there were 3 other Eidophors in the county at the time. The Boeing Space Center used them in their Space Flight Simulator.
After The Kingdome replaced the Eidophor with the Diamond Vision (I think World Stage bought the Eidophor), the tower hung from the roof of the dome for several years. They finally decided to get it out of there. Somebody bought it - it was a nice, beefy section of transmitter tower, after all. In the process of lowering it from the roof, something gave way and it dropped to the arena floor (and somewhat into the arena floor) and so became scrap metal. Several years later, of course, they did that with the whole dome and put a new stadium on its site.
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