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Sometimes you read about old technology, get to the end of the sentence, and have to read it again because it sounds so completely ludicrous you can't quite believe it actually worked.

Anyway Eidophor projectors are what they used for Apollo Mission Control.

en.wikipedia.org/wiki/Eidophor

The Eidophor used an optical system somewhat similar to a conventional movie projector, but substituted a slowly rotating mirrored disk or dish for the film. The disk was covered with a thin film of transparent high-viscosity oil, and through the use of a scanned electron beam, electrostatic charges could be deposited onto the oil, causing its surface to deform. Light was shined on the disc by a striped mirror consisting of strips of reflective material alternating with transparent non-reflective areas. Areas of the oil unaffected by the electron beam would allow the light to be reflected directly back to the mirror and towards the light source, whereas light passing through deformed areas would be displaced and would pass through the adjacent transparent areas and onwards through the projection system. As the disk rotated, a doctor blade discharged and smoothed the ripples in the oil, readying it for re-use on another television frame.

type of television projector

Contributors to Wikimedia projects (Wikimedia Foundation, Inc.)

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in reply to Jonty Wareing

Christian Vogel
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Christian Vogel
• •
youtu.be/3-BvMcqEc98 I think this is the best overview on how this works I’ve seen…

- YouTube

Auf YouTube findest du die angesagtesten Videos und Tracks. Außerdem kannst du eigene Inhalte hochladen und mit Freunden oder gleich der ganzen Welt teilen.
youtu.be
in reply to Jonty Wareing

Kelsey Jordahl
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Kelsey Jordahl
• •

it is still amazing to me that there was a period of >50 years that it was cheaper and easier to shoot a particle beam at a phosphor screen, steer it with magnets, and scan it 24 times a second across the whole screen while turning it on and off much faster than that, than it was to make individually controllable pixels. And then, it was easier to jury-rig color into the phosphor screen (and the whole upstream system) than to come up with a new design. And it was all run by backward-compatible analog radio signals.

...and also that all of that was the main display technology for digital computers for decades.

in reply to Kelsey Jordahl

evan
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evan
• •

@kajord
Modern digital technology seems so simple by comparison (it surely isn't) than these complex analog solutions -- it makes me wonder how much the rediculousness of the tropes of a mad-scientist's lab, techno-babble in sci-fi, or Rube Goldberg machines seem now, when like, this was peak technology at the time.

(Thought about this watching Back To The Future with my kid, especially around the Doc Brown scenes.)

@Kelsey Jordahl
in reply to evan

khm
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khm
• •

I am trying and failing to remember which science fiction author had a whole bit about how a given technology would have fewer and fewer moving parts, and a perfectly mature technology would just be a highly engineered block of matter that did whatever its function was

CC: @kajord@hachyderm.io @jonty@chaos.social

@Jonty Wareing @Kelsey Jordahl
in reply to Jonty Wareing

Matt Large
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Matt Large
• •
In Mission Control these were only for the low res “video” screens on the ends of the big wall. Actually just the right side for early missions. How the other main screens worked is even more crazy!!!!!
in reply to rk: it’s hyphen-minus actually

PulkoMandy
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PulkoMandy
• •
@rk @mattlarge there was another room the same size as the control room, called the "batcave", with a team of people using a mix of slide projectors, focused light beams and various other projection devices to overlay pictures (of the moon surface, the route between eartheand moon, ...), text and datapoints (the lander or spacecraft position, ...) in real time
@Matt Large @rk: it’s hyphen-minus actually
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