Phil Hobbes: State of the art electro-optical design in 1938

You can now get audio cd's with Nipkow disk based color movies on them.

Steve.

That isn't too hard. It's a darkfield moire' system using a fairly coarse grating (like a Ronchi ruling). Light goes in through the ruling, reflects from an oil-coated mirror, and comes back out the same way. The oil mirror (Eidophor) is tipped slightly so that the reflected image is dark when nothing is written in the film.

An electron beam writes on the oil film, leaving an array of surface charge. This causes the surface to deflect due to the electrostatic attraction of the surface charge to the metal underneath. The local tilt of the surface causes the light to be deflected a bit, enough for some of it to make it back through the clear part of the ruling.

The oil film is restored to a uniform thickness by a knife edge as the plate that it sits on rotates.

Of course all this has to be in a vacuum chamber. One gathers that the film was made of some sort of vacuum pump oil, because otherwise the e-gun wouldn't have worked for long.

Cheers

Phil Hobbs

But Phil, the color one uses the Schlieren bars, but writes squiggles in the oil to form a diffrative optic. Evidently it can do color with one white source, no dichroics, and uses magenta and green as primaries...

The basic Eidophore I do understand, that's easy using a field stop and diffraction.. It is the single lens color one that is baffling...

Steve

The one I saw used three separate optical systems.

Cheers

Phil Hobbs

Oh, and the other one used a colour wheel.

Cheers

Phil Hobbs

After some digging, it is GE's Talaria that uses the magenta and green. They do use Dichroic filters in a X-Y array. Vertical squiggles of the electron beam select green, and horizontal squiggles select magenta filters.

Steve

Fun. I love mixed-technology systems.

Cheers

Phil Hobbs

About the same lifetime as the lamp in many projectors today.