Scophony

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Scophony was a sophisticated mechanical television system developed in Britain, which used mirrors mounted on high-speed rotating drums to project an image upon a screen.

In 1938 the Scophony company demonstrated three types of 405 line mechanical television receivers at the Radiolympia exhibition in London: a home receiver, with a picture area of approximately 24" x 22" and two systems intended for theater operation, one producing a 6ft x 5ft image and the other a 9ft x 12ft image.

Several of the theater systems were installed and operated successfully but none of the receivers were sold as production was halted due to the impending war.

Scophony's system used several innovative devices:

A split focus optical system invented by G.W. Walton, developed specially for use with mirror scanning systems. Light beams were focused by crossed cylindrical lenses, concentrating the light in two planes. This allowed the use of smaller lenses and mirrors, thus reducing size and cost. This was particularly important to Scophony since they intended to produce extremely large images.

A light modulator developed by J.H. Jeffree in 1934 and known as the Jeffree cell, a cell filled with a transparent fluid which used mechanical oscillations to modulate the light beam passing through it. It was a substantial improvement over the previous Kerr cell, 200 times as much modulated light being available at the screen.

High speed synchronous motors which could be relied on for 1000 hours of use, some lasting longer without noticeable wear. The Scophony system used two: a low speed scanner which operated at 240 RPM and a high speed scanner which ran at 30,375 RPM for 405 line transmissions or 39.690 RPM for the American 441 line system.