Jenkins Prismatic Rings

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Mechnical Television

Jenkins Prismatic Rings

Early Television

Courtesy of Luc Sirois

Jenkins used prismatic ring scanners in his early Radiovision experiments (1924-25). Here is a description of how it worked:

Early Television

These machines are primarily used in radio transmission of photographs; employ four overlapping prismatic disks or "rings" in both the sending and receiving machines. Either a transparent or an opaque picture is used in the sending instrument; and in the receiving camera a filament lamp, modulated by the incoming radio signals, recorded on a photographic negative plate.

In the sending machine the picture is projected with a magic lantern (1) through four overlapping prismatic rings, (2) of of which in rotation sweep the picture vertically across the light sensitve cell, at the same time the image is moved laterally by the other pair of prisms. The different light values of the picture are changed in electric values in the light-cell (4) and broadcst. A rotating perforated disk (3) interposed between the lens and light-cell, produces a pulsating direct current which can immediatly be amplified thorough the usual radio transformers, on its way to the broadcasing set.

Early Television

Different designs used 1, 2, 3, or 4 disks. This system was abandonded by Jenkins in favor of Nipkow disks.

Jenkins Prismatic Disk in the Museum's collection

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