Slimmer TV

The conventional TV picture tube, whose monstrous bubble of vacuum is responsible for most of the bulk of the TV cabinet, may be on its way out. Electronics men have long dreamed of shrinking the tube to a flat plate not much bigger than the picture. The latest Electronics describes one such tube. Designed by the Electronics Division of Willys Motors, it is in an advanced experimental stage (see diagram).

In the standard TV tube, the picture is formed by a slim beam of electrons scanning back and forth across the phosphor on its front face, like a garden hose washing a wall. The Willys tube works on the same general principle, but it has no large empty space. It is made of two glass plates an inch or so apart, with a vacuum between. The electron beam enters from an upper corner. The electrons move horizontally between the glass sheets and stream past metal "deflection plates."

If one of these plates carries the proper electrical charge, it deflects the electron beam downward. On their way down the electrons pass horizontal deflection plates and are turned sharply against the forward glass plate, which carries a picture-forming phosphor. When the voltage on both sets of deflection plates is changed simultaneously, the electron beam scans the phosphor, sweeping across it and producing a TV picture.

The Willys tube is about three inches thick. It might cut the size of a TV cabinet by more than half. It is not on the market yet, but the Navy is adapting it to instruments for displaying radar maps and other information to airplane pilots.

An even more radical flat tube under development by General Electric Co. gets rid of the vacuum, and it has no electron beam either. It consists of a sheet of "electroluminescent" phosphor that glows when it is excited by an electrical voltage. The phosphor is sandwiched between a matrix of horizontal and vertical wires. If there are 500 running in each direction there will be 250,000 points at which wires cross. These intersections can be made to glow by impressing the proper voltage on the wires. If the voltages are changed rapidly, the spot of light scans the screen, forming a TV picture.

Picture screens of this sort need have hardly any thickness, and they can be scaled up, theoretically, to movie-screen size. But G.E. warns the public not to expect them on the market for a while.

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