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Flat CRT from Sinclair

Wireless World, April, 1981.
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Clive Sinclair of Sinclair Research Ltd has recently announced the successful development of a flat cathode ray tube which will be incorporated into a miniature TV set. The set will include VHF/FM radio and may be switched to most international TV standards, making it of universal use.

The Sinclair tube measures about 4 × 2 × ¾3/4 in. and is three times brighter, requires between one quarter and a tenth of the power and is half the volume of a conventional CRT with the same size screen. It is assembled from just two sheets of glass, a flat front plate and a vacuum-formed backing plate. The phosphor screen is coated on the inside of the backing plate and is viewed through the front face from the same side that the electrons strike. This gives a brightness of more than double that of a conventional CRT with the same beam energy. In addition to the horizontal and vertical deflection plates there is a third set between the phosphor screen and the front face to bend the electron beam on to the screen.

To correct for distortion the screen height is reduced by as much as half while the width is kept constant. This narrows the angle subtended by the electron beam and the picture height is restored optically by using a horizontal Fresnel lens to give an effective picture size with a 3 in. diagonal. Other distortion is eliminated by careful attention to the modulation applied to the deflection plates.

The tube has been produced in Sinclairs pilot production plant at St Ives, Cambridge but it has just been announced that a full production plant is to be commissioned in Dundee by the Timex Corporation. Timex were awarded the contract by Sinclair because of their expertise in automatic production. It is expected that at the end of the first phase the capacity will exist to produce the tubes at the rate of a million a year.

The Microvision TV set which will incorporate the tube is also to be produced by Timex and should be on the market by mid-1982. Although the exterior design of the set has not been completed, some design models have been produced to show that the set will be about 6× 4 ×1 in. or about the size of a paperback book. It will retail for about £50.

Further developments for the tube depend upon the extremely high brightness which may be achieved. This leads to its suitability for use in projection systems. A monitor for the Sinclair personal computer is high on the applications list, as is a colour projection TV which would incorporate three of the tubes and the associated electronics in a projector about the size of a shoe box to produce a picture on a wall screen with a 50in. diagonal.

FTV1 exhibit.

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