Some aspects of a cathode-ray-tube projector for large-screen television in cinemas

The paper deals with the development of a large-screen cathode-ray-tube projector employing the Schmidt optical system and a back-aluminized projector tube, and is concerned mainly with the design of the optical system, the tube and the associated electron-optical components. A brief description is given of developments which took place prior to the advent of the back-aluminized tube. The performance of the Schmidt optical system and the factors influencing the choice of aperture ratio are discussed; in the present application a 17.5-in f/1 system is used in conjunction with a 9-in projection tube. Some aspects of the projection tube are described, reference being made to the electron gun, spot-size measurement, gas-focusing effect and problems associated with the fluorescent screen. Particular attention is given to the reduction of aberrations introduced by the magnetic focusing and deflection systems. The application of the 8-pole pincushion convertor is investigated.