GB475047A - Improvements in or relating to electron discharge devices - Google Patents

Abstract

475,047. Cathode-ray tubes. BAIRD TELEVISION, Ltd., JONES, V., and WILLANS, P. W. May 11, 1936, No. 13302. [Class 39 (i)] A discharge tube has a storage grid and an equipotential grid which is parallel and in close proximity to the storage grid and is at a high potential with respect to the cathode, and a wide homogeneous electron beam is adapted to pass through both grids and be modulated to a varying extent over its cross-section by the storage grid, the modulating potentials on the various elements of which vary in accordance with an electron or optical image. The mosaic elements of the storage grid may be photo-electrically or photoconductively or photo-voltaically active. Means may be provided for discharging the potentials on the mosaic elements.. The elements may be mounted through high-resistance material on a conductor, the potential of which extinguishes the electron beam when the storage grid is not illuminated. Alternatively, an intermittent or continuous electron beam may be used. The storage grid may be negatively biassed with respect to the cathode, but when it is photo-voltaically active it may be at a small positive potential. The storage grid may not be light-sensitive and the potentials thereon are then generated by impinging electrons produced by a photo-cathode, on which the image is projected, or by a scanning cathoderay modulated by television &c. signals. The mosaic elements may be charged positively due to secondary emission or negatively. The scanning ray may impinge on an auxiliary electrode, electrons from which are accelerated and focused on to the storage electrode. In one form, an image 1, Fig. 1, is focused on to a storage grid 3 which controls a homogeneous beam generated from a plane cathode 4 which may be indirectly-heated or photo-electric. The beam passes through the equipotential grid 6 to the fluorescent screen 5. The grid 6 may be on either side or on both sides of the storage grid. Electric or magnetic focusing and accelerating means may be provided between the electrodes 3, 4 and 5, 6. In another form, an image 2, Fig. 2, is focused onto a photocathode 7 from which electrons are focused on to the storage grid 3. In a further form, the storage grid is scanned by a modulated beam from a gun 8, Fig. 3, which may be on either side of the grid 3 or arranged so that the beam passes through an aperture in the cathode 4. The invention may be applied to iconoscopes or image dissectors.