GB727937A - Improvements in or relating to storage electron discharge devices - Google Patents

Abstract

727,937. Cathode-ray tubes. COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL D'USINES A GAZ. March 13, 1953 [March 17, 1952], No. 7007/53. Drawings to Specification. Class 39 (1). In an electron discharge tube in which information is stored upon a storage area of a target as electrical charges and in which signals are derived from the target by a scanning electron beam, the target comprises a marginal area of secondary emissive material which is distinct from the storage area and upon which is a design having different secondary emissive properties. The marginal area serves as a monoscope target and is not scanned in normal operation, but is scanned when it is desired to check the focus of the electron beam. Preferably the marginal area forms a narrow border around the storage area of the target. It may comprise, for example, an aluminium frame upon which a design such as alternate groups of horizontal and vertical lines is formed by carbon, or a marginal area of the target base member may be left unsensitized and provided with the design. The storage tube may be a television pick-up tube of the iconoscope or super-iconoscope type, on a signal storage tube in which signals are recorded on the target by a writing beam, and are reproduced from the target by a reading beam. In this latter type of tube where the reading and writing beams are incident upon different faces of the target a design area may be provided on each side of the target.