GB1284001A - Signal display apparatus - Google Patents

Abstract

1284001 Cathode-ray tube circuits HEWLETT-PACKARD CO 17 Feb 1970 [24 Feb 1969 7578/70 Heading H4T [Also in Division H1] Signal display apparatus comprises a C.R.T. including display screen 17, writing electron beam gun 11, flood electron gun 13 spaced away from the axis for selectively supplying flood electrons to screen 17 and control means connected to the guns for activating the flood gun subsequent to the deactivation of the writing gun, the flooding being initially at a first energy level within the decay period of the luminous output to increase the light output at the written areas, and subsequently at a second level. The first level may be higher than the second level (Fig. 2d, not shown), the second level primarily being sufficient to post fog photographic recording film. The screen may be ZnS with Cu phosphor, post accelerator electrode 35 a continuous conductive layer or spiral strip on the inner or outer envelope surface, and the flood gun preferably behind mesh 31 and comprising convex electrodes (Fig. 3, not shown) producing divergent flood beams. Electron emitter (51) may be 0À50 inch radius and indirectly heated, concentric spherical mesh (57) being of a greater radius by 0À010 to 0À100 inchs, e.g. 0À55, the mesh size typically passing more than 50% of emitted electrons. Divergence is independent of biasing potentials, typically - 20 and - 5 to -10 volts, and may be 35 to 40 degrees for cathode radius of 0À155 inch, anode radius 0À338 inch and anode aperture 0À276 inch. The anode and cathode spherical surfaces may also be approximated in stepwise fashion using concentrically stacked flat sections of decreasing diameter. For small electrodes in close proximity, an anode with small aperture and no mesh may be in combination with a flat cathode surface.