Improvements in Image Iconoscopes by Pulsed Biasing the Storage Surface

In storage-type television camera tubes using high-velocity electrons for scanning, such as the iconoscope and image iconoscope, the storage surface is stabilized to an equilibrium potential by secondary emission. A number of undesirable characteristics, such as spurious signals, absence of "black-level" information, and relatively low efficiency, are usually associated with tubes of this kind. However, these disadvantages are considerably reduced if the mean potential of the storage surface is shifted negatively. A method is investigated for obtaining such required potential shift by periodically irradiating the storage surface with high-velocity electrons while simultaneously reducing the collector potential, these periodic processes being carried out during suitable intervals in picture transmission, such as the frame-blanking period. Application of this principle has been most successful in cases where the picture is projected intermittently as in the "memory-scanning" method of film transmission, but for continuous pickup the advantages are only partly attainable.